Differential slipping issues

[xcastaway]

I recently attempted to solve the issues with my differential slipping by replacing the lsd clutches, which did not fix it. There is a very noticeable slipping internally in the diff in the lower gears under very little acceleration, nowhere near enough to spin the tires. I had some problems getting it back together, as it is a two man job to get it torqued properly, and I only had me. But I've put 1k miles on it since then with no apparent problems due to coming up 5 lbs short on torque, no odd sounds or vibrations or indications that I messed up gear lash or added any new issues, but I'm not comfortable with it, and will fix that part when I go back in there to try and fix this slipping problem.

However, I have no idea what could cause this slipping, as I know diddly about LSDs. My only other thought would be to replace the 2 belleville spring washers that are on either side of the clutches, but I'm not sure what they do or if they are related to the problem or not. I need to make about a thousand mile trip this month, and I don't want to risk having the old girl towed home that far.

Can anyone who does know something about LSDs give me a clue as to what else might be causing it to slip so I can fix this once and for all? Or, as an alternative, does anyone from the PNW have a good, 188mm medium case 3.23 diff, lsd or open, for a 93-95 manual 525i with Getrag lying around that I could buy? There are several 3 series in the local boneyards that I could buy the diff from, but I doubt my abilities to replace the input flanges without causing problems, and evidently non e34 diffs use different input flanges.

I still haven't done the breakaway torque test that Moroza suggested, as it starts pouring every time I decide to check it. I'll go out and get wet if it will help solve this!

My initial thread from swapping the diff clutches.

https://www.bimmerforums.com/forum/s...t=clusterbleep

[moroza]

What oil are you using?

[xcastaway]

Redline 75w90 with the additives for limited slip. For the life of me I cannot figure out what could be slipping in there. It feels like a badly slipping clutch, only from the diff.


OOps.

[xcastaway]

Redline 75w90 with the additives for limited slip. For the life of me I cannot figure out what could be slipping in there, which complicates fixing it. It feels like a badly slipping clutch, only from the diff., which was why I replaced the clutches in there. The ring and pinion, the bearings, and all the fiddly bits in there appear to me to be fine. I'd be happy to replace the $8 ea. spring washers, or even the $50 ea. big spring washers, if I could be at least pretty sure I was fixing the right things.
Thanks.

[demetk]

Did you measure the breakaway torque on it?

[xcastaway]

In a break with tradition, it actually stopped raining when I went out to test it. If I did it correctly, the breakaway point is at 40 foot lbs, give or take a pound or two. 41.5 is as close as I can measure it. I did the passenger side, if that makes a difference. I also measured using a lug nut, with wheel still on, rather than properly centered, with the correct tool. I'm guessing, as I do not know what the breakaway should be, that it should be higher than that. The question now becomes, what does that tell me re: fixing this thing? I've wracked my brain trying to figure out what parts could conceivably affect this, and the only ones that come to mind are the 2 little and 2 big conical belleville washers. I am totally open for suggestions, if any other culprits could be involved.

Thanks!

Edit: I found those washers at a much lower price and ordered all 4. I'll replace them either way when they get here, since the diff has to come out and apart anyway. I've recruited a neighbor to help with the 2 man parts of this.

[demetk]

I think spec is 35-50 ft-lbs so it looks good to me. Post what it is after you replace the washers.

[xcastaway]

I haven't managed to find the breakaway spec for it with the Google, but I did blunder across something that led me to believe I'm on the right track with replacing those washers while shopping for them. They are going to take a week to get here, I'll stick them right in, and fingers crossed, the slipping issue will be resolved. I'll re check the breakaway then and post the results of both.

Thanks.

[xcastaway]

Aww, crap. The fine folks who sold me those parts do not have them and cannot get them. No idea why they thought it was a good idea to sell them to me, given those facts, but I'm back to the drawing board. Looks like I'll have to have them shipped from Europe now, when I needed them yesterday. Sigh.

