2001 ws6 m6 & rear diff question

[cfm56]

want to change the tranny oil this week (around 50k on the clock), what brand should i use for dexron III oil that is readily available at the local auto part store?

on the rear diff, it seems as though 75w90 is the weight to go with in the rear diff. 2 qts? also which brand is recommended? do i need additive on my rear diff?

that are the normal tranny & rear diff oil servicing intervals?


its a 2001 transam ws6 m6 tranny, stock except 4 inch tips, eibach pro springs and a k&n filter

thanks for all your input

[SajoR]

When me and my brother rebuilt my t56 tranny, I used the Valvoline MAX-Life Dexron III...Dexron III is usually the most recommended. I've heard Syncromesh can be used as well for high-temp applications such as drag racing or hot climates.

And yes, 75w90 is the way to go in the rear diff. And you're supposed to add GM additive for the limited slip differential, which you probably more than likely have. It's a 4 oz bottle you can buy from the dealership. Some gear oils already come with a synthetic additive (such as Amsoil and Lucas) and don't necessarily need it but I went safe route and bought regular gear oil and the additive from my local GM dealer. Also bought the rear differential cover gasket as well as some RTV silicone sealant and brake cleaner to help clean the diff cover once it was off. You'll only need 2 quarts, but it won't take all 2 quarts, maybe about 1 1/2 to 1 3/4 quarts.

I just did mine not too long ago (took me about 30 minutes or so) and had to lower the rear anti-sway bar to access the bottom 3 bolts (13mm all around). Brake cleaner helped out a lot when it came to cleaning the diff cover and a putty knife to clean up all the old gasket from the diff.

[cfm56]

so do i need to remove the cover on the rear diff to service the oil? or is there the typical drain hole on the bottom and a servicing port on the top/side? (i havent jacked it up yet)

thanks

[Cutlass]

you gotta pull the cover off

[Black 98 formula ws6]

I used royal purple 75-140 awesome, you can really tell the differnce in free ness.

[cfm56]

thanks. Also, is there a standard factory recommended servicing interval for the tran & diff?

[Smokaholik]

You only need the GM additive if you have an Auburn LSD not a Torsen LSD.

[CompSyn]

Yes, your owners manual will say to use 75W-90, but it's too thin and could cause differential noises; at least it has in some LS1 powered cars. If it's mostly a performance street car, go with 75W-110. If it see lots of track time, go with 75W-140.

CompSyn