Modern-day Miura
- Thread starter JHeinke
- Start date
I didn't consider anything but aluminum. I probably should have. Making this part in fiberglass would have taken as much or more time than aluminum by the time a mold was made, etc. Given my CAD skills are very beginner level, I'm guessing it would have taken as much time for me to model this part in order to 3D print it as to fabricate it. Of course, the next part would be much easier to model as I would have learned something. If I were in the business of making many of the same car model, I would factor that into my approach for making a given part. Given, I'm making just one Miura, I don't mind a time intensive approach if it results in a high quality piece.
Test fit of gauge panel
I bought a Mitler Bros. 2 1/16” two piece hole punch to make the holes for gauges in the panel. First is to drill a ½” hole centered where you want to larger hole, thread the bolt through the hole and use to bring the punch pieces together and make the larger hole.
After grinding back some of the wider weld beads, the gauges were installed. I also made some prototype pieces for adjacent panels and clamped the whole works into place.
The gauges are Dakota Digital HDX. I really like the look of these gauges and especially because there’s no manufacture branding on the faces. The look is clean and functional with nice looking billet bezels. Another thing that lead me to use these gauges is they will work in conjunction with the EFI ECM and thus don’t require a second set of sensors in the engine.
I plan to mount the headlight and AC switches in the panel below the gauges. I’m also trying to work in a couple of AC vents which looks doable. Next step is to work out the top and sides for the console where this gauge panel will actually be mounted.
I bought a Mitler Bros. 2 1/16” two piece hole punch to make the holes for gauges in the panel. First is to drill a ½” hole centered where you want to larger hole, thread the bolt through the hole and use to bring the punch pieces together and make the larger hole.
After grinding back some of the wider weld beads, the gauges were installed. I also made some prototype pieces for adjacent panels and clamped the whole works into place.
The gauges are Dakota Digital HDX. I really like the look of these gauges and especially because there’s no manufacture branding on the faces. The look is clean and functional with nice looking billet bezels. Another thing that lead me to use these gauges is they will work in conjunction with the EFI ECM and thus don’t require a second set of sensors in the engine.
I plan to mount the headlight and AC switches in the panel below the gauges. I’m also trying to work in a couple of AC vents which looks doable. Next step is to work out the top and sides for the console where this gauge panel will actually be mounted.
Dash Console for Gauge Panel
On the Miura, the center dash console housing the small gauges flows downward to seamlessly connect with the center console. As such, I need to make sure I keep this in mind and design in a way to interconnect the two while fabricating the dash console. My idea is to used rounded edges on the dash console that can be matched up with aluminum tubing to carry the rounded edge shape through a decently tight curve to the center console (see pictures in Post #240 for shape I’m trying to replicate).
To get the rounded edges on the dash console sides and top, I hammer formed .050 3003 Al over a ½” round tube using a rubber hammer. Once the sheet formed 180 degrees over the tube, I then clamped the works under a metal bar and bent a flange out 90 degrees to serve as dash panel mount.
Using cardboard to make a template, I was able to determine a good panel outline and mounting flanges for the side panels.
The top panel has curved edges on the sides to then mate up with side panels. A 1 ½” round tube was used to hammer form these edges.
All is good so far, but now for the hard part. There are 3 radiused edges now converging at each top corner that need to blend together. Given this is all happening in a very small area, this makes for a real metal shaping challenge. I could make a couple of wooden hammer forms and whack some aluminum into the desired shape but that feels more time consuming than I’d like. I decided that making these pieces without a hammer form was easier tackled in multiple pieces but welding on too small pieces usually turns into melted aluminum on the floor. So I did it in 2 pieces and still ended up melting a couple of them into waste while attempting tack welds. Here’s one of the pieces successfully welded to the top.
The second piece was formed and welded to side panel and then carefully hammered and trimmed to blend with the other while the side and top panels were clekoed together. Once a good fit and shape was achieved, the corners were welded up and then welds filed for final shape.
I decided to use counter sunk rivets to join the top and side panels to avoid panel warpage that is hard to avoid when welding flat thin aluminum surfaces together. Rivnuts were added to the mounting flanges to complete the console.
