Transverse Transaxle Anatomy (cont.)
While assembling the final drive part of the transaxle, I am reminded of a very important point, there are lots of very sharp edges in there. It’s sort of like putting your hands into a draw full of sharp knives, closing your eyes, and fumbling around to try to locate a specific knife only by feel of the blades. Within 30 minutes or so opening up the final drive unit, I had a half dozen slices across my fingers from just lifting and sorting the parts out. Ok, important safety tip, wear gloves when messing around in a gearbox.
The core part of this final drive is a posi differential unit that’s from a late model Ford Super 8.8” used in the Mustang GT. I’m using an Eaton differential that is a clutch style posi. The first thing you’ll probably notice as different is the helical cut large gear instead of the traditional ring gear.
There is almost no free space within this housing so I spent the better part of a half day using the lathe to machine down the bolt heads and nuts that fasten the large gear to the differential so it would clear the case. The small gear is driven directly from transmission output shaft and is carried on a pair of tapered bearings. This gear set provides a 3.40 final drive ratio. It better be right as I can’t just order up a new gear set out of a catalog.
Once the bearing pre-loads were set with shims, the cases are bolted together to save my fingers from all those knife edges and further damage. To connect the final drive to the transmission, the opening for the splined small gear is slid over the output shaft and bolts go from both directions into the cases. CVs/drive axles mount to the stub axles coming out of the final drive. If you recall from an earlier post, I had to machine a notch into the transfer case so the drive axle would clear it upon suspension compression. You can see the notch in the picture below just above the biscuit mount on transmission.
You’ll probably notice in the pictures above the biscuit mount on the outside of the final drive case in addition to a mount on the front of transmission. The mount on the final drive serves as the rearmost motor mount. To carry the load from the final drive case to the engine block, a special bracket was fabricated. The bracket bolts to the engine where motor mount brackets usually attach and then over the cap that retains the outside bearing on the small gear. The intent here is to make the transaxle and engine one rigid unit that is then supported on 4 biscuit style motor mounts.
There you go, the engine and transaxle are ready to go back in the chassis. They must go into the chassis as a single unit as you can probably surmise from the fact that mounts are shared across them. The main advantage most usually stated for a transverse engine and associated transaxle is that all shafts run in parallel and thus less power loss from turning rotating motion by 90 degrees. The disadvantage is challenging packaging that leads to complexity, lots of complexity.
While assembling the final drive part of the transaxle, I am reminded of a very important point, there are lots of very sharp edges in there. It’s sort of like putting your hands into a draw full of sharp knives, closing your eyes, and fumbling around to try to locate a specific knife only by feel of the blades. Within 30 minutes or so opening up the final drive unit, I had a half dozen slices across my fingers from just lifting and sorting the parts out. Ok, important safety tip, wear gloves when messing around in a gearbox.
The core part of this final drive is a posi differential unit that’s from a late model Ford Super 8.8” used in the Mustang GT. I’m using an Eaton differential that is a clutch style posi. The first thing you’ll probably notice as different is the helical cut large gear instead of the traditional ring gear.
There is almost no free space within this housing so I spent the better part of a half day using the lathe to machine down the bolt heads and nuts that fasten the large gear to the differential so it would clear the case. The small gear is driven directly from transmission output shaft and is carried on a pair of tapered bearings. This gear set provides a 3.40 final drive ratio. It better be right as I can’t just order up a new gear set out of a catalog.
Once the bearing pre-loads were set with shims, the cases are bolted together to save my fingers from all those knife edges and further damage. To connect the final drive to the transmission, the opening for the splined small gear is slid over the output shaft and bolts go from both directions into the cases. CVs/drive axles mount to the stub axles coming out of the final drive. If you recall from an earlier post, I had to machine a notch into the transfer case so the drive axle would clear it upon suspension compression. You can see the notch in the picture below just above the biscuit mount on transmission.
You’ll probably notice in the pictures above the biscuit mount on the outside of the final drive case in addition to a mount on the front of transmission. The mount on the final drive serves as the rearmost motor mount. To carry the load from the final drive case to the engine block, a special bracket was fabricated. The bracket bolts to the engine where motor mount brackets usually attach and then over the cap that retains the outside bearing on the small gear. The intent here is to make the transaxle and engine one rigid unit that is then supported on 4 biscuit style motor mounts.
There you go, the engine and transaxle are ready to go back in the chassis. They must go into the chassis as a single unit as you can probably surmise from the fact that mounts are shared across them. The main advantage most usually stated for a transverse engine and associated transaxle is that all shafts run in parallel and thus less power loss from turning rotating motion by 90 degrees. The disadvantage is challenging packaging that leads to complexity, lots of complexity.
