I have dex 3 castrol sun tec in there now I was wondering if I should use another atf 3 such as castrol,mobil 1 or amsoil, or should I use teh amsoil,redline royal purple or gm synchromesh. I don't want to shorten the life of the tranny at all. Thanks

 

The fluid won't matter that much, its the beating it that kills t-5s. I won't use anything with a bunch of additives. Just your regular dexron III would be best.

 

So mobil 1 amsoil or castrol syn tech should be fine?

 

From what I have read, and inquired about, Dexron should be fine, but under sever use/driving conditions I would go with a synthetic alternative like the mobile, red line etc....I just finished rebuilding my WCT5 and intend to run the car on the track, synthetic fluid should help keeps temps in the trans down etc...etc and provide all the other 'benifits' of synthetic fluid.
-Andrew

 

I see the red line royal purple and amsoil all make a mtf or a sycromesh fluid they recommend i just don't want to hurt the trans, it was beefed up when it was rebuilt and it is the nicest shifting tranny I have ever used( I have used alot of them).

 

sorry to highjack but what oil does a non WC need? in the computers at work it says it takes dexron 2 automatic trans fluid but someone told me it needs a 80-90w oil?

 

DexronII only applies to WC units. They require it because there's a fiber/paper clutch lining in the synchro assemblies that's the same material as the clutches in an automatic trans. Non-WC units require 80-90 wt. gear oil. The bearings in the non-wc trannies need a more viscous lubricant, hence the need for gear lube. I've also heard of people running 30 wt. motor oil or even ATF in them, but GM says gear oil in the shop manuals. They probably shift a little slicker with the lighter fluids, but it could be detrimental to the life of the bearings. Btw, Synchromesh is what Tremec says to use in their TKO trannies. I don't know if it's good for T5's or not.