V8 4runner Clutch Problems

[twisty_toy94]

I've done over 1000kms in since installing the Lexus V8 into my 4Runner. For the first 1000kms the clutch was fine, the pedal felt nice and engaged nice, with no slipping.

But it the pedal/clutch has slowly gotten worse over the last week. It has gotten really sticky and engages really rough due to the pedal not releasing smoothly. (hope that makes sense). Its so hard to drive and either stalls or buunyhops or chirps the tyres when taking off.

The clutch is also making a noise (under load in low to mid revs) like a thermo fan hitting/rubbing on the radiator. I though it was actually the thermo fan, but after spacing it off the radiator the noise was still there, and there was also no noticable damagae to the radiator.

Anybody have any ideas what this could be before I bite the bullet and pull the gearbox out??

My thought are the bellhousing (Dellows - Supra to 1UZ) isn't square so the clutch and input shaft don't match properly with the flywheel, causing something wierd to happen?

Or the sleeve that the thrust bearing is on, is catching on the input shaft for some reason??

Any info would be great.

 

[Zuffen]

I'd lean toward a failed Diaphram. If a finger bends it will cause uneven engagement and it could be rubbing to give you the noise.

You lose the noise as revs build due to the general increase in sound level.

I think you're looking at dropping the box.

 

[twisty_toy94]

Zuffen, what exactly is the diaphram? Is that what Direct Clutches would have played with to increase the clamping pressure of the clutch?

One other wierd thing with the clutch that I forget to mention is when the motor turned off the clutch is smooth as, soon as you start the motor it gets sticky.

 

[Zuffen]

Twisty,

The diaphram is the spring that creates the clamping pressure.

When you look at the pressure plate from the rear (the gearbox side) you will see it has a hole in the middle (around 75-100mm) inside the hole is a bunch of little fingers that radiate toward the centre and stop maybe 40mm from joining. You will also notice around the centre hole a polished circle. This is where the thrust bearing presses against the diaphram. As it pushes the centre forward the outside moves back (it's pivoted around the outside) which releases the clutch plate.

The diaphram is what the clutch people would have worked with to increase the clamping pressue.

The clutch doesn't do much when the engine isn't running. When it's disengaged it allows the gears to rotate slightly to make it change easilly. Once the engine starts it does basically the same job but the synchros in the gearbox let it all the gears engage easilly.

One interesting point on a diaphram clutch is it can disengage automatically if the engine revs hard enough. You will find most race cars use a different type of clutch. Usually referred to as a Borg & Beck Clutch. iI uses different styls springs to do a similar job. When I say revs hard I'm looking toward 10,000 rpm.

 

[twisty_toy94]

Thanks for the info Zuffen...I know what your refering to....

I spoke to Dellows yesterday and they haven't heard of anything like this happening before.

The only thing he could suggest is, before pulling the gearbox out, was to buy some litium spray grease and try to spray some on the input shaft where the thurst bearing carrier slides up and down. There is a slim possibility that this might be whats causing it.

He said its most likely not that, but its worth a try before going to all the effort of pulling the box out.

I'm hoping to try this tonight. If it doens't work, I'll pull the gearbox out on the weekend, bugger.

 

[Zuffen]

Twisty,

Be carefull with the Lithium as if you get it in the clutch proper it's buggered. Then you can say bugger!

 

[twisty_toy94]

Will the Litium Spray Grease has seemed to of almost done the job. The clutch deffinetly felt a lot better this morning on the drive to work.

I ended up removing the slave cylinder on the side of the bellhousing which gave just enough room to see the pressure plate and also the pivot ball. So I gave the pivot ball a bit of a spray with the grease, and also sprayed some up the back towards where the input shaft woud be. I was careful not to get it near the clutch like you said Zuffen, as I can't see that doing wonders for it.

The pressure plate and diaphram looked fine, as in no noticble or unusual wear marks. There were some scatches on the outer housing of the pressire plate, but I suspect thats from me storing it in the garage while the truck was off the road.

I'll drive it a bit more today, and maybe have another little spray tonight, and hopefully it all comes good. Which is going to make my weekend a lot more enjoyable.