[Dean Stillie]

broke the input shaft . Anybody please chime in if you have ideas on making it last. So far I got polish the rough part of the shaft , not too sure about heating to remove some harness. Not wantin to switch to 904 shaft just yet. I will be turning the line pressure down a bit
. Shifts really hard into third and it broke right after a hard shift into high

 

[bn880]

Boy, you must have really hooked up... Thankfully in automatics this is less of a problem.

 

[Dean Stillie]

Boy, you must have really hooked up... Thankfully in automatics this is less of a problem.

Nope that was with street radials no hookage just breakage.
Broke after shifting into 3 rd

 

[speeduphoria]

Boy, you must have really hooked up... Thankfully in automatics this is less of a problem.

this is a 3spd automatic, It happens more in automatics

 

[DblTrbl]

Steve Lockett has been having good success with heat treating (although he is currently using a 904 shaft). He said he had problems when he got to about 600 whp.

I hear the the lockup shafts may be made of a stronger material than the non lockup. I wonder it that's true.

I also heard that someone out west just broke a 904 shaft. Go figure.

I'm currently using a heat treated, smoothed lockup shaft.

What line pressure were you at when it went?

 

[Dean Stillie]

About 165 I have turned down. Still shifts really hard into third though. I was looking at a lockup shaft and it is thicker longer at the drum end less deflection I bet. Less of the rough machined area from the seal to the splines.

 

[DblTrbl]

I'm going to stay a bit lower, in the 130-140 area unless is see major slip in the logs.

It's the change in the engine speed from 2nd to 3rd that the big shock. I'm going to try to lockup 2nd gear so the delta from 2nd to 3rd is not as dramatic.

 

[jim34]

It does look like a deflection break, reminds me of a snapped drive axle from too much susp travel