R200 Rotation Preload after LSD Carrier Swap

[Nigel]

Does anyone bother to check this after swapping in an LSD carrier? I just transfered an LSD carrier from a 3.7 to a 3.54 diff. I tried the side shims that came with the 3.54, but the backlash was .011, so then I put in the shims that came with the 3.7 and that dropped the backlash to 0.005. Both diffs were between .008 and .009 before. With the 3.54 shims, the shims slid in easily. With the 3.7 shims, I had to give the last shim in a few taps to get it to seat. But when I measured the rotating torque on the pinion, it was only about 3 inlbs. The spec calls for somethinig like 10 to 20 inlbs. No side seals or stub axles installed yet though. I've read all of the threads I can find on swapping an LSD carrier, but no one mentions checking the preload. They only ever talk about measuring the backlash. Should I worry about this?

 

Also, I did the math in the FSM for determining the side shims needed, assuming that the different bearings won't make a significat difference. According to the numbers, I should only need about a 0.05mm thicker shim on the left side to get the right backlash. But the left side shims from the 3.7 are actually about 0.3mm thicker. Still, like I said, this gave me a backlash of 0.005, which is within spec. The 3.7 right side shim is not quite proportionately smaller, so I get a bit more bearing preload, but judging by the input torque, it's not excessive. I'm going to try marking the teeth to see if the wear pattern is ok.

Any thoughts or suggestions?

 

Nigel

[JMortensen]

One benefit of carrier bearing preload is that it prevents the ring gear from torquing away from the pinion. IMO our R200s don't have enough. Most diffs require that you beat the carrier into the housing with a dead blow hammer. My R200 carrier just fell into the housing. That said, I didn't mess with it because problems with the gears are so rare, but it is different than most others.

 

The best way to test pinion bearing preload is with the carrier out. A new seal will dramatically increase pinion bearing preload, and IIRC the FSM even has a spec for with a seal and without a seal. Checking it with the LSD installed means that you're adding in a whole bunch of other stuff, gear friction etc, so I'd test pinion preload by itself and I wouldn't bother testing it at all with the carrier installed.

 

I would try and get it shimmed back closer to what it was previously. If you have the diff at .008 and ran it that way for 100K miles, then you move it to .005, you might find that you get a gear whine out of it, because they're now wearing in a different spot. FWIW, the few that I've done were all .005 or thereabouts.

[Nigel]

Thanks for the reply Jon.

 

I don't have the FSM in front of me, but it does state to check the pinion preload before disassembling anything and again at the very end of assembly. It does also mention checking it when setting up just the pinion, which is probably what you're thinking of.

 

I've run the 3.7 with the LSD for years, and I could really feel that 8 to 9 thou backlash. Other people who drove my car even commented on it. I hoped to tighten it up a bit, but maybe going to 0.005" is too much? I guess it's a gamble if I throw it in the car like that though.

 

Nigel

[JMortensen]

You're probably not feeling backlash.

http://forums.hybridz.org/topic/105207-the-dreaded-diff-clunk/

[Nigel]

You're probably not feeling backlash.

http://forums.hybridz.org/topic/105207-the-dreaded-diff-clunk/

 

I did read that. But thanks for the reminder not to get too focused on the diff. However, I have an RT front mount with a poly bushing, and poly bushings in the mustasche bar, so the diff itself isn't going anywhere. I have CV axles, and I've had three difference transmissions in the car, and two different driveshafts, none with any discernable play. It definitely sounds and feels like the diff teeth clacking together. The poly bushings don't help to dampen it much. Regardless, it's not a huge concern, but I thought perhaps I could remedy it somewhat by getting the backlash back in spec.

 

It turns out that there's a driveline shop down the street from work that a coworker knows the owner of, so I'm going to bring the diff there for final setup. With 20+ year old parts, experience starts to count more than specifications and precise measurements.

 

Nigel

[Nigel]

Update:

 

I did take the diff to the driveline shop. They checked it over and made a small adjustment to the side shims. The backlash is now down to 0.004", which is slightly tighter than minimum spec. This made me a bit nervous, but I finally got to drive the car yesterday and so far, it appears the shop knew what they were doing. The diff 'feels' great. There's even less vibration than the old 3.7. No unusual noises either, at least not up to 75mph. The clunking that I was experiencing before when getting on and off the throttle is now gone too. I was going to say it was definitely the backlash in the old diff that was causing that. However, it just occurred to me that there's a possibility that the bolt attaching the diff bushing to the Ron Tyler bracket may have been slightly loose.

 

Unfortunately, I wasn't able to check the preload again. All the torque wrenches we have at work were sent out for calibration.

 

I'm going on a long drive this coming weekend. Fingers crossed that this differential is in the car for life.

 

Nigel

[RebekahsZ]

With the way we have to grind down the poly bushing on the RTmount to conform to the snout of the diff, it really weakens the poly. I have torn the bolt out thru the poly such that it rubs on the case of the diff metal to metal. I think I have torn the second one, but it is still restraining the diff fine, I think I hear the metal to metal click. I'm hoping it will hold together till winter when I hope to modify the rt mount to use some other bushing. I'm dropping the clutch at 4000 with slicks.

[Nigel]

My mount is fine, but I think the bolt that is included with it too long. On mine it was boring right into the polly, and felt like it was hitting something. I shortened it by at least 1/4"

[RebekahsZ]

Hmmm, I may need to rethink the problem. I will look at the bolt length on mine.