# How much rear-end whine is normal?



## Bradd55 (Oct 22, 2012)

A little info on the car, 2004 GTO 5.7L 6spd(105k miles). I took this car for a test drive at the local dealership, i noticed on light acceleration in between 40 and about 55 mph there is a slight wine from the rear-end. With the radio off and passenger silent, windows up, you can barely hear it. I'm not sure when the last time they changed fluids, but as with any car a fresh fluid change can some times make the whine stop. Some people have told me that a little rear-end whine, while not necessarily "bad", is "ok". What is your input on the issue? 

Last thing i want to do is buy this car for $11,000 then have the rear-end go out on me. I'm not familiar with LS1's or their drive-trains outside of just knowing specs about it. Let me know your thoughts, thanks everybody!


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## GTO JUDGE (May 14, 2005)

My rear end was replaced under warranty. I have 0 noise. Some report a slight whine. 

Everyone's idea of slight is different.

Have this seller drain the fluid and replace with new synthetic with the correct amount of F1 friction modifier. Some gear oil has the PROPER FM in it. It has to be GM approved F.M.

The car has to be driven a bit for the fluid to work its way around. Depending on what "sight" is it may the way it will be. 

If it were me I'd insist on the seller having a former Pontiac dealer check it out before purchasing it. You are probably OK on this but as with any performance car I suggest a DECENT extended warranty especially with the high miles on this.


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## jpalamar (Jul 22, 2008)

Bradd55 said:


> A little info on the car, 2004 GTO 5.7L 6spd(105k miles). I took this car for a test drive at the local dealership, i noticed on light acceleration in between 40 and about 55 mph there is a slight wine from the rear-end. With the radio off and passenger silent, windows up, you can barely hear it. I'm not sure when the last time they changed fluids, but as with any car a fresh fluid change can some times make the whine stop. Some people have told me that a little rear-end whine, while not necessarily "bad", is "ok". What is your input on the issue?
> 
> Last thing i want to do is buy this car for $11,000 then have the rear-end go out on me. I'm not familiar with LS1's or their drive-trains outside of just knowing specs about it. Let me know your thoughts, thanks everybody!


I'd have the owner change all the fluids before I bought it or I'd ask for $1000 off for the hastle/risk of doing it myself.


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## svede1212 (Nov 1, 2005)

Not a fan of synthetic. The Aussies all recommend dyno and our Dana is an Aussie diff. Whine usually isn't a function of lube but of the gear lash set right anyways. Once it's run it and the gears break in you can't reset it though. 

I'm also not a fan of pre-mixed friction modifier and lube. Because of the non-exact way our cone anti-slips work the modifier amount can be anything from half the "recommended" amount to twice as much. You really need to start low and keep adding until chatter on turns just goes away. I've seen cars with the speced amount do one wheel peel-outs because they have too much.


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## GTO JUDGE (May 14, 2005)

Synthetic was installed in mine at the dealership= 0 noise. GM friction modifier installed.

I prefer not to install premixed FM either. 

At last I heard GM FM is no longer available I could have sworn I read this. Type F 1 was used. Make sure the FM you use is GM approved.


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## Gotagoat (Jan 6, 2006)

Svede and Judge, which lube specifically do each of you have in your car? I'm about to have mine changed and am interested in your choices.


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## GTO JUDGE (May 14, 2005)

Gotagoat said:


> Svede and Judge, which lube specifically do each of you have in your car? I'm about to have mine changed and am interested in your choices.


I used what the dealer installed. 
SAE 75W-140 GL-5 Synthetic Gear
Oil (GM Part No. 89021809). 1 oz.
(25 ml) of Limited-Slip Differential
Friction Modifier 7098
(GM Part No. 89021958

On my own I'd use a quality alternative with the proper viscosity gear oil. 

I recall reading someplace this FM is no longer available but don't quote me. Call a GM service center and check to make sure.


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## svede1212 (Nov 1, 2005)

Gotagoat said:


> Svede and Judge, which lube specifically do each of you have in your car? I'm about to have mine changed and am interested in your choices.


Torco RGO 85w140 with their FM modifier added as I noted above. Dealers are about as clueless about these cars as a high school shop class.


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## EagleGoat (Jun 6, 2012)

I thought the consensus recommendation was the F type modifier for our cars? Something about the cones?


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## GTO JUDGE (May 14, 2005)

I'm lucky, my dealer is very good. Helps when my service writer has a GTO. They know I am on my game with this car... they will install aftermarket parts for me too. They've done it. It pays to be on a good rapport with the dealer.


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## svede1212 (Nov 1, 2005)

EagleGoat said:


> I thought the consensus recommendation was the F type modifier for our cars? Something about the cones?


Type-F, FM (F modifier) same thing. The wrong one is type-G


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