Amsoil 75W90 in Tremec?

[JCoop]

Originally Posted by Bob In Ct

Hey guys, keep in mind that a 30 WT motor oil has about the same viscosity as a 90 WT gear oil (give or take, I don't have a chart in front of me). Motor oil does not use the same scale a gear oil, it uses a lower one.

I've been using Redline MTL in my Tremec for 5 years with no problems. Tremec recommends Syncromesh by GM.

Bob

So that means the 75W90 Amsoil is equivalent to like a 5W40 motor oil...
Which now makes sense. Anyway, I just ordered GM synchromesh but Ill keep the Amsoil in a jug when I drain it. ($30 synthetic flush...geeez)

[JCoop]

As a follow up, I changed the Amsoil to GM Synchromesh Fluid as recommended (by Tremec) and I have to say, she shifted much better and smoother on the Amsoil 75W90 synthetic.

Wonder if Three Peaks has more info on the "paper-backed synchro plates" that require ATF to function properly...