The Nissan GT-R transmission is catching a hard time on the interweb. There doesn't seem to be a post anywhere, on any forum that doesn't mention the problems that some people are having with the transmission. Owners are vowing not to use launch control. Some are afraid of the transmissions just giving up on them. Widespread panic...well maybe not panic. One of the members from the NAGTROC forum is reporting the price of the transmission assembly is going up from 1.6 million yen to 2.5 million yen for cars that come from outside Japan.
My thoughts are that wheel hop is killing the transmissions. The problem with the wheel hop is with launch control, the GT-R spins the rear wheels. The wheel hop is exacerbated by the launch control. How do you stop the wheel spin and wheel hop ? You don't use launch control. This has been touted as a feature of the car and results in world beating 0-60 and 1/4 mile times. Some of the owners that have used launch control often, have broken transmissions and are now been denied transmission replacement under warranty. This is a tough subject. The line between abuse and doing something the car was built with. So what does Nissan do to fix it ? Damage Control. Damage Control is keeping a problem from getting worse.
1)Get rid of launch control. This will make no one happy. 0-60 times and 1/4 mile times will not be as "published". Doing this will not make anyone happy, and will cause a lot more problems.
2) Modify launch control. If they have the car launch at a lower RPM, it will wheel spin less, and cause less potential for breakage. The problem here again is that the cars will be slower, people will complain, magazines will complain. On low grip surfaces, there could still be issues with breakage.
3) Modify launch control 2. A little wheelspin in an all wheel drive car is the quick way off the line. Instead of turning the traction control OFF, the car could still have control of the rear wheel speed and keep the rear wheels from spinning and hopping so much on a launch. Traction control doing what traction control should do.
4)Make the transmission- differ- clutch- transfer-rear end serviceable. Send it out to someone and have them repair the broken parts. Automatic transmissions are rebuilt and returned to service, the GR6 should be the same.
5) Make the parts cheaper to replace. One broken gear does not a $20k transmission make. The gear and counter gear in the transmission would be $1000 in parts. Even at $5000, I don't think a lot of people would complain too much about replacing transmissions.
6)Try a fluid change. The transmission uses an ATF type fluid. Its thin. It offers little protection for shockloads. The same fluid is also used to provide lubrication and cooling for the clutches. For the older GT-R's I use Redline Shockproof Heavy gearoil in them. It seems to help cushion the shockload. I wouldn't put Shockproof Heavy in a GR6 transmission. The V160 in the Supra and R34 does not like it much either. It causes shifting problems.None of the Shockproofs seem to be recommended for Synchro transmissions, but in a R32/R33 GT-R application they work out fine. Redline sells three viscosities of the Shockproof:
similar to a 75W250 grade, while providing the same low fluid friction as an SAE 75W90.Lightweight
Similar to a 75W140 gear oil, but with the lower internal friction of an SAE 30 motor oil.Superlight
A unique product with the viscosity of 75W90 gear oil but lower internal friction similar to that of an ATFThe side benefit could be the clutches might be able to hold a little bit of a higher load without slipping.
7)Change the fluid path in the transmission. Separate the clutches from the gear set. Use a different fluid for the clutches and the gears. Something a little thicker to help out some of the shock loading. The clutches can keep their ATF.
8) Fix the wheel hop. They need a suspension engineer dedicated to figuring out why the car is wheel hopping, if that is actually whats killing the transmissions. It can probably be fixed, it might not be able to. It might be able to be done though spring/ dampening changes.
9) Try a clutch engagement change. If the clutch slips more, the tires spin less. Less wheel spin equals less wheel hop. However the issue now would be the clutch will not last as long. Since the whole transmisserdifferclutchrearend is an assembly, things don't change much. Its still a $20k part to change when the clutches need replacing. The transmission ECU does control how much and when the clutch locks up. This programming could be altered to smooth the launch off the line.
Thats the first ideas I have come up with.