I plan to finish the gauge panel in wrinkle powder coat and the dash console will get upholstered in leather but those finishes will wait till much later in the project.
On the Miura, the center dash console housing the small gauges flows downward to seamlessly connect with the center console. As such, I need to make sure I keep this in mind and design in a way to interconnect the two while fabricating the dash console. My idea is to used rounded edges on the dash console that can be matched up with aluminum tubing to carry the rounded edge shape through a decently tight curve to the center console (see pictures in Post #240 for shape I’m trying to replicate).
To get the rounded edges on the dash console sides and top, I hammer formed .050 3003 Al over a ½” round tube using a rubber hammer. Once the sheet formed 180 degrees over the tube, I then clamped the works under a metal bar and bent a flange out 90 degrees to serve as dash panel mount.
Using cardboard to make a template, I was able to determine a good panel outline and mounting flanges for the side panels.
The top panel has curved edges on the sides to then mate up with side panels. A 1 ½” round tube was used to hammer form these edges.
All is good so far, but now for the hard part. There are 3 radiused edges now converging at each top corner that need to blend together. Given this is all happening in a very small area, this makes for a real metal shaping challenge. I could make a couple of wooden hammer forms and whack some aluminum into the desired shape but that feels more time consuming than I’d like. I decided that making these pieces without a hammer form was easier tackled in multiple pieces but welding on too small pieces usually turns into melted aluminum on the floor. So I did it in 2 pieces and still ended up melting a couple of them into waste while attempting tack welds. Here’s one of the pieces successfully welded to the top.
The second piece was formed and welded to side panel and then carefully hammered and trimmed to blend with the other while the side and top panels were clekoed together. Once a good fit and shape was achieved, the corners were welded up and then welds filed for final shape.
I decided to use counter sunk rivets to join the top and side panels to avoid panel warpage that is hard to avoid when welding flat thin aluminum surfaces together. Rivnuts were added to the mounting flanges to complete the console.
I plan to finish the gauge panel in wrinkle powder coat and the dash console will get upholstered in leather but those finishes will wait till much later in the project.
Neil
Supporter
Are those big sharp corners on your instrument cluster going to pass inspection? Looks dangerous to me.
Hmmm...interesting question. First off, it's driver/passenger safety I'd worry about, not inspection (because there isn't really a "safety" inspection from my experience with homebuilt cars). I'm guessing the pictures shown don't do a good job of showing the context so I took some measurements.
It's 36" from the seat back to the upper corner of that dash console from the seating position I'd use. The seats are fairly inclined backward as you'd expect in a car with about a 40" roofline. When seated with my head in a driving position, it's 25" from the tip of my nose to that upper corner. With no seat belt restraints and a sudden stop, the driver could conceivably hit their head on that corner. But with shoulder restraints, 25" is a long way and most likely not possible. It's a similar situation for the passenger as well.
Ok, seat belts it is, but that's always the case in cars I drive. Also with the inclined seating positions, gravity must be overcome for occupant forward travel. With these two considerations, I'm not concerned that the dash console presents any real dangers.
Neil
Supporter
OK, I hear you but I would not do it..
Any updates on this build?
I do have a small update in that the coolant system plumbing is now complete. I decided to use a combination surge and coolant overflow tanks that are siamesed together. This combination tank is now mounted on the front bulkhead as high as possible.
Two reasons for this location: 1) trying to put as much weight up front as possible to overcome the rear wheel weight bias from mid-engine placement, and 2) given the electric water pump placement up front, it minimized the number of “steam/bubble” tubes to 1 that would need to traverse the length of the chassis.
If you look closely in the above picture, the -4 tube from upper radiator hose to surge tank is visible along with the 5/8” hose from bottom of the surge tank to the pipe just upstream of the electric water pump intake. Not visible is -4 tube from the highest point in the coolant system at the engine that runs up the middle bottom of the chassis to the surge tank.
That’s all the progress I’ve been able to make on the Miura over the past couple of months. I do however have a very good reason for this. As the winter snows were falling, my Shelby Cobra with a bum engine started to beg from some attention and a fix for the engine. I decided to try to get it running again after more than a year of sitting and before the summer driving season arrived.
