Hi guys,
5 years ago, i filled my 4-speed Muncie with GM Synchromesh fluid, based on recommendation from this board at that time.
I'm going to replace my axle seals as one has started a slow leak, so i'm going to change the fluid while i'm in there.
I called my local Pontiac/GMC dealership, and asked their Parts department if they had GM Synchromesh,
and their answer was: "no, we don't have that stuff"
o_O
WTH?
Have they phased it out in favor of something else/better?

What is the current opinion? What should i put in there?
20w-50? Hypoid gear oil? Captain Morgan? Guacamole?
Advice appreciated, y'all.

i put fully synthetic 5w30 in my isuzu 5spd tranny.

Pennzoil makes Synchromesh fluid. It can be found at any Autozone, Advance or other parts stores. It is compatible with the GM Synchromesh so you can mix them if needed. However, I believe the 4spd should use 5w30. I could be wrong, might have to look up where I read that.

[This message has been edited by topher_time (edited 03-24-2008).]

Several years ago GM issued a TSB changing the recommended fluid for ALL manual transmissions (to that point, anyway) to Synchromesh.

thanks guys,
i'll try Penzoil's Synchromesh fluid when i do the drain and refill.

digital brownies for everyone! : )

I bought 2 liters of the synchromesh 2 weeks ago at my GM dealer .

[This message has been edited by Robert 2 (edited 03-24-2008).]

I've put about 200,000 mile on M-17's using Mobil One 5w-30 full synthetic. You can feel the power difference and shifts are great.

quote Originally posted by Robert 2: I bought 2 liters of the synchromesh 2 weeks ago at my GM dealer .

I've found that if you just give them the part number, it takes the "idiot" out of the equation.

I was using 5w30 synthetic and I was having my synchros stick. So I put in Synchromesh and it behaved like a whole new tranny.

Arn

I'm using Red Line Oil's manual transmission fluid. It's meant for race applications, so shifting is a bit notchy when it's cold, but once it warms up it's very nice.

quote Originally posted by ryan.hess: I've found that if you just give them the part number, it takes the "idiot" out of the equation.

Mean if you give them the number they find it right away?????

I use on all 4 and 5 speed tranny service, Royal Purple synthetic manual tranny fluid..

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12345349 I think is the part Number for GM ...........from memory. Anyone?? I bought 3 quarts last week from a local parts store for 9.50 each, the dealership waned 20.00 Each......

[This message has been edited by Gto1966 (edited 03-25-2008).]

quote Originally posted by Gto1966: 12345349 I think is the part Number for GM ...........from memory. Anyone?? I bought 3 quarts last week from a local parts store for 9.50 each, the dealership waned 20.00 Each......

Thats the part number. I just bought 3 quarts from the local chevy dealer. It was only about $8 each.