ClevelandTim

Guys,

First time changing diff fluid on my 2000. I drained the old oil, added the little bottle of GM friction modifier and then added my new Valvoline 'high performance' diff oil. Then I noticed it was marked 'limited slip' on the bottle, so I'm assuming it also has the friction modifier in it as well. Question is, will too much of the stuff hurt the differential or will I be ok? In other words can my diff overdose on the stuff? If so I'll just drain it and do over.

feeder82

Too much will make it act like a open diff, the clutches will slip. Too little and it will chatter when turning

ClevelandTim

Good to know! So if it was your car would you just dump out the oil and add the stuff I had pictured without the GM friction bottle?

leadfoot4

I believe, if there's too much of the "friction modifier" in the oil, then the differential's clutches will slip too much, and not hook up both rear tires under heavy acceleration.


On the other hand, a number of years ago, we had a Chevy Caprice LTZ in our family fleet. It was basically a "cop car" with a nicer interior, and as such, was equipped with a positraction rear axle. Shortly before we went on a vacation, I gave the car a maintenance "once over", including replacing the diff oil. I used, I seem to recall, Valvoline gear oil that was labeled for use in limited slip differentials. It did NOT have enough friction modifier, and the rear end was NOT happy. Problem for me, was this "situation" didn't appear for several days, and by that time, we were several hundred miles from home............



EDIT....

OP, in the picture you posted, I don't see that the Valvoline oil pictured, is synthetic gear oil. I do believe that the GM spec for C-5 rear axles is synthetic gear oil. FWIW, I've had RedLine's synthetic gear oil in my 2001 C-5 since 2002.

C5SCCA

How much peace of mind is $15 dollars worth? It may be fine, but you will always wonder. My advice...Drain it and do it right!

QCVette

Exactly the same with my Impala SS. I put Valvoline in that said limited slip and it chattered bad. I added one bottle of the GM additive and that made it work great again.

Good luck.

ClevelandTim

Just out of curiosity, I know that synthetics won't break down as quickly as a conventional oil, but on a light use vehicle (like 3,000 miles a year) is their much of a difference?

Bill Curlee

If it were me,,,,,,,,,,,, I would DRAIN and refill with just the GL-5 lube. Take her out in an empty lot and doo a LOT of figure 8 turns. IF,,,,, you ever feel it CHATTER when you do a very tight left or right turn, ADD a LITTLE more limited slip additive.

You can always add a little more limited slip additive. Its expensive to take it out!

YES, it can cause the clutches to NOT function and glaze over.

Bill

ArtGle

When I did my transmission back in December, the dealership parts guys spoke with their 'Corvette Tech' for me about this subject.
He told them, and they sold me a second small bottle of the additive to put in.
He said it was 'better for the posi trac..
This time around, I'm going with just one bottle.
All factory fluids in the differential every time.

The Wrench

I didn't check to confirm, but I seem to remember that the required amount for my 2000 diff was 1/2 of the bottle of GM additive??????
I could be wrong......

That being said, when I had my diff rebuilt last year I put in the Valvolene LS with no additional additive and she's perfect; no chatter and dead-straight pulls when the tires spin.

But, yeah, get it right; oil and changing it are cheap and easy, diffs are a bear to pull out, and a ton of $$$ to repair.

DG

ArtGle

Gentlemen, here is a photo of my factory Service Manual about rear axle fluids

Bill Curlee

Art

GM uses a lube without the modifier. That is why they add the bottle of modifier.

The GL-5 has its own modifier already in it

Bill

k24556

Amazon sells the correct fluid with the correct amount of friction modifier:

ACDelco 10-4034 Dexron LS 75W-90 Gear Oil - 32 oz

somewhere under $18/qt.

reactor2

I added the little GM bottle to my rear end along with Royal Purple differential fluid that already had it. I did that several years ago, I don't notice a difference at all. Both tires spin when it loses traction.

v8srfun

To much friction modifier will cause the diff to act tighter so you may get wheel hop on tight corners. The friction modifier increases friction on the clutches not decreases like the others were saying.

leadfoot4

Nope...........

v8srfun

You may want to do some research

leadfoot4

I did, FIRST HAND. Re-read post #4.............

Bill Curlee

Without friction modifier added to gear oil for use in a limited slip clutch disk differential, the clutches will grab/pop/bind. The situation will be noticed when you do tight turn.

The modifier allows the clutches to slip in a smooth fashion in a controlled amount. TOO much is bad and not enough is also bad.

To properly make the clutches work when you add new oil, you should do some very tight figure eight turn in a safe place to burnish in the new oil/LS fluid and make sure the clutches are happy. You can always add a bit more LS fluid.

I never add the whole bottle to my differential if I use lube that doesn’t have the LS Additive already in it. I put 3/4 of the load in and then see how the clutches work.


Man,, that modifire stuff STINKS!

leadfoot4

OH YEAH!



Smells like "high octane" cat p**s........