After pulling the engine and tearing it down, what I thought would be a spun rod bearing turned out to be a scored piston. The rear most piston on the passenger side of the 5.0L SBF had tried to weld itself to the cylinder wall so it didn’t turn out to be an easy part replacement fix. Given this, I decided to upgrade to a 347 cid SBF engine and a new Tremec TKX transmission to resolve the over rev condition that was the root cause of the scored piston.
I think this new engine with more than 100 additional horsepower should be just what the doctor ordered. While waiting for the new engine and in anticipation for more punch, I decided to check the posi. It turns out, the 9” rear end was equipped with a Ford Trac-lok posi unit that was completely worn out. This was replaced with an Eaton Tru-Trac helical-gear style, limited-slip differential.
I guess you can see that I was distracted from Miura project in a big way and that’s the reason why the Miura progress has been slow. The new Cobra engine should arrive any day now so the Miura has a couple of more weeks to collect dust before it will get any attention.
Moving forward on Miura project again
I’m back on the Miura project again. I’m happy to report that the Cobra is running great and has been very fun to drive over this past summer.
My short-term goal for the Miura is to get to that ever-important milestone of “initial engine startup” and to drive it a bit as a “go-kart” to prove out some of the homebuilt drive train components. To help guide the effort, I put together a checklist of 20 items that needed to be accomplished prior to being able to move the Miura under its own power. Some of the items will take some effort, some are small but the main thing in common is that the engine couldn’t be in the chassis to complete them. So, I once again pulled the engine/transaxle and got to work.
Wiring harness pass through: To provide transaxle clearance, I had to cut away a portion of the chassis and remake it. This is a great place to route the 4 bundles of wires that are needed to go into the engine compartment. The panel replacement pieces were welded and bonded into place and then some small panels were made to let the wire harnesses pass through.
With this chassis fix now complete, the engine mount could also be welded onto the chassis rail.
Notch in transaxle case: The drivers side drive axle runs very close to the transaxle case and the axle looks like it could make contact on full suspension compression. So, I fastened the transaxle case down on the mill and carved out a notch.
Replace damper/serpentine pulley: The standard Coyote crankcase pulley is a double belt style with the inside belt driving the A/C and outside pulley driving the alternator, water pump, and power steering. To fit the Coyote engine in the Miura chassis, the outside pulley needed to be removed to clear the frame rail. I’ll be using an electric water pump and no power steering so only the alternator needs to be refit.
I did all that about a year ago but in the meantime started to worry that the cut down pulley wouldn’t be adequate to drive both the A/C compressor and alternator. The standard Coyote damper pulley has an outside belt drive ring pressed over rubber to the inside hub. With the second belt part of the pulley machined off, more than half of the rubber surface area was removed and I was worried about the outside ring separating from the hub.
So, I phoned up tech support at ATI to see if a damper for a different engine might be made to work. It turns out the earlier 4.6 modular engines that came in late 90’s early 2000’s Mustangs used a single belt drive of the same diameter and had the same crankshaft and seal sizes as the Coyote but the spacing had the damper protruding less out of the engine timing cover. After taking a bunch of measurements, I determined that adding a .180 inch spacer between the timing chain gear and the damper would correctly line the belt up and give just enough clearance so the damper wouldn’t hit the timing chain cover. The engine is now fitted with a much better damper pulley with no worry of separation as the pulley part is securely bolted to the inner hub.
Well, that’s a few items checked off the list. More to come…
I’m back on the Miura project again. I’m happy to report that the Cobra is running great and has been very fun to drive over this past summer.
My short-term goal for the Miura is to get to that ever-important milestone of “initial engine startup” and to drive it a bit as a “go-kart” to prove out some of the homebuilt drive train components. To help guide the effort, I put together a checklist of 20 items that needed to be accomplished prior to being able to move the Miura under its own power. Some of the items will take some effort, some are small but the main thing in common is that the engine couldn’t be in the chassis to complete them. So, I once again pulled the engine/transaxle and got to work.
Wiring harness pass through: To provide transaxle clearance, I had to cut away a portion of the chassis and remake it. This is a great place to route the 4 bundles of wires that are needed to go into the engine compartment. The panel replacement pieces were welded and bonded into place and then some small panels were made to let the wire harnesses pass through.
