Yeah, but with increased heat you also have better fluid, right? So that should balance out.

Besides, the 'clutch packs' add heat generally in a autocross/roadrace situation. The diffs still fail when you're going straight.

Also, by running lower gears (higher number) you are allevieting some tension from the housing.


All that and they still fail.

The bottom line is that cast iron when designed like ours is, is not the strongest way to go. the one I'm working on will be made out of aluminum and be tons stronger.

 

Slick rick, Keep me updated on your diff project- sound very interesting.

Rev, The 1st torque step is low, 14ft/lbs. this doesn't even come close to seating the bearings. (The service manual states checking turning force here, but there should be none) You spin the pinion to make sure the bearings aren't cocked in the races. then you increase the pinion torque to 95ft/lbs. This seats the front pinion bearing to the crush collar, but does not seat the bearings to the races. You will still be able to pull in and out on the companion flange. After 95 ft/lbs, you increase the torque on the pinion nut untill the pinion bearings are just seated. pull in and out on the companion flange until all movement is gone, but there should be no preload on the bearings. turning force will be 0. The torque to achieve this is around125 ft/lbs. Then, you continue to torque the pinion nut untill a turning torque measurement of 7.8-12.1 in/lbs. You have to have a beam style torque wrench to measure turning force. The wrench will be 1/4 drive to get a scale this low. when measuring you have to take the slack out of the adapters from the wrench to the socket. (nobody makes a 1/4 drive 26mm socket) When increasing the pinion nut torque on theis step go 1 ft/lb at a time. The turning force increases rapidly with pinion nut torque. You should end up with a torque reading in the 130 ft/lb area. Of course after doing all of this, you have to check gear pattern and backlash and adjust pinion depth accordingly. (which means trashing the pinion seal, nut and crush sleeve, pressing the pinion bearing off and swapping shims.) And you get to set pinion turning force all over again. I have a feeling your pinion bearings didn't have enough preload which could have led to your failure.

 

If you have access to a lathe and surface grinder, I'd suggest replacing the crush sleeve with a solid spacer. It will make life easier when setting up a new diff. Turn the spacer out of bar stock, and leave it a few thou longer than the old crush sleeve. Then, when setting the pinion bearing preload, first crank the nut down gently to make sure you left the solid spacer long enough (don't want to crush the sh*t out of the bearings accidentally). Then for subsequent trials, you just just crank the nut down to 100 ft*lb or so and check the preload. Disassemble and put the spacer on the surface grinder and take off a thou or two. Repeat. The same could be accomplished w/o a grinder by leaving the collar a bit short and using shims.

Benefits:
-no seals present when checking preload (more accurate)
-once you have the spacer to the correct length, no need to go through the crushing procedure for each new crush sleeve (parts & time - especially if you need to set pinion depth)
-remove any chance of companion flange nut loosening over time; If the crush sleeve were ever to move/yield a little bit under operation (not sure how this would happen) you loose the clamping force in this "joint" from the torque applied to the nut. I only raise up this last item because loose companion flanges is an issue on 323 GTX's and I used to have one and it's flange did come loose. I caught it before it wrecked the gears, thankfully.

When I did this procedure on my old 323 GTX, I put a dial indicator on the companion flange and pulled it in and out to figure out how much I had to take off the spacer initially to get the bearings close to seating.

HTH,
Steve

 

You could make a solid spacer to replace the crush sleeve, It's a pretty common practice on 8 3/4 Chrysler diff's. You will need to make it smaller than a "crushed" crush sleeve, then adjust pinion turning force with a shim pack. If you know a good machinist, It can be done. The pinion turning force is esentially bearing preload. The shims will most likely have to be made as well. You could try domestic suppliers such as Mark Williams, Strange, Randy's Ring and Pinion. I don't know if there would be enough of a market for them to develop a solid spacer kit, but it wouldn't hurt to ask.

 

[QUOTE]Originally posted by Slows2k
You could make a solid spacer to replace the crush sleeve, It's a pretty common practice on 8 3/4 Chrysler diff's. You will need to make it smaller than a "crushed" crush sleeve, then adjust pinion turning force with a shim pack. If you know a good machinist,

 

You couldn't use the OEM shims because they are radiused on the inner edge to clear the radius on the pinion itself. The shims are also huge, 3.08mm-3.45mm. The are also super expensive for a shim set. I think they retail for around $200 a set.

The crush collar works just fine, It's just a PITA if you have to change your pinion depth, and trash the collar and seal everytime. The pinion nut really is a one use item as well.

 

[QUOTE]Originally posted by im4u2nv81
sorry for imposing as I own an SRT4 but, have any S2k owners considered/performed a rear diff cooler setup?

 

tear down, it may be needing just rebuild of clutch pack as its that type of diff. that's a added benefit of clutch type diffs, other than better traction, as opposed to gear diffs which cause collateral damage to other components, like R and P, housing, when they send a tooth flying.

 

When the clutch packs on a diff go out, it doesn't fail, it just starts working like an open diff. A clutch pack diff is basically no different than an open diff except that it has clutch packs between the side gears and the casing of the differential itself to restrict wheelspin (and a cam to determine how much the side gears will be loaded against the clutches).

 

S2Kophiles,

I'm putting an S2K driveline into a race car and have some observations about the rear halfshafts which may be contributing to the differential failures.

Most drivelines are designed with some wind up somewhere to that shock loads such as clutch drops, or tyres touching down after wheelspins are cushioned. In most modern cars the halfshafts are made relatively thin so they wind up under load. In the S2K the rear halfshafts are huge, almost 2 inches diameter compared to many other cars with more horsepower that have 1 to 1.25 inch halfshafts. Apaft from the sprung clutch centre there is very little spring available in the S2K driveline. The standard S2K halfshafts are so thick I doubt there would be any real wind up in them.

Has anyone tried using thinner custom halfshafts in the S2K? I believe that using them would help reduce the shock loads in the differential and gearbox. I'm using custom halfshafts in my race car of 1" diameter which is the same as we have used previously with a Miata differential and rear hubs. We have run these at over 330hp without any problems with lots of race starts and slicks. ( with a solid clutch centre)

I remember an article on the turbo era F1 cars. They had so much torque that the Williams cars used to wind up the halfshafts a full 360 degrees under power. Amazing.

Speedracer.