Help On Finding Transmission Problem

[Peacekz]

Hello Everyone.
Please help me identify problens with my gerabox.
I have a BNR32, with nice built RB26 and S362FMW runing 1.2-1.4 bar of boost.
I have broken 2 sotck trannys so i ordered OS-giken 5 speed kit with input shaft and center plate.
Installed it and my problem seem to go away... until i get to drag strip.
While making my starts better and better tuning launc and torque split finaly i set up launch to 7200 and forgot to remove 50% fo torque from front i didn ont start at all, the car didnt even moves.
later in garage we found that it is counter shaft broken right after 5 gear.
Here is a picture

If you look closely you can see wear on the shaft in the place it inserts into a wall between gearbox and transfer case.
What can be the cause of this? I mean the cause of breaking shaft i guess wear shows that shaft was not proppely secued and had a play.
All kind of bearings including bush in the crankshaft?

Edited September 16, 2014 by Peacekz

[89CAL]

You haven't listed your power, which really tells more of the story then how much boost you are running. Depending on power/torque, with a 7200rpm launch with power going to all 4 wheels, it might just be something that should not have been done.

Better photo of the fracture?

[Peacekz]

Hello Sorry no better foto.

I dont know exact power. it should be around 600 HP i think taking in consideration i load 89% of 720CC injectors and making 11.4 ET with bad start.

Soru english is not a native, what do you mean by fracture? the place where i see a wear on the shfaft where it contects needle type bearing or the photo of the the shaft where it was broken?

Yes i understand that was my mistake to launch on 50/50, but i'm quite expiriencde in gt-r's and never seen countershaft failure like this. There is always a weaker point than these solid 29mm stell shaft.

[89CAL]

Photo of the break in the shaft. Should be able to tell a bit about how it failed

[Peacekz]

I will make a better fotot later.

It looks like it was cut very fast no curves from twisting. For me it looks like it is cracked perfectly. But i did'nt look detailed to it. Will post later

[Peacekz]

[Peacekz]

SOrry for miss-telling The shaft i tell about is called Mainshaft.

[89CAL]

The middle shows the last part that hung on then twisted and snapped. Will have to find my failure analysis book, haven't had much to do with metal failures lately. That is a very clean break. I had a similar looking failure with a rear drive shaft. Almost identical actually.

That was from a high rpm launch

Edited September 17, 2014 by 89CAL

[Peacekz]

SO Most likely it is due to Over-power?

[Peacekz]

One more thought -the break surface is polished by rotating during the car was worked. And we pulled the car to the garage with the engine started so the brakes was good. So i guess the surface will not tell the truth. I guess the shaft was broken due to it has a vertical play.