Transmission noise, knocking, speed relative '71 240z

[Ttiger]

My son's '71 240-Z started making a noise that he describes as like a playing card in bicycle spokes. It's definitely speed relative as the noise tempo slows down as the car slows. He hears it in all gears and even when coasting in neutral. He says it's coming from under the console between the seats. I had him jack it up and turn the rear wheels manually, no noise.

He noticed a lot oil residue under the car coming from the transmission area so I thought maybe it was low gear oil so he checked and it took a full quart!. He only had one quart so he put the drain plug back in, drove back to the parts store for another quart - noise was still there. When he got back home, put it back up on stands and took the fill plug out, the oil came gushing out! It didn't dribble out when he filled it the first time!

He has tried coasting in neutral with the clutch in and out, same noise. He's heard it in gear (all of them - 4 speed) and it's always there. I thought maybe it's output shaft bearing? Front U-joint?

Any ideas?

Edited January 13, 2012 by Ttiger

[killerzombie]

same problem on my car, im thinking its the slave bearing and im planning on digging in on it next weekend. let me know if you find anything first. ill keep you updated!

[Zed Head]

The u-joint sounds like a likely source. If you can crawl under the car, take a screwdriver and stick it in the joint and lever it around. If you see any movement, that's bad. Also look for signs of rust at the rubber seal around the four bearing cups.

The u-joints on his car should be replaceable, available at many auto stores.

More oil came out after his drive because the oil expanded when it got warm. I've had the same thing happen.

zombie, there is no "slave bearing", maybe you meant throwout bearing? That would make more noise when the clutch pedal was pressed and would be more tied to engine RPM.

[killerzombie]

Yes the throwout bearing (im still learning the lingo). And it does make more noise if im on the clutch and rev the engine up. thanks for the help!