With this chassis fix now complete, the engine mount could also be welded onto the chassis rail.
Notch in transaxle case: The drivers side drive axle runs very close to the transaxle case and the axle looks like it could make contact on full suspension compression. So, I fastened the transaxle case down on the mill and carved out a notch.
Replace damper/serpentine pulley: The standard Coyote crankcase pulley is a double belt style with the inside belt driving the A/C and outside pulley driving the alternator, water pump, and power steering. To fit the Coyote engine in the Miura chassis, the outside pulley needed to be removed to clear the frame rail. I’ll be using an electric water pump and no power steering so only the alternator needs to be refit.
I did all that about a year ago but in the meantime started to worry that the cut down pulley wouldn’t be adequate to drive both the A/C compressor and alternator. The standard Coyote damper pulley has an outside belt drive ring pressed over rubber to the inside hub. With the second belt part of the pulley machined off, more than half of the rubber surface area was removed and I was worried about the outside ring separating from the hub.
So, I phoned up tech support at ATI to see if a damper for a different engine might be made to work. It turns out the earlier 4.6 modular engines that came in late 90’s early 2000’s Mustangs used a single belt drive of the same diameter and had the same crankshaft and seal sizes as the Coyote but the spacing had the damper protruding less out of the engine timing cover. After taking a bunch of measurements, I determined that adding a .180 inch spacer between the timing chain gear and the damper would correctly line the belt up and give just enough clearance so the damper wouldn’t hit the timing chain cover. The engine is now fitted with a much better damper pulley with no worry of separation as the pulley part is securely bolted to the inner hub.
Well, that’s a few items checked off the list. More to come…
Firewall Insulation
Given the transverse engine placement locates an exhaust header very close to the mid-engine firewall, I’m guessing this makes heat and sound control even more challenging than in a GT40. My plan is to use a multi-layered approach to keep heat and sound out of the car’s interior. The first couple layers are Lizard Skin spray-on products and the third layer will be stick-on DEI Floor and Tunnel Shield. In addition to this, I’m having the header insulated with Header Shield which is claimed to keep 60% of heat from escaping the header pipe itself.
In preparation for spraying on the Lizard Skin, the firewall surface has been scored with sandpaper and masked off.
In addition, the same spray-on sound and heat control will be applied to the under-chassis channel where the coolant pipes, A/C lines, and wiring harness run from front to back of the chassis. I thought this was needed mostly for heat control as the fuel tank is directly above and I want to keep the fuel as cool as possible.
The sound control product goes on first.
After giving the sound control about 90 minutes to fully dry, I followed by spraying on the ceramic insulation product. I opted for the white color but in hindsight probably should have stuck to black. The one thing going for using different colors is it enabled me to see where coverage was insufficient. This is my first time using Lizard Skin products but I think the application went OK. I’d put the wet consistency right at about soft-serve ice cream level so it more “splatters” out of the gun versus “spraying”. Applying the heat control product felt like frocking a Christmas tree with fake snow but that was probably due to its white color.
Once dried, the Lizard Skin has a firm rubber-like feel with a texture like splatter-on dry wall mud. I used a gallon of Heat Control and a gallon of Ceramic Insulation and this resulted in about 1/16” material thickness once dried. I’m not sure how much spilled liquids would soak-in but my gut tells me it should be coated with either paint or something cleanable as the rough surface would likely be hard to clean.
I plan to lightly sand with 40 grit paper to remove the “high spots” prior to applying the stick-on insulation on top of it.
Given the transverse engine placement locates an exhaust header very close to the mid-engine firewall, I’m guessing this makes heat and sound control even more challenging than in a GT40. My plan is to use a multi-layered approach to keep heat and sound out of the car’s interior. The first couple layers are Lizard Skin spray-on products and the third layer will be stick-on DEI Floor and Tunnel Shield. In addition to this, I’m having the header insulated with Header Shield which is claimed to keep 60% of heat from escaping the header pipe itself.
In preparation for spraying on the Lizard Skin, the firewall surface has been scored with sandpaper and masked off.
In addition, the same spray-on sound and heat control will be applied to the under-chassis channel where the coolant pipes, A/C lines, and wiring harness run from front to back of the chassis. I thought this was needed mostly for heat control as the fuel tank is directly above and I want to keep the fuel as cool as possible.
