Outer Limits 4x4 Board

There are hundred's of threads on what oil to use in what gearbox, t.case, and diff's.

There are equally as many differing opinions, one thread says one thing another threads something contradictory.......

Truck spec's are:

1989 3.5 EFI Manual

LT77S (bigger bearing model?)
Borg Warner Viscous Center diff
Standard front and rear diff's.


For the LT77:

Haynes manual says 20W 50
British forums say ATF
Outers threads seem to point to 75w hypoid gear oil

For the Borg T.Case:

Haynes says 90w oil
Outers says ATF
British forum said ATF


Diffs just plain old 80w 90

From my research so far, i have come up with the conclusion that I'm going to use 75w85 in the LT77 as it will be doing some light duty towing with my trailer and SJ413 on the back, ATF in the T.Case and 80w90 for the Diff's,

Does that sound right??

DieselBoy wrote: From my research so far, i have come up with the conclusion that I'm going to use 75w85 in the LT77 as it will be doing some light duty towing with my trailer and SJ413 on the back, ATF in the T.Case and 80w90 for the Diff's,

Does that sound right??

The only one I might be inclined to disagree on is the gearbox itself... not too sure how the LT77 handles that vs ATF. I know the oil you've chosen is preferable for R380s, and I don't think there is any funny inside an LT77 that would make it cause issues (unlike the transfer cases on a 4 speed!). Never tried it in my LT77 though.

The factory specification is ATF. Using anything heavier make cold shifting poor and can damage the POS oil pump...

These days, there are a lot of low viscosity manual transmission fluids and some of them are good for these boxes. They provide better synchro action and protect the gears more than ATF.

Here is a list I compiled, http://www.members.shaw.ca/jbarge/MTF.htm

VMX80 is available at any shop in Oz, IIRC. You should be able to track down some of the synthetic choices as well like the Castrol Syntrans Max.

I see Castrol Aurtralia recommends Syntrans 75W/85 (for LT77S Discos). A bit heavy but it should be good assuming you are not in a colder area of the country.

The t. case is the same thing. Factory says ATF. An MTF would probably be a little better. Too heavy and the viscous coupling would be unhappy. BTW, these cases seem to die fairly regularly....