cmnsnse

I can loan out my spare tranny, even with a drive shaft if needed.

I'd love to see a rear end tranny, with a small displacement v-8 up front . . .

Gernby

Why not just shoot for DUAL F20Cs? Could you imagine an AWD dual F20C S2000...

S2000_Europe

What about the BMW Z3 M rear end?, I do now the spec but the Z3 is smaller than the S2000 so should have a "nice" rear end size and capable to resist enough horsepower

Yellow Streak

[QUOTE]Originally posted by S2000_Europe
[B]What about the BMW Z3 M rear end?, I do now the spec but the Z3

Gernby

This is another long shot, but what about the Toyota Supra rear end? I know they were capable of handling a lot of power, but I have no info about their gear ratio.

Busch

RICK, I don't have any spare parts, but might be interested in being a guinne pig for the rear end work. Let me know if I can be of assistance

E30M3

You can get the M differentials in various ratios. It's the same workhorse rear end BMW has used for many years. Heck it's in my 4 cylinder 2.3 litre 1988 M3 which has a stock 4.10 ratio. Higher numerical ratios like 4.27, 4.45 and higher are available. Anywhere from the high 2s to mid 5s has been produced. There is also a lighter duty version with a smaller ring gear which is physically lighter overall. Quaifes and custom conventional LSD units are available too, of the shelf. The new E46 M3 high tech viscous LSD drops right into the piece.

Part of why the rear end is stronger is the case. The output bearings can't move backwards very easily as you can see from this PIC. That is part of what is happening with the S2000 case... the bearing caps are overloaded and cannot keep things in line. They move under load and then stuff no longer lines up the way it should = very bad. Then things wear and break. How do you take apart the thing if it has such a case? Well the output bearing are retained by removeable holders retained by 6 bolts apiece..you can see this in the PIC. When they are removed, the big stuff can then be pulled out the rear of the case. The output shafts simply pull out of their splines by hand and there are several styles - which may help for custom stuff. the halfshafts are no known for clicking either.



Two single mount rear cover styles, late and early..late is the fancier larger one:



Back side of the rear covers:



Rear cover mount attached to diff and unibody frame on an E30 M3...(there is also a dual rear mount version with LH and RHS mounts from the larger cars):



Rear subframe and suspension...you can see that the diff mounts to the subframe with four bolts on it's top side...and the rear cover mounts to the unibody:



Here's a rear view of the rear subframe and so forth:



The rear cover sticks down into the underbody airflow for cooling but is still higher than the lowest part of the exhaust:




They are very strong diffs that can take torquey 6 cylinder engines in heavy vehicles. Nearly 4000 pounds in some cases. At a guess the BMW diffs are likely 20-30 pounds heavier than the s2K diff. They pretty much run forever in E30 M3s.

Rick, I know that you do not care for German iron for some reason, but at least this post shows what others do to keep rear ends together.

HTH, Stan

RT

[QUOTE]Originally posted by E30M3
[B]Is the pinion gear weak or could it be housing related...as in the case *moves* under big loads.

E30M3

>>>Stan, Comptech's modified case is using this idea but since the case itself is not very stiff, they utilize a cap over the stock cap to stabilize it. Like you, I believe most all the pinion gear failures are actually the result of too much change in gear mesh geometry due to a weak carrier assembly. BTW, If we use an M3 diff, do we need to run a guibo (sp?)? Don't know if I can do that, if I can't even spell that <<<

Guibo..."gweeebow". The guibo would not have to be used. They mount in between the tranny output flange and the driveshaft input flange. The BMW rear end's input flange is a conventional three eared piece installed with a solid attachment to the driveshaft output flange. But if you could use a guibo, I think it would help even the stock S2000 rear end as they cushion shock loads. I use the guibo from the E39 M5 / E46 M3 on my E30 M3.

A guibo is basically a rubber u-joint that absorbs shock loads and some NVH. Here's a PIC:



Stan

E30M3

>>>Stan, Comptech's modified case is using this idea but since the case itself is not very stiff, they utilize a cap over the stock cap to stabilize it. Like you, I believe most all the pinion gear failures are actually the result of too much change in gear mesh geometry due to a weak carrier assembly. BTW, If we use an M3 diff, do we need to run a guibo (sp?)? Don't know if I can do that, if I can't even spell that <<<

Also...

I thought that Comptech simply tried to brace the existing bearing cap, still mounted from the original two mounting holes in the case. No lateral bracing either. That's why I showed the diff covers with lateral reinforcement beams and cap braces. Cuz on other diffs the Comptech approach did not work out - inadequate! Stronger yes but not bullletproof. The covers I showed earlier for other diffs push against the bearing cap from a piece mounted in the cover which is then attached to the case via a ring of fasteners. The ring gear tries to move away from the pinion gear and out the back of the case. And it also tries to move sideways. Many more and spread out fasteners are involved in holding the deal together in the instance of the special diff cover concept. It works.

Stan