The sound control product goes on first.
After giving the sound control about 90 minutes to fully dry, I followed by spraying on the ceramic insulation product. I opted for the white color but in hindsight probably should have stuck to black. The one thing going for using different colors is it enabled me to see where coverage was insufficient. This is my first time using Lizard Skin products but I think the application went OK. I’d put the wet consistency right at about soft-serve ice cream level so it more “splatters” out of the gun versus “spraying”. Applying the heat control product felt like frocking a Christmas tree with fake snow but that was probably due to its white color.
Once dried, the Lizard Skin has a firm rubber-like feel with a texture like splatter-on dry wall mud. I used a gallon of Heat Control and a gallon of Ceramic Insulation and this resulted in about 1/16” material thickness once dried. I’m not sure how much spilled liquids would soak-in but my gut tells me it should be coated with either paint or something cleanable as the rough surface would likely be hard to clean.
I plan to lightly sand with 40 grit paper to remove the “high spots” prior to applying the stick-on insulation on top of it.
Davidmgbv8
Supporter
You have to put down good floor protection because it is hell to clean off!
Why sound first then heat? I would have thought heat first to keep from conducting into the metal.
Why sound first then heat? I would have thought heat first to keep from conducting into the metal.
The sound coating prior to the heat coating was explicit in the Lizard Skin application instructions. My assumption is that the heat insulation has a higher heat rating and would protect the sound coating from getting overheated.
Firewall Mounting Bracket
Prior to applying the top layer of firewall insulation, I thought it best to locate and fabricate a bracket that would mount there. For the fuel filter and fuel pressure regulator, I decided to build a combination mounting bracket and heat shield. It is built using 304 SS to minimize the heat transfer through the shield.
I cut and peeled away the Lizard Skin under the mounting pads; a razor knife to score the edge and a wood chisel to scrape away the coating.
I plan to cover the exterior of this heat shield with the same insulation material that will be used across the firewall.
Ok, one more thing off the project checklist…
Prior to applying the top layer of firewall insulation, I thought it best to locate and fabricate a bracket that would mount there. For the fuel filter and fuel pressure regulator, I decided to build a combination mounting bracket and heat shield. It is built using 304 SS to minimize the heat transfer through the shield.
I cut and peeled away the Lizard Skin under the mounting pads; a razor knife to score the edge and a wood chisel to scrape away the coating.
I plan to cover the exterior of this heat shield with the same insulation material that will be used across the firewall.
Ok, one more thing off the project checklist…
Firewall Insulation
The installation of firewall insulation prior to engine start-up is now complete with the addition of a third layer. The first layer was Lizard Skin sound control and second was Lizard Skin ceramic insulation. I took off the high spots of the Lizard Skin using 40 grit sandpaper on a block. Prior to applying the next insulation layer, I spray painted on Lizard Skin top coat paint to get everything back to a black color. Then DEI Floor and Tunnel Shield was applied as a third layer with an effort to minimize seams.
I then used DEI Cool Tape to cover all the edges and seams. I always worry about flammable liquids working their way into and under the insulation and then becoming a fire hazard. The aluminized tape sticks well to the bare aluminum surface of the DEI insulation but not so well to the Lizard Skin. Oh well, I think it was worth a try as something is most likely better than nothing.
The coolant pipes, A/C lines, and wiring harnesses are all re-assembled and back in place. I decided to build a bracket to secure the coolant bubble line so it wouldn’t rattle around on the firewall. Also pictured is the tube carrying hot coolant from a booster pump to the heater core.
Obviously, there is more firewall needed to completely separate the engine compartment from the cockpit. I plan to fabricate this upper firewall after building out a sub-frame for the roof as it will tie into this sub-frame. This additional firewall will likely need all the same insulation treatments as what has already been put in place for the lower firewall. All the additional firewall fabrication is planned for after initial engine startup.
The installation of firewall insulation prior to engine start-up is now complete with the addition of a third layer. The first layer was Lizard Skin sound control and second was Lizard Skin ceramic insulation. I took off the high spots of the Lizard Skin using 40 grit sandpaper on a block. Prior to applying the next insulation layer, I spray painted on Lizard Skin top coat paint to get everything back to a black color. Then DEI Floor and Tunnel Shield was applied as a third layer with an effort to minimize seams.
