Help! Gears Getting Stuck After Hard Launches

[Brezza]

Hey guys,

I am just having a problem with the GTR, its a 89. It's currently got 350rwkw and is running a standard box and a Extreme clutch kit. From memory the clutch is a cushion button 6 puk ceramic clutch, 1600kg pressure plate, chromoly flywheel. it has been rebuttoned once when the ceramic plates were put on instead of kevlar, and the flywheel and pressure plate was machined.

the clutch fully engages right near the top of the pedal, i dont know whether it has worn out again? it shouldn't have because it was only repadded a year ago, the engagement hasnt really changed much.

the story goes, whenever i hard lauch the car and take the RPM up to around 7k it wont let me change gear into 2nd, it will not let me pull the shifter out of first. And yes i do push the clutch right in!

I've spoken to a few people and they have suggested that maybe the pressure plate is being pushed too far in and it is rubbing on something or making the clutch engage in a weird way and will not let me change gears?

thinking about it, it does feel similar to if you dont push the clutch in far enough and try and change gears.

could i also be maybe heating the clutch too much and it could possibly be melting to the flywheel? i was told that there have been instances where in motorsport some clutches have been known to melt to the flywheel.

i highly doubt this as it is just a street car at the time being.

Does anyone have any thoughts?

or any experiences that they may be able to offer some advice as to the possible cause?

[GTRsean]

Ceramic plate is shite, we had one in a 180sx, and managed to weld it to the flywheel twice, once at the drags and some other time. Had to pull box off to pry plate off the flywheel, second time I shock loaded it to break it free. So I'm not a big fan of the ceramic types now

Another cause could be heat buildup, causing the clutch plate to warp with heat and cause lack of full disengagement. That will cause hard shifting etc.

My last 32GTR I had, I bought a extreme carbon fibre twin plate clutch, car was running 350RWKW or so, was a great clutch.

My other favorite was an os gikken twin plate spring centre clutch. The input shaft snout needs to be machined down though.

[Brezza]

the guy selling it to me did warn me that it can weld to the flywheel in some cases, usually drifters or racers have done this. but on the street it is fine.

it does tend to happen when the engine gets quite warm and i've been driving for a while.

i was looking into getting a twin plate clutch, its just they're a fair bit expensive. but i suppose at the power level i'm at i might need it?

[R.3.2.G.T.R]

i did something similar in mine, launched the car and couldnt select gears anymore.. only able to select when car is off.. i think mine is fused.. bought nismo coppermix twin, yet to install

[Brezza]

Hey BWRGTR

keep me posted on what the outcome is once you get the old clutch out and new one in.

how much have people picked up twin plate clutches for the GTR for?

[GTRsean]

Secondhand as little as $500, or as much as $2500 for a nice new twin plate.

Jim Berry clutches seem to be very popular too...

[Brezza]

I'd be leaning more to getting a new one, that way I know that its condition when I put it in.

I dont really want to be buying a second hand one and having to rebuild it before I use it.

It'll probably cost near about the same.

[R.3.2.G.T.R]

mine cost a touch over $2k delivered from japland

[GTRsean]

I'd be leaning more to getting a new one, that way I know that its condition when I put it in.

I dont really want to be buying a second hand one and having to rebuild it before I use it.

It'll probably cost near about the same.

Good choice!

[R34Mobster]

I'm in the same situation as you ,same Extreme clutch in my GTT running 380hp not on good tune anyways,,did the same thing launched it from 4.5 to 5 RPM and it started making grounding noises ,couldn't get it into 1st gear had to go neutral then second then 1st with pedal pressed down, now couple days before it relly got worse and clutch would sort of hit flywheel similar if you let the clutch go to fast but with constant hitting even in neutral and yesterday it just seized compleately.... could not select any gears and if the car was in neutral it would still move forward until clutch was fully pressed to the floor ......

now have to put my old "HKS twin plate 1000ks.....you hate it and you love it at the same time LOL"

[Duncan]

i did something similar in mine, launched the car and couldnt select gears anymore.. only able to select when car is off.. i think mine is fused..

exactly what I managed to do in a race. clutch was welded to the flywheel.

removed, machined, reinstalled and it is fine now.

no reason to replace a clutch if this happens....just avoid getting it so hot, and make sure the clutch is bedded to the flywheel properly (ie both flat, mine took a few ks after machining it to come up OK)

[R.3.2.G.T.R]

exactly what I managed to do in a race. clutch was welded to the flywheel.

removed, machined, reinstalled and it is fine now.

no reason to replace a clutch if this happens....just avoid getting it so hot, and make sure the clutch is bedded to the flywheel properly (ie both flat, mine took a few ks after machining it to come up OK)

bugger, i have already bought a new clutch thinking mine would be useless, i have terry@award fitting it in this week

[T04GTR]

yes a very common issue. all the "brass button" type clutches these days tend to melt to the flywheel.

they bond on the outer diameter of the friction plate. evan worse if its a molly flywheel. they really need to be "worn" a fare amount to be reliable to launch.

just like bedding in brakes. the need to get hot and burn off all the resins etc etc otherwise they get sticky.

[R.3.2.G.T.R]

ok, mine did weld itself on, few pics below

out with the old nismo single plate rebuilt by NPC

in with the new nismo twin plate coppermix goodness

anyways, i had my single nismo rebuilt by NPC a few years back, never was told it was button clutch, so obviously i slipped it here and there and killed it after launching it once since its been in..

as for twin plate, picked the car up yesterday, planning on bedding it in for 500kms or so, nothing but a pleasure to drive, soft pedal but i like it, no rattling, just smooth pickup, so very happy, got terry@award to install it and done in one day