Changing Diff fluid

[Yakisoba]

Well, it's about that time. Need to change the diff fluid. Is there a special limited slip additive from GM that I need to get? I was told of such by a fellow Vette person at a track day recently, but I had not heard of it. Thanks.
--Yak

[jub jub]

Originally Posted by Yakisoba

Well, it's about that time. Need to change the diff fluid. Is there a special limited slip additive from GM that I need to get? I was told of such by a fellow Vette person at a track day recently, but I had not heard of it. Thanks.
--Yak

Yes, just go to the parts counter and tell him you want some of that "limited slip additive". It's in a 4 ounce bottle.

[Terry S]

Others will not agree, but from all I have read you can't get a better gear lube for the diff. than the regular synthetic that GM sells. And yes use the additive unless GM has come out with gear lube that contains the additive. If so hopefully the bottle will say so.

[Subdriver]

Originally Posted by Yakisoba

Well, it's about that time. Need to change the diff fluid. Is there a special limited slip additive from GM that I need to get? I was told of such by a fellow Vette person at a track day recently, but I had not heard of it. Thanks.
--Yak

Yak,
I think we beat this to death on the other forum, but for those reading this thread that haven't seen that one...

The diff does require a friction modifier, but... many good fluids such as the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 you are using come with the friction modifier pre-mixed in. Redline 75w90 (as opposed to the 75w90NS) also comes with modifier in it.

If the fluid comes with the friction modifier in it, don't add what amount to an extra bottle unless your diff chatters. Mine has never chattered, so I've never needed to add any modifier to mine.

P.S. I appreciate the support.

[injuner]

Also, I would suggest that if you are trying it yourself to order a quality fluid pump like the AMSOIL hand pump (can be found at subdriver's store). It screws right into a number of different oil containers and pumps fluid out and up a hose into your diff.. It sure beats a turkey baster!

[Subdriver]

Originally Posted by injuner

It sure beats a turkey baster!

That it does, thanks for the mention.

Here is the pump he is talking about:
AMSOIL Hand Pump

I ought to take mine to the store and see exactly what bottles it fits on as I'm not really sure and I've been asked that question via PMs many times now.

For those that want a cheaper alternative, most auto parts stores sell lower quality versions of this pump. I used one before switching to AMSOIL. I also didn't worry about whether it screwed onto the bottle or not. I just stuck the hose down into the bottle, held the pump with one hand and pumped with the other. But, I like the AMSOIL pump better than those as its volume per pump is much higher than those I've bought in the store. Probably not an issue if you change your fluid once every couple of years, but I change my diff and tranny fluids many times a season.

[Nithros]

Originally Posted by injuner

Also, I would suggest that if you are trying it yourself to order a quality fluid pump like the AMSOIL hand pump (can be found at subdriver's store). It screws right into a number of different oil containers and pumps fluid out and up a hose into your diff.. It sure beats a turkey baster!

I didn't have a pump but I did have a piece of clear hose that I ran from the fill out through the wheel and then into the bottom of a funnel where I could pour the fluid in easily.