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Good afternoon everyone


Im trying to figure out what sort of manual transmission fluid I can put into my 1985 720 Z24. From what I've gathered, the following are viable;


All GL-4 BTW, and this is for the climate of British Columbia, Canada


- Redline MT90 75w90

- ACDelco Synchromesh with Friction modifiers (Can't seem to find any locally)

-Sta-Lube 85w90 (No one carries this it seems)


Are there other options? 2 of the 3 on this list im having a hell of a time tracking down and MT99 75w90 seems like it may be too thin on its own.


Some insight is appreciated



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Last time I tried to find the Delco it wasn't available. Try Amazon? US and Can use different GM part numbers. The real stuff is thin and amber/orange color. I asked a GM dealer what the new Corvette was using in the manuals and he said it was a pink colored ATF.


Red Line and Royal Purple and several others are probably the same base stock but with different color additives. It's thin and it works wonders but can leak past the old output seals. Shifts faster, shifts much easier when cold and down shifts way better. It's not cheap though.


Otherwise GL-4 80 or 90w is fine.

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Ended up running MT90 75w90. So far no leaks but have purchased a output shaft seal just in case. I plan to replace it in the near future.


I had another question regarding the transmission.

Mine seems to fight me a little to get into gear. It's not consistent but happens maybe 50% of the time regardless of speed. Is that just a characteristic of this transmission or should I strip it down and inspect?

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Check your hydraulic clutch fluid. Any air trapped in the hydraulics will reduce clutch disengagement preventing the clutch disc from fully disconnecting from the engine. The synchronizer rings are overwhelmed and shifting is harder. Try shifting into reverse, does it grind???  

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