1998 WS6 differential noise question

[SeptemberC]

Good morning everyone, I am new to the LS1 forum. My husband and I have owned our 98 since 2000.
He recently(2 weeks ago) performed the differential service and even now when doing the slow figure 8's he is still getting chatter noise.

He used Lucas Synthetic and Trans X.

Now we are trying to decide where to go and what to do from here. Do we try to add more Trans X? Do we start all over and use NO Trans X? Do we start all over and use Non-Synthetic and OEM additive?

Any opinions would be greatly appreciated. Also, can someone confirm that the 98's have the Auburn differential?

Pictures I attached below are just to show you how well taken care of the car is.

https://photos.app.goo.gl/WiAYbQFSRfDe7NYf7

[SMWS6TA]

Did you add the limited slip additive?

[SeptemberC]

We added TRANS-X POSI-TRAC Limited Slip Gear Oil Additive is designed to quiet chattering differentials and improve gear oil performance. Use with conventional GL-5 or synthetic gear oils.

[SMWS6TA]

what weight of oil did you use?


when he drained it did he see any signs of bearing material or wear?

[SeptemberC]

We used Lucas 75-90 Synthetic. No debris, shavings, or any gear wear at all.

[SMWS6TA]

To answer your question about Auburn differential.

98 came standard with it though it is possible it could have come with the Torsen. Only way to tell is see if it has clutch packs (Auburn) or worm gears (Torsen).


Mine was an Auburn. I now have a 8.8.


Is the noise whine or chatter? Does it increase on decel or acceleration? In turns?

[SeptemberC]

There is a very small amount of whine on acceleration and deceleration at interstate speeds only. The chatter/squeak happens when making slow speed 90 degree turns, figure 8's & complete circles. So basically anytime that one wheel is travelling faster than the other. We have not had the transmission apart only the diff cover off. The gears looked BRAND NEW and we have LOTS of experience with gears. Of course you can't see the clutches. . .

[SMWS6TA]

How many miles?

[SeptemberC]

DAMN LOL ! I knew you were going to eventually ask that question. 103,021 . My husband drove it to work 85 interstate miles everyday. He is an old street / drag racer. He never drove this hard, raced it or abused it. We are old folks and he's torn up and rebuilt enough Camaro's in his youth. It only had 2500 miles on it when we bought it. No one believes that it has that many miles on it when they look at it for any reason. If he could keep this in our livingroom he would have.

[SMWS6TA]

It wouldn't be a bad idea to do the bearings as well as the outer wheel bearings. While miles do grind them down, sitting still for long periods of time dry rots rubber seals and will allow moisture to find it's way in and go to work on them as well.



The clutch packs on the rear are probably due too.

[SeptemberC]

Agreed. Bearings and clutches probably need replaced. However, do you think the current noise issues are due to the tired bearings and clutch plates or a differential fluid viscosity issue?

[TLS_Addict]

If it didn't make noise before and it's making it after the fluid change my money is on the fluid. As said though a rebuild kit isn't a bad idea at 100k miles.

[SMWS6TA]

^^this

[SeptemberC]

Thank you. We are going to do a fluid swap

[pajeff02]

Agree. Swap the fluid and try running the GM Posi additive.

[SeptemberC]

Update: Fluid Swap and GM posi additive done. . . Still same noise but only after driving for 15 minutes or so. Forums are wonderful as a community coming together can offer a combined knowledge base. Having said that we also had a friend come over and drive it to give his 2 cents. This is what we have newly discovered - The noise stops completely if the clutch is pushed in. So, we are driving in a circle or figure 8. . . it starts making the noise, push in on clutch, the noise stops, let clutch back out, noise returns.

So now what is it? and why did it only start after fluid change?

and THANKS AGAIN for all of the responses.

[TLS_Addict]

I can't imagine a rear end makes noise based upon the clutch being engaged or not. Throw out bearing perhaps?

[SeptemberC]

We have come to this conclusion also. The sound must be traveling down the drive shaft. We will keep you posted! Thanks again for the support!

[SMWS6TA]

Throw out bearing or even the pilot bearing. Cheap insurance to change the pilot bearing while there.

But another important question, how old is the clutch? Original?

If so time to look at a replacement, depending on how you abuse it, stock clutches last between 75-120k miles.

You might still have enough clutch material to still get around but you can't be having too much left. Mine lasted till 108k miles when I had to change it.

A drop in stock (well better than stock) is the LS7 clutch kit. For stock motors or even builds up to the 500 ft lb of tq, it is the go to clutch kit.

I used it till I pushed past it's capability when I swapped to a 403ci.

They usually go for around $500-550.

[RHershner]

Clutching it un/loads the drivetrain from the clutch to the wheels, so if it goes away when you push the clutch in that would indicate it is excited only under a load and the problem resides *somewhere* between the clutch and the wheels. Could be spauled bearings or gears, preload or backlash out-of-spec from age/wear/failure; could be in the diff, driveshaft, trans or clutch.

Just because you noticed it after servicing the differential doesn’t mean it wasn’t there before, that’s just when you were intune enough to notice it and now you can’t NOT notice it. Because you noticed it when you serviced the diff, that’s the best place to start. When you open the diff, inspect bearings, clutches and gears for wear and/or damage. Be sure to also pull the axles so you can inspect the outer axle bearings as well. To determine if preload/backlash are a potential problem, inspect the ring and pinion gears for heavy wear; if you can feel an edge with your thumb from wear/non-wear parts of the gear face, that could be a factor.

You *could* rebuild the differential based on mileage, but why would you if there isn’t anything wrong? And if that wasn’t the true issue, you’ll be that much more frustrated.

At this point, we’ve all described a lot of technical things with words that have technical meanings (for instance, noises can be classified as squeaks, rattle, buzz, boom, whoot, groan, croak, grinding, squealing, clunk, bang, snap, etc..) and some customers aren’t familiar with what we mean by each of those noises because they haven’t experienced the different noises and been trained on what they’re called. For me, it has taken 23 (professional) years of wrenching and engineering and its stuff that’s difficult to explain because it really takes experience to identify noises and where they’re coming from. So if it’s out of your skill set to identify the noise and/or the location, there’s no shame in taking it to a trained professional. You’ll likely pay 1.0 hour checkout, but $140(?) could save you from needlessly replacing components you don’t need.

To put it into perspective, when I was wrenching at a dealership, it would cost a customer ~$1,200 to rebuild a posi diff and only 3.5 hours of labor (~$250.. I just dated myself.. haha). So to rebuild the diff, you’re going to be roughly $900 in parts, a lot of beer and cussing and may still need someone to help set preload and backlash (precision measurement equipment needed for that). And then you may find it’s still there if it was, say a driveshaft u-joint. I believe the OEM u-joints are non-greasable and they do tend to squeak/squeal when they dry out and could progress to a vibration, then to a clunk and ultimately to failure if left unattended.


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