what tranny code does my T5 have in my 91 RS 305 TBI? and how much Dextron II Fluid do i need to buy to replace the fluid? thanks!

 

Use Dexron 3 at a minumum.....but you're much better off getting Mobil-1 synthetic Dextron 3. No Dexron II!!

You'll need 3 quarts I think...

EDIT: You should have a WC T-5 if it's original.

 

i've always used m1 or amsoil gear oil, never had a problem after many many miles. i believe gm switched to atf more for milage improvement that anything else

 

that, and the fact that there are friction surfaces on the WC synchros that are not unlike those found in an automatic.

 

So should I also use Dextron 3 in my NWC T-5?
The tranny is from an 84 TA donor car.

Thanks

Al

 

Gear oil or lube is to thick for T5 or WC T5, its just not thin enough to flow right. Would be like using gear lube in your engine, I bet it would run ok too.

 

Dexron III would be fine.

 

GM themselves waffled back and forth on this very issue a few times.

The first year or 2 of the T-5 they spec'd gear lube. Then for a year or 2 they spec'd ATF. Then they went back to gear lube. All of this, mind you, was without so much as the slightest change in the parts that were in the trans.

We all suspected (though of course have no way to prove) that the reason for the ATF experiment was for gas mileage, and the return to gear lube was due to a rise in warranty claims. Keep in mind this is pure guesswork.

The 2nd design T-5 uses composition facing on the clutch surfaces of the blocking rings; and GM as well as other auto mfrs have always spec'd ATF for those. However, lots of us (myself included) have been running gear lube in them for many many years without trouble.

Gear lube will give better lubrication than ATF, especially on the gear teeth and roller bearings, so the trans can be expected to live longer. On the other hand, ATF will give lower losses, better gas mileage, and slightly higher RW HP.

It's your choice.

 

My T56 runs ATF too. I pulled it apart to verify the condition of the internals before installing it into my car. After 50,000 miles there was no appriciable wear on any surface.

Given the endplay specifications in the T5 and T56 I can't see running regular gear oil. In fact, a friend of mine destroyed the T5 in his Cobra by doing just that. Synthetic gear oil may be different, because it seems to flow about like ATF. This may offer better shock protection than ATF, but I worry about the cones and synchros.

I run Amsoil synthetic ATF and love it. I shy away from Mobil 1 products because I've had seal leak problems with their oil in two different cars.

Dextron III is all you can buy now from what I've seen. Dextron III has superceeded II and I. Soon III will probably fall by the wayside in favor of IV.

 

Sounds about right. I tried running non-synth gear oil in mine since it was one of the first years supposedly "spec'd" for that type of oil.

But I had too many problems with gear clash when the oil was cold - and it took at least 20 minutes of driving till it warmed up and started acting better. I know I was also not helping my synchcros while running cold either. Clutch adjustments had no effect at all on the gear clash. Then I ran Mobil 1 dextron III fluid and all the probs went away....