Syn gear lube or syn ATF?

[joe]

Hi all,
In my newly found 83 Chero I'm swapping the axle juice to syn gear lube.
I'm also considering going syn in the trans/x-case but this is where I need help...
The T-5 manual tranny and 208 x-case presently live on ATF. Should I go with syn gear lube in these also or go with syn ATF or just keep using conventional ATF?
Any ideas here are welcome...thanks.

[reddog]

Shouldn't the T5 have gear oil in it?? I would just go syn on whatever the recommended fluid is on both. I would bet the 208 uses trans fluid but I am not sure.

Kerry

[joe]

They both use ATF Kerry. The early(80 and 81) TSM's say gear lube but AMC soon found out that doesn't work well and since went to ATF. I've got a T5 in a CJ8 and tried running gear lube in it once. Shifted poor even where I live in the fall. In a place like MN I doubt I'd have been able to shift it at all in the winter.
I'm sure syn ATF will work just fine in both the T5 and 208 but I'm hoping the gods are smiling and say I can use syn gear oil in those too so I just have to get one 5 gal bucket of juice for the trans/x-case/and axles. Don't hurt to hope huh? smile.gif

[Stolen76]

Need to stick with ATF in gear case, can't tell you for sure on the t-case. If you are comfortable with the seals and gaskets go for synthetic. The worst part about a syn swap is the stuff tends to run by older seals.

[Jeepzilla]

Hmmmmm, my 81 TSM says the model 208 transfer case gets 10W-30 motor oil. Gotta think that lubricating issues are all the same though: slipperyness, viscosity, resistence to viscosity breakdown, and antifoaming properties. We have had the motor oil debate. Stands to reason that since automatic trannies work on the principle of hydraulic pressure that they hold hydraulic fluid, which all ATF is anyhow. It lubes too. Synthetic anything is slipperier, stays slippery at high temps and does not lose viscosity at high temps. In an engine the real issue is viscosity breakdown on account of the type of bearings used. The crank and rods literally float on a cushion of oil. You gotta float those parts and the discussions come around what does that the best under all conditions.

Manual tansmissions use roller bearings. Their main need is to be slippery at all times, don't need to float. That's why there is no oil pump or oil pressure guage in a manual tranny. The italics in the manual specify do not use lubes that contain lead, chlorine or sulphur. This sounds like pollution control but chorine and sulphur can also turn into acid (HCl and H2SO4) and lead builds up on parts just like it used to in engines. The reason they specify SAE90 oil is to preserve the slipperyness and viscosity at high temps. Synthetics do that well and did not exist in 1981.

I guess all this means is that you can use what you want as long as you satisfy the above conditions. To absolutely KNOW that they are satisfied is to go by the book. Now, a Harley Davidson V-twin uses roller bearings on its crankpin. They say NEVER use synthetic oil because it is SO slippery that the roller bearings don't roll at high RPMs, they skid. The skid not only ruins the friction-reducing purpose of the bearing race, but also make flat spots on the rollers themselves. Not good in the long run.

I dunno where this leaves you, but FWIW...

[ November 30, 2002, 05:45 AM: Message edited by: Jeepzilla ]

[joe]

Originally posted by Jeepzilla:
Hmmmmm, my 81 TSM says the model 208 transfer case gets 10W-30 motor oil. That's correct jeepzilla...i had gear lube on my little brain but yup it took motor lube in the early years. The later ones that called for ATF were identical though, same bearings etc just a fluid change.
To be on the safe side since both boxes call for ATF I'll just try syn ATF rather than syn gear lube.
I'm not too worried about any new leaks. Both these gear boxes are tight. It's been my experience running syn motor oil anyway that if it's not leaking before the swap it won't leak after. I started running Mobil 1 in a 70 F250 360 motor in about 1995 that didn't leak then and 5 or 6 years later when I sold it, it still didn't leak....<shrug>.
Thanks for the reply.