I hear ya. But my new 2002 A4 never had a problem - nor noise. Then when I swapped in a brand new 3.42 - I again went with the factory fluids... and never had any problems nor noises.

Maybe I'm just lucky.

But I learned a long time ago to never "mess with success"... so I (at least right now) see no reason to move away from the factory fluid.

 

Positraction is GM's trademark name for the limited slip differentials built by them and installed on their vehicles. Other companies have used names like "Equa-Lock", or "Dual-Lock", etc. On street driven vehicles all limited slip differentials operate pretty much the same. HTH

 

Thanks again for the responses guys!! Those of you who used either Redline or Royal Purple without the additive, did you experience any noise or chatter after switching from the GM product?

 

Redline + additive - 75-140

Highly recommended, premixed and bought from Phil at DTE

I have a DTE 3.90 diff, so I follow their instructions.

 

I use water & Kool Aid.

The water is for the diff, the Kool Aid is for me.




Sorry for the jackass answer it shows how little I know about these rear ends. This much I do know... if we have clutch driven type "posi-traction" then the additives are a no-no unless the manufacturer calls for it. I don't think we have a clutch type rear end, actually I think our traction control comes from breaking and power mgmt. But I could be wrong about that too. Maybe I should stick to what I'm good at - jackass answers.

 

Limited Slip Differential Clutch Disc Kit, part # 12458083, 2 required

This is the service part number for the clutch pack assemblies we have and the limited slip additive is needed unless the fluid being used already has it mixed in (such as with Red Line, Amsoil, etc) The additive is what keeps it from chattering when going around corners.
HTH

 

I had the differential grinding noise. I took it to the dealership yesterday. They changed the GM fluid and put in the additive and the noise was almost all gone. As soon as I picked up the car, I took it to work (very large parking lot) and did the CF recommended slow figure-eights (forwards and backwards) and now the noise is completely gone.

 

This conflicts with everything I've heard - not to add the additive if using the Redline in rear end. So, now..... do we use it or not. What's the real story on this. Some say, Redline comes with the slip additive, and adding more is not good. Maybe its cuz you've got 3.90's. I wonder if its ok to use this combo in the 3.42 (A4).

 

I ran the redline in my diff with no issues without the GM friction modifier, since the redline I purchased has the friction modifier already added.

After I had the DTE 4.10's put in, my right rear tire would skip on corners and I noticed additional tire wear on the right side. I changed out the fluid again with redline, but added one bottle of the GM friction modifier on top of the additive that comes with the redline. The problem went away and I have no issues now. The reason the DTE's require the extra modifer is due to the clutch packs being tighter.

If you run a stock rear end, you should not have to add any GM friction modifier to the rear, permitting you purchase the gear lube that has the friction modifier already added. I know redline makes some with and some without.

After you change the fluid, go to a parking lot and do a few figure 8's taking the tightest corners possible.

 

On my 97 I changed over to the Redline fluid and never added the friction modifier. Never had a problem. My 03Z has the GM synthetic in since I had a seal on the diff replaced and they refilled with the correct GM fluid. Haven't had any problems with it either. Didn't make a noise when I picked it up from the dealer.

To answer the one question above about TC and Positraction. The Corvette uses both. Limited slip axle with brake and throttle traction control. Best of all possible combinations.
Bill

 

interesting...

 

From what I have seen, every setup/differential is different. After replacing my differential with 4:10s, I had a chatter with Amsol (friction modifier mixed in). I added 2 oz of Amsol friction modifier and the issue immediately went away.

I would suggest adding small incremental amounts of modifier until rear is quiet. Remember...just enough is the right amount.

 

Reason why I said no additive unless specifically called for is the Eaton G-80 clutch diff on my turbo diesel chevy P/U went south. Replacing it was going to add up to some bucks, so I called Eaton spoke with a pretty senior engineer there and asked what aftermarket replacements they make. His response was there is nothing stronger than factory and you can't break the factory one. Are you sitting down, they actually flew out a replacement to my repair guy at no charge in exchange for getting my bag-o-parts back. We got into very lengthy discussions with the stealership where I first left the car who insisted on changing the fluid + additive. Eaton went ballastic on the additive part as it makes their clutch slip. Finally it was resolved there is no GM bulletin calling for additive although it's commonly done.

Sorry for the long tale, only pointing out not all diff's want or need "additives". Granted some do. Just check it out carefully as there are instances where a little additive isn't an extra good measure.

NOW, I'm going back to jackass snide remarks! This serious stuff is draining.

 

why do that ??? your words were informative

 

I have a DTE diff - I do what they tell me.

 

My question ia how do I ge the oil and additive into the diff and trans. 2 different units but closely related. I can't see where a quart bottle is going to fit under the car.

 

Exactly

 

First: No additive is used in the trans. It uses AUTOMATIC TRANSMISSION FLUID ONLY.

Second: Is a quart bottle is the only way to get fluid into either a trans or diff? Try a plunger type gun. It has a hose. It can be used either as a suction or plunger device. Very easy. Available at many different parts houses. Some are metal, some are plastic. Cheap.

 

Check out this web site. Contact Subdriver on the forum to order.

http://www.c66racing-synthetics.com/...ns/G2039PB.htm

 

We've been asked to chime in here to set things straight regarding our differentials and what lubricants to use with them. Please copy-paste-print off or what-ever to keep as a data reference, as we've covered this very same topic with similar answers on this board about 4-5 times in the past now.

Our Stage 2-5 differentials utilize a heavy duty clutch pack design w/ heavy duty clutch pack pre-load springs that are exclusive to our engineering design. Therefore, in order for our differentials to operate properly in a wide variety of performance conditions/applications, we require the use of Redline brand 75w/140 fully synthetic differential lubricant which has approx. 4% of Redline brand fully synthetic limited slip additive already blended in at the Redline Lubricants factory. We add an additional ounce of Redline fully synthetic limited slip additive to each bottle here at DTE for a total blend of 13%, that supports our heavy duty clutch pack design. We carry this blend here..

DO *NOT* use GM L.S.A. additive in *ANY* of our 75w/140 lubricants at all, in any capacity what-so-ever. That was fine with the old 75w/90 we used to use, but *NOT* for the new 75w/140 blend. If you choose to do this, we can assure you with 100% certainty that you *WILL* have clutch pack problems of some sort.....

If you have a stock differential w/ stock clutch packs or our Stage 1 model differential, we recommend the use of the standard 4% blend of Redline brand 75w/140 lubricant and pour in stright from the bottle. We also carry this blend here..


Thanks folks.


Best Regards,
DTE