98 5 speed knocking noise, m54 vs m52b28 flywheels HAAAALP!

[OddBallNo3]

hey guys I've been running a m54 converted to single vanos from an 01 530i mated to a 98 z3 zf 5 speed, running the z3 harness. the combo worked well for a while, what started as a small ticking noise has turned into a very audible knock, at first I thought it was just the pressure plate fork rattling and pushed it off till the winter. took the slave cylinder out and put some pressure on the fork while running to take up any slack and the noise didn't go away, listening with a screw driver it sounds to be loudest by the rear at the lower shaft? mainshaft? sorry i get them mixed up. figured it was the rear bearing there that was coming apart, so since there's a plastic removable plug to see the main bearing, I figured I'd take a look at the bearing and if there was any play, there wasn't, maybe about .005. even took the time to spin it up to 500rpm or so to see if I can get it to make the noise, and nothing. so that being said, before I doom this transmission (it was a tad whiny on decell anyways so yeah) but has anyone seen that? the only time it doesn't make noise is when the mainshaft isn't spinning, at idle. ok 2nd part of this, I looked up the z3 clutch and flywheel and the 530i flywheel, they're different part numbers, where I'm seeing the same transmission behind them. anyone have any idea what the difference is? I believe I ran the 530 clutch which I **Thought** had the wrong pilot bearing in the kit, but looking up the bearing its the same for the two different cars. I don't think that would make the mainshaft make noise, but its definitely loudest at the back of the transmission, I have no issues with the transmission whatsoever aside from that knocking / rattling noise. and the oil is clean. I'm at a loss and hoping someone out there has seen this.

[TobyB]

So it makes noise all the time? When loaded? In 5th as well?
(where there is no load on the countershaft)

The 'mainshaft' is usually considered to be the same as the output shaft, as all of the
shifted gears live on the output shaft.

The countershaft (layshaft) is the lower gearset that rotates in the opposite
direction. The bearings for it are often the first things to fail in most
transmissions, as they are space constrained and heavily loaded in low gears.

The clutch would be really hard- pressed to damage anything but the input
shaft of the transmission, and even then, it'd happen soon after installation
if it was going to do it.

hope that helps,
t