best fluid for T56 6-speed, and what is the Dexron3 requirement?

[Ron-Indy]

Be careful what fluids you try as some will ruin the syncro / blocker ring friction material which is either carbon or fiber depending on year of manufacture. Mobil 1 synthetic ATF as an example.

Tremac factory fills all T-56's with Dexron III except the Dodge Viper which is factory filled with Castrol Syntorq sythentic. It's a considerable heavier weight oil than dexron and is available at Dodge and GM dealers under various part numbers.

I use Syntorq in my T-56 and am happy with it, both in shift quaility and quietness.

 

[1 FMF]

For the Tremec T56 6-speeds found in the Camaro's, Firebird's and Corvettes, the manuals say use Dexron3 atf, even though it's a manual transmission. I don't know about you all, but mine shifts like crap and it doesn't shift at all when it's cold. I'm considering using one of the following: amsoil synthetic atf, redline hi-temp atf or redline MTL.

I've used Redline D4atf in my 99 camaro 6-speed. It shifted great when it was cold, but during the summer when the car was hot it felt like the d4atf was too thin. When shifting when it was hot the transmission would sort of bang when you shifted into the next gear, like the syncros weren't getting the gears to the same rpm before engaging. Don't get me wrong, the thing shifted good and all and I never had any problems, but I honestly think the d4atf was, too thin for a lack of a better word. I was reading the redline website and either their hi-temp atf or MTL look ideal. I'm a little hesitant about amsoil because it has the same viscosity of the d4atf at 100C, about 7.5. The redline hi-temp atf and MTL are 10.0 at 100C, and even though their viscosities at lower temps are higher than the d4atf, I would hope they would give at least some better shiftability during cold weather than the factory fill dexron3 atf.
The only thing I'm worried about is the Dexron3 requirement stated in the manual. Do I abolutely need to use dexron IIE or dexronIII atf? The redline hitemp atf meets dexron3, but the MTL according to the redline literature seems better suited but it doesn't meet dexron3. After all the T56 = manual syncromesh tranny = MTL = manual trans. lube. So why use an atf in a manual tranny. Would there be any compatibility issues using the MTL even though it's not dexron3 compliant? And what is the definition behind dexron3 does anybody know? And has anybody used either amsoil or redline mtl in both cold and hot weather with success?

 

[Patman]

When I had my 6 speed 98 Formula, I put in Mobil 1 ATF and soon after I had syncro problems. The 1-2 shift would grind when cold.

I've heard many LS1 owners comment that the Honda fluid works well in the T56. Same with Redline's MTL.

 

[Dr. T]

I too have a 6 speed that specs out Dextron II/e. The reason is because it's a tranny fluid that's readily available. This means there should be NO problems running M-1 as it is Dextron II rated. I have used it with great results. Now running Castrol Syntec Dextron II/III...also with great results.

Haven't used Redline, so I can't comment directly. They say to run MTL in manual trannies. Guys that I have talked to have had great results with their dextron II atf....otherwise, I had a friend that used their MTL in his 1994 Mustang and it destroyed the tranny synchros...

 

[Bror Jace]

"I had a friend that used their MTL in his 1994 Mustang and it destroyed the tranny synchros..."

You'll have to color me skeptical. One Miata driver here tried MTL when his car called for a 90 weight oil and I believe him when he said the shift quality was never the same.

But I have a hard time believing that MTL destroyed a Mustang's synchros unless it was a totally wrong weight. Was he already having trouble and then swuitched to MTL? Was it his aggressive driving and/or missed shifts?

--- Bror Jace

 

[Michael SR]

GM Synchromesh works awesome in T-56s. (and T-5s, and TR-3550s, and ZF6s, and...)

-michael

 

[Judd]

Ditto on what Michael said. I have a 2000 Firebird, I have the same shifting problems. It's about the only manual I've had that I can't powershift well. It really perturbes me to no end. One week after getting the car, I went to rip off a shift and weeeeiiig-missed it! Thought-hmmm??? I'll try that again. Same thing! Dern, won't try that again till I put in a Pro5.0 shifter. Installed the shifter-same thing, missed shifts.
I then changed to Mobil 1 ATF at around 5K miles, did not like it at all. Changed back to Dextron after about a 1k miles. A friend that is into Fords told me about GM's Syncromesh and I tried it-I like it. Still can not powershift it though. Like I said, I have a 2000 and it has a crappy slave/ master cylinder that I'm pretty sure is causing my shifting problems.
Funny thing about the Syncromesh. My dealership's mechanic flat told me "Nothing but Dextron will work, anything else will mess it up.". I asked about the Syncromesh and he said the same thing. I then called GM customer relations/questions department and asked if Syncromesh would work and they said "Yes, it is actually recommended". Dunno what to think, I just know I like it the best between regular Dextron and Mobil 1.

 

[vettenuts]

I put Amsoil in my Vette transmission. While it shifted better then stock, I still notice some "grind", expecially when cold. It goes away after the car runs a while though. I am curious about this GM sychromesh fluid, what is it and is it synthetic?

 

[Judd]

I don't really remember if it was synthetic or not. You can get it from any dealership, the dealership I got it from had it in stock.
The stuff looks different than ATF, it's a brownish amber color if I rember right. It also seemed a bit thicker than ATF.
Like I said, a friend that's into Fords said it was recommeded to him buy a aftermarket builder of T5 and TKO trannys. They said it was the best stuff they had found. I don't really know about that as I would think that Redline would be good also. I just know it was better than M1 Synthetic for me.

 

[RobZ71LM7]

I had some occasional problems with M1 ATF in my '94 T56. I switched to regular Pennzoil Dexron III and it works perfectly.

 

[vette#one]

I just bought GM Synchromesh. I have heard from other people that it works well in their Corvette 6 speeds. I did use Red Line MTL also. I was pleased with the difference that it made in shifting.Then I had the transmission rebuilt. Right now I have Royal Purple in it. Seems O.K. I'll let everyone know if there is a difference.