I then used DEI Cool Tape to cover all the edges and seams. I always worry about flammable liquids working their way into and under the insulation and then becoming a fire hazard. The aluminized tape sticks well to the bare aluminum surface of the DEI insulation but not so well to the Lizard Skin. Oh well, I think it was worth a try as something is most likely better than nothing.
The coolant pipes, A/C lines, and wiring harnesses are all re-assembled and back in place. I decided to build a bracket to secure the coolant bubble line so it wouldn’t rattle around on the firewall. Also pictured is the tube carrying hot coolant from a booster pump to the heater core.
Obviously, there is more firewall needed to completely separate the engine compartment from the cockpit. I plan to fabricate this upper firewall after building out a sub-frame for the roof as it will tie into this sub-frame. This additional firewall will likely need all the same insulation treatments as what has already been put in place for the lower firewall. All the additional firewall fabrication is planned for after initial engine startup.
Transverse Transaxle Anatomy
It’s time to do a full transaxle assembly complete with gaskets and sealing so it will hold oil. As a reminder, this is a one-off custom built transaxle made for transverse placement of a Coyote V8 in the chassis. So I’ll try to include lots of pictures for those interested in how a transaxle of this nature works.
Given the limited width between frame rails, the flywheel and clutch assembly are fit very tight to the engine block. A thin flywheel was custom made to minimize space requirements and the clutch is a standard 10.5” unit commonly used with SBF engines. A custom shaft connects the clutch to a transfer gear.
The side of the bellhousing closest to the transmission is machined flat to allow the transmission to fit at zero clearance. The starter mounting flange cast into the Coyote engine block has been cut off and the webbing notched as the transmission is located right next to the engine block. Showing this, it’s probably more obvious as to why Lamborghini made a single casting for engine and transaxle for the original Miura.
The starter was re-located to the other side of the engine secured with bellhousing bolts extended beyond the block to secure it. The Coyote block has a small access hole in this webbing and it was enlarged enough for the starter nose to fit through and engage the ring gear. An engine mount is hung off the bellhousing and secured with 3 of the bellhousing bolts.
The transmission is a 5 speed Tremec TKO. The input shaft is shortened and customized to hold a transfer gear. A custom plate is added to the transmission front to hold the input shaft bearing and to seal the transmission from the transfer case.
The tailshaft housing is replaced with custom machined billet housing. The machining on this housing had to be very precise as it holds the secondary gear shaft and overdrive gear set. The shift mechanism was converted from a lever style to a shaft style. A custom billet housing was required to provide clearance for exhaust headers to pass by. The tailshaft was shortened and customized to hold the small gear for the final drive.
The bellhousing is connected to the transmission via a two gear transfer case. The 2 piece transfer case housing is a structural component as the transmission bolts into it. A McLoed hydraulic throw-out bearing mounts to the transfer case.
Power from the crankshaft is moved through the transfer case via two custom 11” helical cut gears. These gears are mounted on opposing Timken roller bearings with races mounted in the housings. These gears are made lighter via the circular lightening holes in them. Given their large diameter these transfer gears are still fairly heavy. The transmission syncros were upgraded to carbon fiber units as they need to slow the momentum in these transfer gears during shifting.
Once the transfer case is mounted on bellhousing, the transmission fits tight to the engine block. It’s so tight the transmission must be mounted to transfer case back plate prior to mounting it to the bellhousing. I learned this when I tried a different assembly sequence and it didn’t work.
The outer transfer case housing was machined from a large piece of billet aluminum. The circular pieces with pinch nuts on them are adjusters so a pre-load can be placed on the roller bearings behind them. Shaft rotation direction is key in the transfer case design here in order to get 5 forward gears and not 5 reverse gears. The two gear transfer case rotates the transmission clockwise given the transmission is running parallel and reverse direction of the crankshaft. Some transfer cases use a chain which if used in this situation would have required a reversing gear. A decision was made to use transfer gears instead of a chain to keep it simpler.
