Tranny fluid
 

I just had some new fluids put in the DSM (the rear diff, tranny, and xfer case). All the fluids are Castrol Syntec 75w90 (GL5), but now I hear that this could ruin the synchros in my tranny. Anyone have personal experience with this happening or can tell me for sure this is the wrong stuff to put in the transmission?

Re: Tranny fluid
 

GL5 does not belong in DSM transmissions, a GL4 fluid is required. GL5 fluids can eat yellow metals (such as our brass synchros). If I were you I would drain, fill with a cheap generic GL4, drive around for a few times, drain, and refill with some Redline MT-90/MTL. The GL5 75W-90 is the proper fluid in your rear diff.

Re: Tranny fluid
 

Straight from Mobile One:

The GL-5 lubricant has high levels of EP additives which is sulfur and will erode yellow parts found in many transmission such as brass and bronze parts. Therefore Mobil does not recommend our product be used in any transmission using yellow metals under any circumstances.

States right in the owners manual... GL4 for the tranny and GL5 for the diff.

Re: Tranny fluid
 

South Central Imports stocks the MT90 and MTL, going there after work today and getting some cheap GL4 to flush first from the nearby Checker.

3 quarts (2 mt90, 1 mtl) is enough for the tranny/xfer case?

Re: Tranny fluid
 

Yep that is enough to do both. Good idea with the flush! The checkers Ive been to dont carry GL4 so hopefully one by you does.

Re: Tranny fluid
 

I called and they said they did. He listed off a bunch of weights/numbers. He said they had some cheap GL4 75w-90. But that's the stuff I have in there now, so I'm confused.

I had to explain to the guy what gl4 even was. He asked me what part that is for a transmission. Will it say on the bottle if it's gl4 or gl5?

Re: Tranny fluid
 

as weird as it is, some things will be GL5 but say they meet GL4 specs. I don't know if they are talking about lubrication qualities or if they can be used with "yellow" metals.

Re: Tranny fluid
 

You have a GL5 75W-90 in your tranny right now, the generic GL4 75W-90 will be fine to use as your flushing fluid. It will say GL-4 on the bottle.

Re: Tranny fluid
 

3 is all you *should* need, but depending on how you're extracting it from the bottle it wouldn't be a bad idea to pick up a 2nd bottle of MT-90 just in case.

Fill tranny with 1 quart of MT-90, then MTL, and then top off with the 2nd quart of MT-90. Fill xfer case with leftover MT-90.

Re: Tranny fluid
 

The xfer case doesn't have any yellow metals in it does it?

Re: Tranny fluid
 

No I dont think it does, but I would still drain it. Look in the manual to see if the transfer case is GL4 or GL5.