I know this subject has been talked about in a few other threads, but they didn't seem to have a definitive answer. Are 75W-90 GL-5 gear oils (like Redline 75W90) okay to use for the rear diff?

Also, is there a way to drain the rear diff oil? I can't seem to find a drain plug?

Thanks in advance

 

Drain plug is on the bottom near the back of the rear diff. I think someone said it's 24mm. I just used a 15/16" socket on mine. Same thing I used for the transfer and tranny drain plugs. The rear diff fill plug is larger than the front ones (which are 17mm) and ended up using the same 15/16" socket as the drain plug.

There is a sticker on the rear diff that says something like "specified LSD oil only." The manual specifies some Mitsubishi gear oil, with no indication of GL rating. I just threw in some Redline Lightweight Shockproof. I did this on Sunday, no problems yet... knock on wood.

 

You need some type of LSD additive if you are not putting in the factory oil. All LSD rears need an additive.

 

timzcat: Redline claims that all of their synthetic gear oils have their LSD additive, except for the 75W90NS. The Shockproof stuff also says it's fine for regular diffs, LSDs, lockers, and transmissions.

So maybe the label on the rear diff is just there to make sure you're aware it's an LSD and not an open diff? Not so that you have to use the oil specified in the manual (cuz I didn't, heh).

 

Wouldn't that be all clutch type LSD's need lsd addative??

 

Just FYI, the lightweight shockproof did start to give me a chattering/stuttering rear diff. I replace it with some Amsoil Series 2000 75W90, drove the car in about 10 figure-8's, and the chattering went away.

I confirmed this with a tech from RedLine. The shockproof doesn't have enough (any?) additive to break the clutches loose in low-speed, tight turn kind of situations. It's designed primarily for racing, where that probably won't be happening anyways.

So I guess the statement on their website about all their fluids having the LSD additive applied only to their normal synthetic gear lubes and not the shockproof synthetic gear lube.

 

I put Red Lne 75W90 in the rear/front diff and MT 90 in the Transaxel. 7K with several road course events and no problems. It does seem to improve the shifting a bit.

 

can i ask why people are changing the fluids sooo soon? sorry i am not knowledgible in this stuff

 

heshamnaim: My car had almost 10k miles on it when I did the change. It had seen 5 AutoX and one AutoX practice day with about 20-30 runs. I felt that it was time to change the fluids, even if I wasn't at the recommended service interval yet. It's cheap insurance against premature failure.

Also, the first change is pretty important because the tranny/diffs have been going through break-in. So there should be more particles in the fluid or trapped by the magnetic drain plugs. Sure enough, my magnetic plugs were heavily covered in filings of various sizes that made a nice black sludge on a rag. Now that the fluid is changed any particles the magnet may have missed are probably gone, and the magnet is clean and can pick up any new crap.

 

thanks for the info....i have 4k on my car...no autox's though....but i do drive crazy.....i think when i put her away for the winter i will do it

 

MT-90 is, if memory serves, a GL-4, not GL-5. The 75W90NS is a GL-5.

By the way, be careful of oils like Mobil 1 gear lube in the transaxle. Some gear oils are corrosive to "yellow metals" ... such as brass synchros.

For a (really long) discussion, see:

http://www.ferrarichat.com/discus/me...20/250478.html

http://www.ferrarichat.com/discus/me...12/285744.html

 

Yes it is a GL4, as recommended by Mitsubishi, BTW these are also the recommended lubricants for this car from Red Line

Manual transaxle Gear oil API classification GL-4 SAE 75W-85W or 75W-90