wicks

Noise is getting a bit different - now I've got crunching noise going forward at full lock left or right. Different sound/feel than in reverse, which is the diff kind of "graunching" while being forced to slip while turning in reverse.

Maybe it's not my diff? CV joints going?

How do I inspect the diff, must I remove it, or there is a cover plate that would allow me to diagnose?

I read that a worn CV joint will make the half shaft feel loose while wiggling with both hands. Maybe I should just replace the half shafts?

bweSteve

still feels / sounds like a trans oil issue to me. I know you changed it,... but again slip additives maybe? (or do they call them friction modifier additives?)

Vince964T

Agree with ppl here, start with the diff oil.

Engine temp is normal. Especially if it was not to warm outside and you were not standing still to much in traffic or red lights.

You can run 150mph or more for ever, well the time it takes to run out of gas, so may be not that long and the engine temp will stay around that level actually.

urquattro20Vt

Yeah the faster you drive the cooler they run!

Wicks - I’m no expert on differentials but you might want to have an expert take a look. Or do a quick test first. Jack up the rear of the car and, in neutral, rotate a wheel? What does the opposite wheel do?

i just learned that my limited slip is totally shot. Not sure your mileage - I’m at 106K. So winter is here and the big project will be to have the diff rebuilt, new clutch and new coil overs.

Brandon
’91 Turbo

wicks

Here are a couple of videos showing noise/action of the half shafts. Both wheels turn forward/back together when turning either wheel on jacks. Both half shafts slide in and out freely, neither appear to have any play in splines. The left half shaft has some clunk at the ends - I've not taken apart these hubs before so don't know what's against what at the moment. Pushing shaft in toward the diff, something seems to "tap in" a bit at diff. Then pulling back out toward hub, something seems to "tap in" there as well. Not sure if either end showing some noise/tapping in could indicate a problem.

Sound on:

From right (overall play etc): https://imgur.com/zVsivtV

Left (something "tapping in" at ends): https://imgur.com/a/hmRaJac

wicks

Anyone take a minute to opine?

Igooz

Wicks,
I am not an expert, but I have listened but do not know root cause, however this is what I know:

I daily drove a 1991 964 Turbo from 1993-2001 and the LSD never made any noise. In 1997 I had the opportunity to buy a 1994 964 Turbo and during the test drive I noticed the LSD noises, chatter, etc. at low speed turns, reverse turns, etc. I did not buy that car as my wife poopoo'd on it that it smelled like mildew...Fast forward 18 years later and I bought a ~1994 Turbo, and it makes the same LSD chatters, noises when turning as the only other one I had test driven many years ago.

wicks

Yes indeed I had the normal noise klunk behavior, but then, SOMETHING CHANGED.

"as if I were tapping the throttle a bit on an off while decelerating in a turn. Almost like a surge problem on an MFI car. Seems like it would come from an uneven or high idle, but neither of those problems exist"

Because something changed, I know there is a problem. Decelerating in a straight line, no problem. As soon as I am in a turn, the car surges slightly. Perhaps the diff is "winding up" somehow and then releasing, causing this problem. I've never worked on a diff before, so this is an area I don't really understand.

The car has run on several spirited drives like this now, and it seems to be staying the same, but I don't want to break the diff (or a half shaft) while driving, so I'd rather figure out what's wrong and fix it. Current thinking is that because the problem only happens while cornering, it must be the diff. Perhaps I should just pull it and rebuild/replace.

wicks

Diff seems to be getting klunkier and chunkier, so zeroing in on that. Will the diff just keep getting worse, or will it actually break/fail and I'll be stuck?

cobalt

The diff makes noise and a little clunky when it is working. Failure is the loss of friction material and will no longer lock acting like an open diff. When that happens it will no longer make noise or do much of anything. If it is getting clunkier or noisier I would say it is time to open up the trans and inspect the LSD. Although I am assuming you have inspected all your wheel bearings and CV joints? I wouldn't put it off if you feel it is getting worse.

wicks

This turned out to be the inner CV splines. Shredded on both sides. Maybe caused by diff acting up. Not wanting to do this job I had Bill Manuel the classic dept. guy at Rusnak replace the inner CVs and repack outers and re-boot all 4, and rebuild the diff at same time with the new carbon plates. Works smooth as silk now. Bill is very experienced and very good, if anyone is looking for a posh mechanic solution in the LA area.

urquattro20Vt

Glad you found the issue. And thanks for keeping us posted.

I’m curious to hear more about the rebuilt diff - using the new carbon plates - is this new factory parts? Or?

My car is going in next week for a big job - including a new Guard GT2 Club LSD (and KW V3 coilovers and a clutch). Matt at Guard no longer rebuilds the OE diffs - just sells new LSDs - which are supposed to be awesome. But curious about your solution.

Glad to hear you’re back on the road

Brandon
’91 Turbo

wicks

Yes genuine parts all. Only listing of the disc with a picture - https://www.rosepassion.com/en/parts...43-2109-149125

Car doesn't klunk backing up anymore either. Think these new pressure discs just work far better than the original materials.