Thread: Dowel for engine to transmission mating

i was going threw clutch in what seems like 3-6 months till figured out why. :o but i upgraded and replaced a lot of needed parts in the porgress. lol

http://www.sr20-forum.com/vvl/27412-another-clutch-blown-missing-dowell-pins.html

I actually found a bunch of threads on clutch explosions etc... on dowels not being in for the trans to engine mating... but honestly..... how the hell do 2 dowels missing for alignment do this? I'm not saying it isn't the problem but really... what's the science behind that?

Just to get the info right, I'm not talking about the dowels on the pressure plate to the flywheel...

I just ordered 2 new ones from my local stealership... waiting to install...

If you havent noticed, the holes in the trans are larger than the bolt, the trans has probably a good 2-3mm movement in each direction without the dowel pins that you could still get all the trans bolts in and it would look like its on just fine but probably sagging a little or a little twisted clockwise or counterclockwise. In other words, the input shaft wont be centered on the clutch and this will put tremendous pressure on the disk itself. Once engaged, if the clutch isnt sitting perfectly center on the flywheel and pressure plate you will have a very very heavy vibration on the clutch disk and input shaft due to spinning in a not so perfect circle. Basicly while at one part it sits nice and even with the input shaft while at the opposite end it pushes outward or pulls inward on the shaft and the disk gives before the input shaft. Plain and simple. If you still dont understand it, I will draw you a picture.

slight miss alignment, even .005", will cause the clutch disk to be miss aligned with the pressure plate because the disk is supported by the input shaft and the pp/flywheel are supported by the engine. You can move the tranny around a LOT with the bolts loosened and no dowel pins.

Again this is exagerated to make a point. Doesnt matter if its only a mm or two off center, it will actually equate to 4mm total movement in a stressing postion on the disk. You have an input shaft that wont move. The flywheel (grey part) turns in a perfect circle. The disk stays in its relation on the flywheel while the input shaft tries to stay right where it is in the picture because its stationary just trying to rotate. So guess whats going to give first, for one its going to put tremendous stress on the input shaft bearing two the majority of it is going to be sucked up by the disk itself, primarily the springs and hub part of the disk.

that's the best discription i've seen.

One is pressed into the tranny and one is pressed into the block. Maybe the one in the block was there but you did not notice it?

Actually they both go into the block. But a lot of times when removing the trans it will come out with the trans. They can easily be removed from either the block or the trans.

But they belong in the block. Also helps keep the spacer in place as well.

^Yes. It's in my pics.



^This is what I figured.

I took a dowel pin to the local hardware store and found one that the same od and length. They had it in neoprene or aluminum, so far no problems at all and the tranny went on easy.