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Discussion Starter #1
Ok, I haven't been on here in a year because some senior members didn't like my opinions on Amsoil, but I'm back to just say that I've learned some new stuff about GTO diffs that may come in handy to those who are considering fluid services. My diff started grinding and clunking a few weeks ago and, even though I'd changed the fluids and had no problems until now, I researched again on gear oils. Anyway, I took my car to the dealer and had them swap out my Amsoil 75w140 with AcDelco 75w90 LS Series gear oil. Friction modifier is already premixed, however they still have a friction modifier sold separately for the trucks and SUV models. It's a type "F" apparently and is fine in the GM performance models as well. It fixed my problem completely. It also cured the noises that I figured could be bad bearings, bushings, half shafts, etc. Really nice considering I'd already budgeted for my entire tax refund being burnt in 2 days :willy:

Reason for the fluid change (courtesy of the Corvette Tech, not my "opinion") was that older model differentials (01-07) had metal/metal clutches which were prone to wear and make noise quicker without a "right" friction additive. GTOs are filled with a 140winter viscosity from the factory, and the friction modifier becomes useless as the oil wears slightly but retains its hot flow properties. Nowadays, the clutches have been redesigned (including new GTO rears). The good news is that if your differential noise is only due to worn fluid, then the new GM recommended fluid will fix the issue and the differential will be fine.

Advice? Buy the fluid at GM Parts Direct: Your direct source for Genuine GM Parts cause its only $12 per quart there as opposed to $22 at the dealer (PN 88862624). I hope this info is helpful to anyone who's become worried or unsure about their cars!
 

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Holy crap, I didn't think of shipping. Well I guess it's cheaper in person then. Good lookin out. Can't believe it's that pricey though. :cheers
 

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Yeah I noticed that after I posted. Been off the forum for a while but remember a lot of people making new threads about the same noises. Just excited I don't need a new diff
Under warranty, the changing out of the fluids was the first step in seeing if the noises stopped, to many me included it didn't. Then the rear was changed at the recommendation of the service manager.

After my new rear was replaced, shortly after I was getting the growling. They changed it all out added new FM and after a day of driving it, it stopped. The rear is quiet. Its good you didn't need a new rear. Lots of guys new to this car have no clue on this issue and it was a common one.
 

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Yeah I was crossing my fingers as I watched the tech drain the fluid. Came out mildly cloudy but no metal or metallic color. BIG sigh of relief. I was actually surprised, as I've been using the old spec fluid since the car was born. How much did the new diff run you, if you don't mind my asking?
 

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I had a similar problem with an '02 AWD Chevy Venture Van. It started making a howling/grinding noise when making sharp turns just after the warranty expired! They quoted me a fix of $5500. One service manager told me of a TSB put out by GM about changing the versi-track fluid with a new type they had developed. $50 per quart! He said to change the fluid, take it to a parking lot and crank the wheel as hard as I could and drive it around in a circle for 5 min. I did and within 1 min. the noise stopped. Never had any more trouble with it after that. Lots of other problems with that POS, but at least I didn't have to spend 5K on it. I got on line and read a lot of people with the Chevy Venture and Olds Bravada having this problem. They had a class action suit against GM over it in Canada. Should have been a recall.
 

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Yeah I was crossing my fingers as I watched the tech drain the fluid. Came out mildly cloudy but no metal or metallic color. BIG sigh of relief. I was actually surprised, as I've been using the old spec fluid since the car was born. How much did the new diff run you, if you don't mind my asking?
Was replaced under warranty. They did not rebuild them. The entire unit came as one part number and is a Dana rear. Dana made good on them.

Now with the warranties past I would think rebuilding them would be cheaper than replacing.
 

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I have an issue similar to this. Under moderately light acceleration I can feel a popping through my arm rest. It is really not audible. It usually pops 3 to 5 times on then stops as I get to moving past 5 to 15 mph. It will do it in first or second gear. I have an A4 and it changes to second really fast under light acceleration which I am sure is normal. I am getting concerned about this! Rear CV's? Or is it related to this post? 06 A4
 

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I have an issue similar to this. Under moderately light acceleration I can feel a popping through my arm rest. It is really not audible. It usually pops 3 to 5 times on then stops as I get to moving past 5 to 15 mph. It will do it in first or second gear. I have an A4 and it changes to second really fast under light acceleration which I am sure is normal. I am getting concerned about this! Rear CV's? Or is it related to this post? 06 A4
I'd say replace the diff fluid.
 
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