Graziano Gearing and Drop Gears

[Robert Jones]

I’ve had several Vipers too. It had the 3.07 on a stock and 3.07 on a TT. I had 3.55 on one viper too. Yea the 3.55 gave me that “seat of the pants” kick but I think I liked the stock 3.07 the best. I like a longer first gear. My SL-C never had a stock clutch. It had the Kevlar HCF before the the prior owner glazed the flywheel and didn’t break it in before hammering on it. I just replaced it with a SPEC. SPEC is 70 miles from me. They used my flywheel to make a match for their clutch so if anyone needs a clutch call them. The only clutch’s I know available for our cars are stock Audi, HCF, and SPEC. I don’t think your stock Audi will last long but that does depend on how you drive and how sticky your tires are. With stock clutch I recommend no R compound tires but the car really needs them to hook at all.

The reason for my post is really wanting to figure out what I have for my own information but also to program the AIM.

 

[Robert Jones]

Anyone else?

 

[Neil]

Ok, I have to ask "What are drop gears?"

 

[Ken Roberts]

Ok, I have to ask "What are drop gears?"

The search feature on here will answer that question.

 

[Neil]

The search feature on here will answer that question.

The search turned up a zillion "drop gear" references but I still don't know what it means. Is it a British term?

 

[Jeff W]

A drop gear is a replacement gear set to change the ratio of the Graziano, which is geared for a higher revving V8 or -10, to allow lower revving US V8s to run at reasonable RPMs, particularly at cruise. IOW - if the V10 Graz ran 70mph at 3200 RPM it would be undesirable to use the same ratio on a lower rev US V8, so drop gears can change that to say 2100 RPM at 70. I swapped mine out for a 1.04 gear and a better overdrive ratio.

The very first post in this thread explains it pretty much the same way. It's a fairly well-used term.

 

[Joel K]

Neil,

That’s a good question. Not sure where the term came from, but seems like a common term for mini-coopers. I found this simple definition…

Drop Gears - Transfer gears (primary, idler and input gears)

• It briefly goes like this - the crankshaft provides drive through the ‘drop gears’ (primary gear, idler gear, and input gear) into the gearbox. The drive into the first motion gear (some call this fourth gear) transfers to the big one-piece gear (laygear), then back into the individual gears on the mainshaft.

So I think it’s just another name for a set of Transfer gears. As Jeff pointed out, by changing the drop gears, it changes the ratio of all the gears in the transaxle. Equivalent to changing the rear diff ratio.

 

[Neil]

Neil,

That’s a good question. Not sure where the term came from, but seems like a common term for mini-coopers. I found this simple definition…

Drop Gears - Transfer gears (primary, idler and input gears)

• It briefly goes like this - the crankshaft provides drive through the ‘drop gears’ (primary gear, idler gear, and input gear) into the gearbox. The drive into the first motion gear (some call this fourth gear) transfers to the big one-piece gear (laygear), then back into the individual gears on the mainshaft.

So I think it’s just another name for a set of Transfer gears. As Jeff pointed out, by changing the drop gears, it changes the ratio of all the gears in the transaxle. Equivalent to changing the rear diff ratio.

OK, thanks. It is simply an overdrive gear.

 

[Jeff W]

I wrote an entire response about how it's not really an overdrive...then I remembered the old-school second shifter that did pretty much did the same thing and deleted it. Never worked on one and probably only ever been in pickup that had it, did that come off the engine or the tailshaft output?

 

[Joel K]

The way I interpreted it, the Drop Gears are the first set of gears that take the drive shaft and “Drop(reduce)” the RPM from the drive shaft into the trans. The drop gear ratio directly affects the ratio of all the drive gears in the trans.

For example, HCF sells a pair of drop gears which reduces the overall ratio of all the gears in the Graz transaxle, in addition they sell an overdrive gear for sixth gear with replaces the existing 6th with a taller gear.

OK, thanks. It is simply an overdrive gear

 

[Howard Jones]

My guess is that the design is chosen by the transaxle manufactured to allow the same overall GRBX to be used in vastly different power train configurations like a high revving V12 or V10 and a lower revving V8 or V6. Selecting the 'drop gear" changes the entire gear ratio set and is much simpler and less expensive than making and installing a different ring and pinion gear.

 

[Johan]

One reason, and the most important is its a lot easier to change drop gears than change ring and pinion on both front AND rear axles since the Graz is built for 4WD.

 

[Howard Jones]

Johan, Ya I forgot about the 4WD aspect, That's more than likely the reason they did it. So there ya go guys that's why!

 

[Neil]

It sounds to me as if "drop gears" are a transaxle equivalent to the old hot rod "quick- change" differential.

 

[Robert Jones]

Just to update. So I assumed I had the older version of the drop gears based on this chart someone so graciously figured out. I used the ratios for the 1.038 gears and put into the precalc math channels in my AIM MXS Strada and it’s reading all my gears correctly now.

 

[Mark B.]

Has anyone talked with HCF recently? I messaged them on their website last week and DM'd John a few weeks back but haven't heard back. Trying to get a set of drop gears for my Graz.

 

[Robert Jones]

I messaged several times to inquire about the 0.76 gearset but I have yet to hear back. Messaged both he and Price. I you get any response please let me know.