[xcastaway]

My parts finally showed up from Germany, and I dropped the diff and installed everything and stuck it all back together, with the correct length bolts, properly torqued this time. Even with two of us, holding the ring carrier and getting those 8 bolts to 25 ft/lbs was a struggle. I feel better about only getting them to 20 by myself the first time. It would probably have been fine, all the bolts stayed snug as it was, but I wasn't comfortable with it. And since there was still a bit of slippage back there I had to cure anyway, I had a second shot at getting it right. I only have about 20 miles on it since the repair, but there is no slipping, no odd noises or feelings, so hopeful I managed a repair that I'd thought beyond my abilities.

I went out and tried the breakaway test prior to posting this, and my back convinced me that in excess of 120 ft/lbs was close enough. I went with the big belleville washers from Racing Diffs, who I bought the clutches and dog ear plates from. They are supposed to be stronger bits than ZF used, so higher breakaway than stock was expected. I need to put a few hundred miles on her to make sure everything is kosher before going for my tour of Oregon, camping in the Touring, but I'm pretty confident I got it right.

Since my late April trip is now hopefully going to finally happen in late July, I worked on my sunroof for several days while waiting for parts. My a/c didn't work when I bought her, and is still a few steps down the priority list, so airflow became important. After cleaning all the rtv I sealed it off with when it refused to open a while back, and twisting my sunroof wrench into knots trying to open it. I finally had to resort to drastic measures to manage it. Applying any more force to an allen socket was going to break the gears in the motor, so I had to bend the front inner panel up out of it's track, which didn't go well. It broke one of the thankfully replaceable front tabs off the panel, but also broke the end off the irreplaceable plastic guide for the drivers front of the front outer panel. Sigh. But there was no way it was ever going to open again without using firm pressure on the back of the front outer panel. The motors weren't strong enough to do it on their own. Even after lubing the heck out of everything, it moves very slowly. Both panels open fine now, as long as I give it help to start with, and it will close it I get outside and keep the panel even as it runs thru it's closing routine. Finding and replacing those parts I'll worry about later.

I hated adding another repair to my finally fairly short list of things I need to attend to. After 11 years, I'm down to the a/c and cruise control, neither of which has worked since I bought it, an abs issue which I believe is either air still in the abs unit, or an issue with the unit, and figuring out how to get my horn to work with no slip ring. The brakes work okay, but the pedal is inconsistent as to how far into it's travel you need to press, and the abs light comes on after most hard brake applications. Calipers and all brake hoses have been replaced, and I have vacuum bled them dozens of times, including after going out and locking up the brakes on gravel roads trying to get all the air out of the system. I put an M sport steering wheel from an e39 in to replace the stock minivan wheel, and it doesn't appear that there are any slip rings that will work. I don't care about getting the airbag or signal cancelling, or any of the multi function buttons to work, but there are times I could use a horn. Any helpful hints anyone might have regarding any of those issues would be welcomed.

And finally, as I was under the car wrenching, I started marveling at just how little of the car that I bought 11 years ago is still there. In the rear, only the subframe, trailing arms, the 2 round diff mount bushings, and brake backing plates are original. In the front, the main cross member, strut towers, steering box, and sway bars came with it. All the bushings and other bits have been replaced, sometimes twice. Of the cooling system, only the heater core remains. The steering box is still there, but every other bit is replaced. Only the motor, other than most of its gaskets, hasn't been messed with. It's crazy, how much maintenance these things require! But even with purchase price, a parts car, and pretty much most of a new car worth of parts, she still hasn't cost much over $5k, if you don't count any of my labor. And its pretty much a new car, so much better than the rolling wreck I picked up way back when. I'm going to try to get most of these last things done before the rains return.


edit: My giubo/guibo, which looked fine from the outside, was totally destroyed in the middle, and contributed greatly to the slipping I was feeling. There was still slipping issues from the diff after replacing it. All seems good now.