I’ll continue this transverse transaxle anatomy to include the final drive portion in a subsequent post. While I’ve been involved in the making of this custom transaxle and am doing the assembly now, I can’t really take credit for the design, engineering, and machine work. Pete Aardema and Kevin Braun collaborated on all the complex technical stuff after Pete and I sketched out a rough layout on a bar napkin.
It’s time to do a full transaxle assembly complete with gaskets and sealing so it will hold oil. As a reminder, this is a one-off custom built transaxle made for transverse placement of a Coyote V8 in the chassis. So I’ll try to include lots of pictures for those interested in how a transaxle of this nature works.
Given the limited width between frame rails, the flywheel and clutch assembly are fit very tight to the engine block. A thin flywheel was custom made to minimize space requirements and the clutch is a standard 10.5” unit commonly used with SBF engines. A custom shaft connects the clutch to a transfer gear.
The side of the bellhousing closest to the transmission is machined flat to allow the transmission to fit at zero clearance. The starter mounting flange cast into the Coyote engine block has been cut off and the webbing notched as the transmission is located right next to the engine block. Showing this, it’s probably more obvious as to why Lamborghini made a single casting for engine and transaxle for the original Miura.
The starter was re-located to the other side of the engine secured with bellhousing bolts extended beyond the block to secure it. The Coyote block has a small access hole in this webbing and it was enlarged enough for the starter nose to fit through and engage the ring gear. An engine mount is hung off the bellhousing and secured with 3 of the bellhousing bolts.
The transmission is a 5 speed Tremec TKO. The input shaft is shortened and customized to hold a transfer gear. A custom plate is added to the transmission front to hold the input shaft bearing and to seal the transmission from the transfer case.
The tailshaft housing is replaced with custom machined billet housing. The machining on this housing had to be very precise as it holds the secondary gear shaft and overdrive gear set. The shift mechanism was converted from a lever style to a shaft style. A custom billet housing was required to provide clearance for exhaust headers to pass by. The tailshaft was shortened and customized to hold the small gear for the final drive.
The bellhousing is connected to the transmission via a two gear transfer case. The 2 piece transfer case housing is a structural component as the transmission bolts into it. A McLoed hydraulic throw-out bearing mounts to the transfer case.
Power from the crankshaft is moved through the transfer case via two custom 11” helical cut gears. These gears are mounted on opposing Timken roller bearings with races mounted in the housings. These gears are made lighter via the circular lightening holes in them. Given their large diameter these transfer gears are still fairly heavy. The transmission syncros were upgraded to carbon fiber units as they need to slow the momentum in these transfer gears during shifting.
Once the transfer case is mounted on bellhousing, the transmission fits tight to the engine block. It’s so tight the transmission must be mounted to transfer case back plate prior to mounting it to the bellhousing. I learned this when I tried a different assembly sequence and it didn’t work.
The outer transfer case housing was machined from a large piece of billet aluminum. The circular pieces with pinch nuts on them are adjusters so a pre-load can be placed on the roller bearings behind them. Shaft rotation direction is key in the transfer case design here in order to get 5 forward gears and not 5 reverse gears. The two gear transfer case rotates the transmission clockwise given the transmission is running parallel and reverse direction of the crankshaft. Some transfer cases use a chain which if used in this situation would have required a reversing gear. A decision was made to use transfer gears instead of a chain to keep it simpler.
I’ll continue this transverse transaxle anatomy to include the final drive portion in a subsequent post. While I’ve been involved in the making of this custom transaxle and am doing the assembly now, I can’t really take credit for the design, engineering, and machine work. Pete Aardema and Kevin Braun collaborated on all the complex technical stuff after Pete and I sketched out a rough layout on a bar napkin.
WOW, just WOW ......fantastic, already made a shortcut to this thread.
did you document any of the GTO build? I can just see a glimpse of it behind this last pic.
love to read thru that one too. ...
did you document any of the GTO build? I can just see a glimpse of it behind this last pic.
love to read thru that one too. ...
Thanks Douglas. There is a build thread on the GTO on the All Metal Shaping forum: C5 GTO build thread
To see pictures on that forum, you need to become a member. No big deal, it's free and frequented by really smart people who provide a bunch of great info there.
