Manual tranny & synthetic ATF?

[SteveR]

I just put a T56 manual 6-speed transmission in my car (uses ATF instead of gear oil). A lot of the guys who run these say that they think synthetic causes problems with the synchros. Right now I'm running Mobil 1 ATF and everything seems fine, but I'd like for it to stay that way. Does anyone have any experience with this? Any comments?

Some people complain of grinding after going to synthetic ATF...which might make sense since the synchros probably wouldn't work as well with a more slippery lube. Is there really that much difference?

 

[Patman]

When I put Mobil 1 ATF in my T56 that was in my 98 Formula, the grinding started (on a cold 1-2 shift at higher rpms) The T56 does not like synthetic fluids, stick with Dexron III.

 

[Dominic]

My T5 really enjoys the Durablend ATF I'm running in it. Its so much smoother shifting than the crud that came in it from factory!

 

[jason07-1zzfe]

I would (and do) use Red Line MTL. It will shift like hot butter at ALL temps and provide more protection than ATF, especially dino ATF. My car specs 80w GL4. Red Line says MTL can also replace ATF, while providing greater protection.

I think they spec ATF because of the thinner viscosity with better cold shifting. Most gear oils don't come that thin. But MTL is proper visc.
Red Line MTL:

If trans specs 90w or xw-90 oil then you need Red Line MT90.

 

[Soma07]

I ran Mobil I ATF in my T56 for a nearly 40k miles with no problems. Recently I switched to Honda ATF as suggested by some guys on the F-body boards but I didnt notice any difference between it and the M1.

Maybe in colder climates you would see more of a difference?

 

[Judd]

I've tried stock, Mobil 1 ATF,and now I'm on GM's Synchromesh in my T56. So far I like the Synchromesh the best. I got the tip from a ford buddy. When I asked my dealer about it, they flat said "BAD" don't use anything but DexIII. Then I called GM customer service and they said it was fine. Tried it and I like it better than the Mobil 1 ATF. Just my two cents.