TEST VEHICLE / FLUIDS TESTED

-2004 Cobra T56
-Non synthetic ATF
-Amsoil syncromesh
-Amsoil manual trans and transaxle fluid
-Chrysler Viper spec trans fluid

Non syn ATF

-good cold shifting with no notchiness, shifts fine hot. Very cost effective to use, recommended as the factory fill.
-downside, trans noise varies between noisey to very noisey depending on temperatures. Trans smoothness falls off sharply after a single track day.

Amsoil Syncromesh

-ok cold shifting, gets even smoother as it warms up and is good once hot. Nice improvement over ATF.
-downsided, trans noise is minimal when cold, does increase to about 2/3 of ATF level when hot. Trans noise does however increase to virtually equal to ATF after one track day. While shifting smoothness does not fall off as much as ATF, it does drop off an appreciable amount.

Amsoil manual trans and transaxle

-shifting cold falls somewhere between ok and good but only takes a block or three before it becomes silky smooth. Cold or warm, trans noise is hugely reduced.
-downside, none as of yet. Will see if it continues to control trans noise after the fall lapping day.

Chrysler Viper spec

-shifting cold is definitely not as good as the Trans n Transaxle Amsoil but only takes a few blocks before it equals out. Cold or warm, trans noise is hugely reduced. After a track day, no noticeable difference in performance or noise.
-downside, cost.

IMHO, testing suggests regular ATF and Synchromesh aren't the hot ticket for the T56 (syncromesh works killer in a T5 / T45 etc). While the Viper spec does a terrific job, you can have the same performance and noise control with Amsoil's Manual trans n Transaxle fluid for dramatically less money.
I'm optimistic the Amsoil is going to work out long term, will update once I have more miles on it, very pleased thus far.

To our Amsoil guy Ryan, thanks again for setting me up and taking the chance you'd get the feedback you'd hoped for. I will continue to suggest Syncromesh for those using a T5 / T45 or 3650, seeing excellent feedback from those using it.