Samurai Speed's Transmission Dissected

We've been very busy with the renovations on our new shop that we hadn't had a chance to dig into our broken tranny. That and the fact that we ran into some problems with pulling the gears apart -- we had to send it out to someone to have it done as the gears are pressed on super tight.

Well, we finally were able to get it apart and take a closer look at it. Big thanks to Eddie, our head mechanic, for busting his butt on it.

Here are some photos where you can see the damage to the first gear itself as well as the gear shaft...







After closely examining the broken first gear, and seeing a pattern of hairline cracks in different places throughout the gear, it is our conclusion that the damage to the gear is most likely NOT from wheel hop. (Hence the reason there was no wheel hop on the launch that it broke.) It appears as if the residual damage is simply from LAUNCH CONTROL ITSELF.

The LC process seems to put so much pressure on the gear that over time it produces fractures and then ultimately the teeth break off. Using launch control then becomes like RUSSIAN ROULETTE... if the gear comes to a stop where you are about to perform another launch, and that position on the gears does not contain an existing fracture, then you'll most likely not experience breakage from that actual launch; however, that new launch could certainly produce new fractures of the gear near that position where most of the stress was placed from LC.

Remember how my car had over 100 launches on it? And yet others broke from 20 or less launches? It's literally called LUCK. It my case, the gears happened to not come to rest (before another LC was going to be performed) where previous fractures had occurred. So the pressure that new LC would put on the gears was being done just as if the car had never been launched before. It was literally like playing Russian Roulette. If the gear came to a stop directly on top of an existing fracture and you launched again, your odds were very high that the gear would break on that launch. Not always the case as some spots possibly took multiple launches with existing fractures, but it certainly appears that if you happened to stop the car with that pre-fractured area of the gear teeth lining up on the gear shaft and you went to launch the car that it was most likely causing the breakage.

So it certainly appears that it's not just wheel hop causing the damage and that it's the pure force of launch control itself that was putting the stress on whatever teeth were lined up on the shaft at the moment of impact. Bottom line... the gear materials don't seem to be strong enough to withstand the force of launch control.

We're now in the process of having a stronger first gear and shaft made... not only of stronger materials but also cryo-treated. Once we get this made my goal is to take the car out and do 100 LAUNCHES IN A ROW on the same day. We'll have to let the car cool down with temps, etc. when needed, but the goal is to bang the hell out of it to really test it. Then we'll open the tranny back up and analyze the condition of that 1st gear and shaft.

We'll post more news as it becomes available.

Samurai Speed's Transmission Dissected! - NAGTROC - The Nissan GT-R Owners Club

 

about time someone figured it out

guess this is gonna stop everyone from using LC

 

thanks for the article sid!

i read this from jalopnik.com:
Nissan GT-R: Nissan GT-R With Updated Launch Control Still Fast
nissan made some LC adjustments to reduce the stress that it causes to the synchros. the result? more traction and a faster GTR... of course Porsche won't believe it and will contest that claim till they've started foaming at the mouth

 

that sucks and i heard nissan won't warrant the transmission if you use LC

 

that's true, but subaru won't warrant the sti's transmission either if you dumped the clutch between 5-6k all the time.