Hi Fellas. Been a while since I've posted here. We've got an '80 280zx that we race in the 24 Hours of LeMons series. Our last race was almost exactly one year ago, and somehow we miraculously won our class and placed 8th overall out of 240-something teams. Mind boggling!!

This was made even more amazing by the fact that in the last few hours of the race it sounded like somebody had emptied a bucket of loose bolts into the transmission bell housing. This was noticeable only when in neutral or the clutch pedal was depressed. If the clutch was engaged and the car driving, the sound disappeared. At a halt though, the sound was loud and excruciating. If we weren't vying for a win we would have shut off the car and called it a day.

Fast forward to now (the car has been idle since then) and we are trying to figure out what went wrong. We've pulled the transmission and don't see anything obviously wrong. Today I didn't have a good enough impact wrench with me to pull off the flywheel but I did notice that there's probably upwards of 1/4" fore-aft movement in the flywheel. There is also a little rotational play, but only a slight amount. I've not been able to find a spec for fore-aft play, but the amount we are seeing just doesn't seem right. However, since it is bolted directly to the back of the crankshaft, I don't see how this is possible (the front pulley does not move when I moved the flywheel front to back.) And, given that we are still able to get power to the wheels, it doesn't seem like the crankshaft could be broken.

Any guesses as to what could be going on here? I'm perplexed. Thanks guys.

Tom

 

There should be a thrust bearing for any crankshaft (I've never had the L block apart, but in my experience, usually one of the centre journals has the thrust bearing surfaces on it) so the push-pull should be measured in thousandths! It sounds like one of the thrust bearing surfaces exploded (probably the one that supports the rear movement of the crank, the clutch should push forward gently with the transmission, I would think, but who knows...) so maybe it is grinding against the block when the clutch is opened... Might be either a good time to drop the pan, or at least stick a camera into the drain hole...