I just picked up a 3.42 10-bolt posi disk brake rear from a junkyard this past weekend. Since I don't know its original origins I figure I might as well service it while its still out of the car.

1st question: What weight gear oil do I need to use, assuming I use regular gear oil and not synthetic? what if I did use synthetic what weight should I use?

2nd question: How many bottles of fluid does it take to fill the rear? I do know I also have to add that limited slip additive as well.

3rd question: What should I look for when I take off the cover as far as the gears go to make sure they are in good shape besides broken teeth?

Anything else I should know by all means I am all ears.

Thanks for your time

 

http://www.bfranker.badz28.com/fbody/lubeoil.htm

Should give you what you need to know.

 

Great site!!! I just used it about 2 weeks ago. It is really a breeze!! Just watch your knuckles on the gear teeth and such and you'll be okay.

 

Thanks guys that helped out a lot.

I do have a question though whats the deal with all the different weights for the oil? Whats the best weight to use for a daily driver?

Thanks

 

I use 5w-30, yours probably calls for the same thing in the owners manual.

I'm sure someone can post a link to a Oil reference page but the numbers have to do with the "thickness" of the oil.

That's a really simplified explaination but you want to stick with what the manufacter recommends for the most part.

 

You're referring to the gear oil, I assume -
I use GM (75w90 if I remember correctly) and a bottle of GM limited slip fluid - don't forget to pick that up too.

 

Thanks for the replies guys. It just really confused me in the parts store. They had so many different weights available.

The synthetics seemed to be like 90W140 is that ok to use or should I just stick with the regular oil at 75W90.

I am just lost as to how I am supposed to figure out which one is the ideal weight.

Thanks again for the replies

 

I've used exactly what was listed in Brent's website as well, that'd be Mobil 1 75w90 synthetic gear oil. 2 qts, plus the limited slip fluid from the dealer. It's 4 oz and costs about $7 or so. Sounds expensive, but the carrier costs a good deal more.. make sure you get some, it's cheap insurance.

 

The correct oil for the rear end is 80W90 GL-5. That is, if you're using conventional oil. Some have claimed problems using synthetic in the rear diff. I'm happy with how mine is holding up, so when I changed the oil this weekend, I installed the conventional oil and the additive, which is what I've always used. "If it ain't broke, don't fix it"

Dan

 

I use mobil 1 75w90 gear oil(takes two bottles) and a bottle of GM limited slip additive. Great stuff! I have not been able to find a gasket for the rear end, so make sure you have some cleaner/degreaser, rags, and some RTV to make your own gasket when re-installing the rear cover.

 

Has anyone used the Royal Purple, just curious cuz Im about to change mine soon.

 

My brother uses royal purple and is obsessed with it. I don't see all the fuss.