Just curious, I will eventually have a local transmission shop rebuild my Olds th400 transmission to withstand 450-475 hp and about 550 foot pounds of torque. What are the weak links in a th400? I've heard the sprag gears are a weak link but I know there are guys here who know th400's.

This car won't see any track time but I don't want to blow it up either (transmission). Any suggestions,tips etc would be appreciated.

Thanks!

 

T400 built to stock 1967-1970 442 specs will hold up just fine. Add an external trans cooler, heat is the biggest enemy to a T400

 

The sprag you refer too is probably the weakest part I've heard of but overall the trans is pretty beefy. Several companies make a 34 element sprag that is over twice as strong as the 16 element one. I also know that holding it in 1st gear to do a burnout (such as at the drags) is a no no. Shift it into 3rd as soon as possible in those situations.
I don't know the specifics but it has something to do with the internals changing direction on the 1-2 shift. I actually hope someone responds to this with more knowledge of this issue. Wouldn't this happen on normal acceleration also? Why is it worse in a bleach box than under normal conditions? I look forward to this thread.

 

Trip that's exactly what I heard don't do burn outs in 1st gear, I heard to do them in 2nd is better because of the sprag. Hopefully someone else will chime in.

 

In fact if you're able to start in 2nd it's better. I have a full manual TH400 so that is easy for me.

 

I upgraded to the 34 element sprag on mine when I rebuilt it and also run a trans cooler. In the meantime I added a Derale pan with cooling tubes and drain plug. Adds about 1 qt extra fluid also. Does it work? Or hype? I don't know. But I added it anyways.