What is Synchromesh Trans Fluid ?

cruise down to the parts store and find a can with that name. check the label and make sure it says GM bla bla bla # equivalent.

Usually called gear oil or gear lubricant, either 80/90 or 85/140 with a GL-5 rating.

Should be available in any car parts store fairly cheap.

Tom I dont think it takes heavy oil, hard shifting would occur on cold mornings. I think it takes a 30 weight oil or automatic trans. fluid.

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.

AT fluid in a manual trans!!?? Hypoid grease!

~KJ/TLGM

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.

Ian

Only work on "long time since" trucks - my apologies.

~KJ/TLGM

"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.

Pete

Gear oil, 80/90 weight gear, diff fluid...it's all the same thing, just different words.

Boy, hate to break it you Pete, you haven't come across many manual transmissions lately, have you?

Ian

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.

Pete

It is probably 10W30 (or similar) w/ an additive pack.. Check with GM though.

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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.

What year is your S-10? I will look up the right AMSOIL fluid for you transmission.

Bruce Wappman Wappman Motorsports

motorsports.wappman.com

1.877.290.0135