I just recently broke my t56 transmission. When I pulled my trans out I found that I twisted the input shaft in half. I am only putting 420 HP to the wheels. I have previously tore the trans apart and put in a steel 3-4 shift fork and Carbon Fiber blocker rings in. While it is apart I am planning on puting bronze fork pads and billet keys in it. Do I need to do the viper input shaft and mainshaft conversion since I have alrady broke the input shaft once or was it just worn out from having 120K on it? And are there any other upgrades that u guys would recommend?

 

Twisting the input shaft is not very common at that power level . What clutch do you have in the car ?

 

I have a LS7 clutch in it. Yea I was very amazed that it snapped it in half too...

 

any more comments guy??? Need input.

 

Aren't the GM T56 26 spline from the factory?

Our Ford T56 are 10 spline and we do the 26 spline swap ASAP, you'll always want more power.

 

yea they are 26 splines, I've never seen a 420 rwhp car snap the input lol

 

So is the LS1 T56's input/main shafts made of a different material than the Viper's?

As far as I knew, the only thing a Viper trans had going for it was the different gearing

 

Breaking a 26T input is not common at torque levels well above yours. What condition was the pilot bearing? Are you using a std bell? Are the dowells there? Something "helped" break this and you should look for it/ solve it before you throw anothe trans at it.
Later Vipers ( 04-on)have a sigle piece cluster gear and they do have different input material (9310 over 4615) besides gear cuttings.

 

I am using a stock bellhousing and the line up dowels are still there yes. And yea i just got off the phone with Amber from six speeds inc and she said to do away with the roller pilot bearing and use a bronze pilot bearing. And yes I agree with you I still need to do investigate everything before I fix everything and later run into the same problem.

 

I don't see a pilot bearing causing the issue but its remotely possible . Can you post a picture of the part of the input shaft that went into the clutch ?

 

...and does the rest of the transmission still turn freely, by turning the output shaft, or what's left of the input?

Seems more likely that something locked-up inside the trans and seized the input.

Has the trans been opened up again after this latest carnage?

 

the trans still goes through 1-6 and reverse perfectly fine. And no I havnt opened the trans up yet but will be soon. Here are a few pics of the input shaft on the trans side. I havnt pulled the bellhousing, and clutch out yet.

 

The pics aren't very well focused on the input shaft damage, but it doesn't look like a twisting tear, but a shearing break.

Who did the recent rebuild of the trans? Something doesn't seem right, either with the pilot support or the end-play of the input shaft to cause it to have a shearing force on the input shaft??

 

What tire is on the back of the car ? Is it a drag radial ? Did you get some wheel hop ?

 

I am just running street tires. And here are some pics of the other side of the input shaft sorry bout the quality they are on my phone.