Limited slip lube question

[SKFengineer]

Long story short... 1993 GMC C1500 with a 10 bolt limited slip rear. Had the rear rebuilt at 185,000 miles due to a bearing failure. Installed new limited slip unit, gears and bearings at that time. Drove the truck for 10,000 miles with no noises or other issues and then changed the diff oil this summer, at that time added one bottle of GM limited slip additive and the required amount of diff fluid. About a week later got the low speed rubbing in the rear when making turns that comes from the limited slip unit clutches grabbing. As a result I drained and refilled the diff fluid with two bottles of GM additive and the problem is still there. Since the additive is not cheap I'm just dealing rubbing noise now until I do some research but I was wondering what are the fine folks of this forum are using in their limited slip diff's.

Thanks

 

[19trax95]

Is it a factor unit?

If it's the g80 you put in there, then that's a locking diff and does not take any additives.

Gm never put a limited slip in their trucks. Only the g80 which is a locker.

Now you can have a g80 in a car and that's a limited slip.

So if you replaced it with a exact factory match unit, then it's a locking diff.

If it's a different type then you'd need to look up that specific unit and see what it takes.

 

[SKFengineer]

It's aftermarket... I believe similar to what my camaro has... The truck had one leg stock. I've talked to the shop that built the rear and then just said the GM diff additive and gear oil, he was very clear only the GM additive.

 

[aaronb]

I used the Red line limited slip additive in my 14 bolt with an auburn limited slip. I ended up using 12 oz to get the chatter to go away. I would try adding another bottle to see if that helps.

 

[SKFengineer]

Okay I checked this morning and this is a Auburn unit in my 10 bolt. Any idea what the total volume of gear oil is needed for the 14 bolt you have? My 10 bolt seems to use about 2 1/2 quarts. Just trying to figure out what ratio of additive to oil you needed. Also do you remember what gear oil viscosity you used in your rear?

 

[aaronb]

Auburn said 3 oz per quart. I have an after market diff cover on my 14 bolt. It takes almost 4 quarts of gear oil.
I would add another 3 oz of additive.

 

[aaronb]

I used 80w90 gear oil

 

[SKFengineer]

So I'm going to be changing the fluid in the rear again shortly so I'll be able to report on the results but one last question. Most shops in this area claim the GM additive is the best and only one I should consider. I see above you've had good results with the redline additive and I believe your results so I want to consider trying that additive however I was wondering if any one else has some experience with these additives? Good / bad, brand whatever, just trying to understand I the products on the market.

 

[aaronb]

I tried the gm additive that came with the auburn unit, and still had the chatter.I read up on additives and found the Red line by searching for my issue.the red line is a little pricey. I paid $7 per 3 Oz.it's the friction modifier you want. Read up on it.it's good stuff.