You could be correct, but the word "Synchromesh" reffers to a manual
transmission, not an automatic.
The owners manual would say exactly which lubricant to use, but the I
assume the poster does not have it.
Wrong!....it's been a long time since
any manual transmission in a Chevy
truck used diff fluid. If you think about
it long enough, your own answer provides
the clue as to why it's not necessary.
Engine oil, and auto trans oil were used
on a regular basis in manual transmissions.
ATF is still used in some manual transmissions.
"Diff fluid"?????? All the manual transmissions I've come across used
90 wt gear oil (or a lighter or heavier grade depending on physical size
and climatic temperature) -- smells like camphor. Using engine oil in a
transmission can cause problems because it's formulated differently than
gear oil-- more detergents and less anti-frothing agents.
But then again if your tranny is made out of some esoteric
expensium/unobtainium alloy, that's totally different.
Yes, you're right. The 4 or 5 trucks I own (IHC 2T, Ford 1 1/2T, Chevy
1T and Chevy dump truck) all have Josephson junction tunneling
transmissions equipped with hyperbaric solid state control and
ferro-fluid bearings. If you want to count the ones in the busses a
friend of mine works on, the number decreases by at least another 50.
With my 3/4 T pickup, I've gone in excess of 300,000 miles using 90 wt
gear oil in an NP 540 -- the model from the 60s for 1 1/2 - 2 ton
trucks, not the puny new version for leetle tiny geeps and Toy-otas.
At any rate, using engine oil in a gearbox of any kind isn't a good idea
because it isn't formulated for that kind of service (unless of course
it's all you've got and you are out in the middle of the desert late on
Sunday night). In some cases mixing lubrcants can lead to a loss of
lubrication altogether. I know someone who once added journal oil to a
Mack Lanova diesel engine, which tore up the rod bearings instantly.
With 2 cycle diesel locomotive engines (EMD), you use one formulation of
/diesel engine/ lube oil (not gasoline engine oil--sorry forget the API
numbers). For 4 cycle (GE) you use a different formulation, or there
will be /serious problems/. It's the same with gear oil and engine oil.
Ask any lubircation specialist, and I don't mean some gear head at your
local OHV shop.
Some gm standard tranny's ,heavy duty 5sp in a 1 ton with a cast iron
housing, need special synthetic gearoil because of their synchro's. Multi
disc instead of brass cone's. If u use 80W90 your tranny won't last long.
Gm, Castrol and Amsoil are the only companies that make the right oil.
Castrol Syntorque, I don't know the GM and Amsoil part #'s
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