You ever heard this one?

In the coments on my video one guy said:-

What wtf!?!? you did not press the clutch?!?! Did you do the clutch switch mod to protect your jz from crankwalk?

New one on me, any truth in that? or a load of bollox?

http://www.youtube.com/watch?v=jTqKbs-yfGs

suprised that the clutch switch mod is not done on your high powered car

afaik US Supras had a switch on the clutch that meant they couldn't be started without the clutch pressed in (for added security). It turns out that doing this can wreck the engine & cause crankwalk. There's a sticky thread on Supraforums about it.

The mod is either bypassing the switch or moving it to the brake pedal.

edit :- http://www.supraforums.com/forum/showthread.php?t=465008

and this;

http://www.supraforums.com/forum/showthread.php?t=56195

clutch switch is normally used to drop off torque levels on gear changes via ecu.

The us cars require the clutch to be down to start the car. an aftermarket clutch with a high pressure clutch plate can cause the thrust bearings to wear out very quickly.

They bypass this so you don't have to start the car with the clutch down.

The US have a lot of problems, but crank thrust bearing wear is more than likely due to a National habit of riding the clutch, from my fairly limited experience of Americans in manual cars It's not good practice to start a car from cold with the clutch depressed though, as the thrust washers will be fairly free of oil until the engine fires, as they drain down more easily than the shell bearings.

http://www.mkivsupra.net/vbb/showpost.php?p=2554079&postcount=79

Wow you learn something new everyday

Wow you learn something new everyday

Very true, have never heard any of this

I find it helps to be clutchless these days!

Well, I quess the answer is your don't have an American Car Jamie!

Might be worth moving to Technical?

IIRC this has already been talked about in tech many moons ago. Suffice to say it seems to be more prominent in the US of A.

The us cars require the clutch to be down to start the car. an aftermarket clutch with a high pressure clutch plate can cause the thrust bearings to wear out very quickly.

 

They bypass this so you don't have to start the car with the clutch down.

I remember when i bought mine and Lee was telling me about this.

Yeah! i have seen this over on the Supra forums, the dozy buggers where blaming the oil seal failures syndrome on it, it does wear the crank thrust bearings, but as for causing seal failure well the crank would have to be able to move in the region of more than 5mm in order to have any impact on the seal, or pump.

My new Skyline has this, it was the first thing i disabled;)

Just read alot about this on this SF forums and the americans have had this issue even on stock engines.

Seems that the problem must occur with pressure plates that are to strong.(RPS)

Talked to Andy from Southbend that says the 4000 punds that the RPS do is way to much and they never go any higher than 3300 pounds with theirs.

If the crankwalk happens, thats a new block, so might be worth checking out.

Im on a RPS carbon carbon, very light, as light as stock id say.

As has been discussed though, it's not a problem for UK, Euro or J-spec cars as they don't require the clutch pedal to be depressed when starting the car.

With the engine running and with an oil system in good working order it shouldn't be a problem if the clutch is used in a proper manner.

i allways press the clutch to start my car, just habbit, should i not?

Just strange, that so many overthere have had the problem and even some of them are J-spec models and still have had the crankwalk.

And even if they did the Clutch switch bypass, then it still happened.

Just wanted to see if there was some more info about here..

i allways press the clutch to start my car, just habbit, should i not?

Yes you should stop.

Basically there is a pivot attached to the gearbox bell housing that the clutch fork pivots around. When you put your foot on the clutch the clutch fork rotates about this pivot and pulls the clutch plate towards it.

The clutch is in two parts and held together by springs. One side is pulled upon by the clutch fork (and creates a gap so the clutch disk can spin freely) the other side is bolted to the flywheel.

The flywheel is bolted to the crankshaft, and what stops the whole assembly from moving when you pull on it with the clutch fork is the thrust bearings.

The thrust bearings are 4 pieces of metal about 3mm thick fitted either side of the number 4 main bearing, and are normally lubricated when the engine is running.

With the engine stationary the oil runs off the bearings, so when you go to start the engine, if the crank is being pulled up onto them, they'll wear.

Once you have slop in the system, you'll have crank walk. Not good.

Im on a RPS carbon carbon, very light, as light as stock id say.

Most that have had the issue are on the stage 2 with the blue PP.

They all say that if you have a multidisk clutch, then you should be alright, since this will easy the wear on the bearings.

Just strange, that so many overthere have had the problem and even some of them are J-spec models and still have had the crankwalk.

 

And even if they did the Clutch switch bypass, then it still happened.

 

Just wanted to see if there was some more info about here..

It won't be every instance, but I imagine a lot of it is to do with not shifting into neutral when stopped, and basically riding the clutch.

Even with a perfect working oil system, if you drive around leaving it in gear all the time you'll eventually wear the thrust bearings.

Yes you should stop.

 

Basically there is a pivot attached to the gearbox bell housing that the clutch fork pivots around. When you put your foot on the clutch the clutch fork rotates about this pivot and pulls the clutch plate towards it.

The clutch is in two parts and held together by springs. One side is pulled upon by the clutch fork (and creates a gap so the clutch disk can spin freely) the other side is bolted to the flywheel.

The flywheel is bolted to the crankshaft, and what stops the whole assembly from moving when you pull on it with the clutch fork is the thrust bearings.

The thrust bearings are 4 pieces of metal about 3mm thick fitted either side of the number 4 main bearing, and are normally lubricated when the engine is running.

With the engine stationary the oil runs off the bearings, so when you go to start the engine, if the crank is being pulled up onto them, they'll wear.

Once you have slop in the system, you'll have crank walk. Not good.

thanks for that, ill put a postit on the wheel for a while to break the habbit

A friends uk spec manual had this fitted (was a brand new stock uk spec, back in '96) seemed factory fitted as he didn't have aftermarket security.

Only manual supra I've seen in the uk with this. Would be nice to know if the old girl is still on the road. He got rid of it on 2000 due to the engine blowing apparently, and he "upgraded" to a sc430