merlot566jka just put some in his 96 LT4 C4 ZF transmission. said it shifts smoother. i have to drain my getrag since i need to replace an axle. need to refill it with something... i was thinking RP since i heard a good review on it.

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First LX9 Fiero GT, 1987 | My Fiero Fuel Economy | MPG Display for OBD I
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I wouldn't use anything other than syncromesh. I tried redline MT fluid once a long time ago and it was worse than the 5W30 that was originally prescribed for GM FWD MT's. Once I learned that syncromesh was the fluid specified in later service bulletins I switched to that and have never turned back.

Royal Purple might be the next greatest thing but if your not already running syncromesh any decent MT fluid might be better than what might currently be in your transmission.

it has syncromesh in it now... that im gonna hafta drain

In that case, throw in some royal purple and write a review. I'm going to be rebuilding a trans soon and need to know which fluid to put in it

I have Royal Purple Syncromesh in my 85 SE with a 88 cradle and the 3.4 DOHC and a FWD Getrag. The tranny shifts like butter.

Joe Sokol

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85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)

quote Originally posted by Fieroking: I have Royal Purple Syncromesh in my 85 SE with a 88 cradle and the 3.4 DOHC and a FWD Getrag. The tranny shifts like butter. Joe Sokol

Just a slight correction or clarification. Royal Purple's product is Synchromax not Synchromesh.

I looked through their product info and found no indication that it meets any GM specifications for MT fluid. In their cross reference guide however it does state that GM transmissions that specify Synchromesh fluid should use their Synchromax fluid.

Just to throw something else in the mix...If you want a higher quality fluid which meets GM specifications and even qualifies for use under the GM 12345349 Synchromesh part number I would consider Amsoil.

[This message has been edited by Jefrysuko (edited 07-07-2010).]

I'm using Amsoil Synchromesh. Works just fine.

quote Originally posted by americasfuture2k: merlot566jka just put some in his 96 LT4 C4 ZF transmission. said it shifts smoother. i have to drain my getrag since i need to replace an axle. need to refill it with something... i was thinking RP since i heard a good review on it.

that stuff is awesome for the getrag and isuzu's. for the muncie, i still feel that 5w30 works best in the 4 speed.

quote Royal Purple: GM all models (Synchromesh) arrow Synchromax

You can get the Penzoil Syncomesh found at AutoZone. Supposedly its the same as GM sells. I've heard that they make it for GM. Its like $6 a Qt. I use it in my car, shifts great.

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1987 SE / Fastback - 3500T / 4T60e / OBD1 / broken
Projects: 5-speed swap / retune

Synchromesh is the BEST thing you can have in your manual trans.
the reason is: Synchromesh is basicly a synthtetic oil, with no detergents and added anti-foam

the orginal spec'd fluid was straight oil.
this gets gummy, and makes for sticky shifting when the oil breaks down (and it will)
switch to a synthetic oil, and it smooths out
now - switch to a synthetic with low detergents, to not eat thru seals and anti-foam to keep it from frothing up as it gets "geared" - and it gets even better.

so - yes - from just plain old oil - Royal Purple is a step up. from synchromesh - RP it is a step down

Royal Purple is made for a different environment. absolutely it will work, and work better than plain old oil. but - synchromesh is made speciicly to be a gear oil.

quote Originally posted by americasfuture2k: it has syncromesh in it now... that im gonna hafta drain

You could drain it into an empty jug, and pour it back in. This is assuming it's still relatively clean.

quote Originally posted by Pyrthian: Royal Purple is made for a different environment. absolutely it will work, and work better than plain old oil. but - synchromesh is made speciicly to be a gear oil.

I'm going to challenge your statement. We are talking about using Royal Purple Synchromax which is purposefully formulated for manual transmissions much like Synchromesh. Take a look at the link I provided in a previous post for more info.

I would not have a problem with your statement if we were talking about using Royal Purple 5W30 but that is not the case.

quote Originally posted by Jefrysuko: I'm going to challenge your statement. We are talking about using Royal Purple Synchromax which is purposefully formulated for manual transmissions much like Synchromesh. Take a look at the link I provided in a previous post for more info. I would not have a problem with your statement if we were talking about using Royal Purple 5W30 but that is not the case.

didnt see that in the opening post, and assumed he was speaking of the 5w-30 synth oil.

quote Originally posted by 87_special: You can get the Penzoil Syncomesh found at AutoZone. Supposedly its the same as GM sells. I've heard that they make it for GM. Its like $6 a Qt. I use it in my car, shifts great.

Same here. If the RP cost more than 20% I wouldn't bother as I doubt the difference would be that big. If less then I would try it just to see.

I don't like the idea of using motor oil in a transmission. It's regular oil which means it too will need to be changed every 3k. Possibly more often since it's always being geared. More of a breakdown. In a motor, it's mostly being sloshed from the crank and through the oil journeys across the valvetrain. Not as crazy of an environment as being meshed through multiple gears. My brother changed his ZF oil with RP syncromax. Now that's made to be in a constantly crazy environment.

Another vote for Amsoil synthetic synchromesh.

quote Originally posted by americasfuture2k: I don't like the idea of using motor oil in a transmission. It's regular oil which means it too will need to be changed every 3k. Possibly more often since it's always being geared. More of a breakdown. In a motor, it's mostly being sloshed from the crank and through the oil journeys across the valvetrain. Not as crazy of an environment as being meshed through multiple gears. My brother changed his ZF oil with RP syncromax. Now that's made to be in a constantly crazy environment.

The engine is a far "rougher" environment than the transmission. It's way hotter, plus there's contamination from combustion by-products that don't exist in a transmission.

Any time I've changed the oil on a manual transmission, even after 10+ years of service, the oil still looked clear, and not blackened at all, like engine oil.

3000 mile transmission oil changes with engine oil is way excessive.

Good points, sir. Good points.