Synthetic ATF or Synthetic Synchromesh in T45 Trans?

[paradigm]

I've been doing some searching on the forums, and cannot seem to find a conclusive answer as to what the best transmission fluid is for the T-45 trans (Specifically for the 99-00 GT cars).

The options I am considering are:
Amsoil ATF
Amsoil Synchromesh
GM Synchromesh

The Amsoil synchromesh is listed as an MTF, but the T-45 is supposed to use ATF? Can anyone provide a definitive answer?
Thanks

 

[VTGT91]

The T45 transmission does require ATF. The clearences are so tight in some places that it cannot be properly oiled by thicker manual trans fluid or gear oil. I just did a complete rebuild of my T45 and used Mercon V as the fluid.

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[Night Shifter]

I ran penzoil synchomesh in my t45 with no issues whatsoever...shifted smith and ran fine....I use it in the t56 now

 

[GDawg]

I run Royal Purple Synchromax.

 

[bhuff30]

I went with Mobile 1 synthetic ATF in my T45. I bought it in the store, and have had good experience with mobile 1 oils. Probably cheaper than royal purple.

 

[rconaway]

please delete

 

[jmc01gt]

I used RP Synchromax, noticed less heat and smoother shifts on my T-45.

 

[gt00]

I use Mobil 1 and it works great, and costs a lot less than GM Synchromesh.

 

[rconaway]

I also used Mobil 1 and my T-45 is still running with 400-650rwhp at 80K miles. I doubt few cars have been abused this much on various tracks and WFO runs for 30 minutes. I've even had to replace the rear bearings as those have been worn out in this process. Tranny still works like a champ. My money is on Mobil 1.

On another note, I used Mobil 1 auto fluid in my Windstar. I've towed 6000lbs with that setup for 2000 mile stretches and the car went 180K with no problems. Another Windstar I have with less miles has written off 4th gear. This Windstar had standard tranny fluid and changes. I used Mobil 1 in several cars up to 250K miles with never a single problem.

 

[mransr]

I use Royal Purple Synchromesh and after nearly 1/4 of a million miles the trans is still working flawlessly (well, as flawlessly as a T-45 can)...

 

[chunger]

Wow, looks like I'm in the minority. I've run GM Synchromesh for a couple of years in mine.