Strange noise

[x_atlas0]

Hello everyone.

I have a strange noise that I can't place, especially with the behaviour required to induce it.

When accelerating, at around 3k-4k RPMs, there is a very loud, RPM-dependent, gear independent, somewhat grinding noise. It seems to be coming from the transmission or further back. The noise is not present when coasting at any speed, revving with the clutch in, or revving when the transmission is in neutral and the clutch is out. The noise abates at around 4k and does not return, even towards redline.

Any suggestions?

 

[Malc]

Could be
1)..Gearbox mount soft/breaking up
2)..Bearings in the box worn/breaking up
3)..Gilbo (Rubber donut on the back of box to propshaft) going
4)..Propshaft UJs or centre bearing
5)..Clutch

If you can get your car up on a lift and check about, pull push propshaft about, waggle gearbox etc. If nothing obvious then it is probably inside the gearbox

Malc

 

[x_atlas0]

Could be
1)..Gearbox mount soft/breaking up
2)..Bearings in the box worn/breaking up
3)..Gilbo (Rubber donut on the back of box to propshaft) going
4)..Propshaft UJs or centre bearing
5)..Clutch

If you can get your car up on a lift and check about, pull push propshaft about, waggle gearbox etc. If nothing obvious then it is probably inside the gearbox

Malc

1. Mount new when I did a 5 speed conversion less than 500 miles ago.
2. Possibility
3. New guibo with 5 speed swap
4. Driveshaft rebuilt, but not E9 driveshaft. Getting that "fixed" again (freaking DS shop tried to pull a fast one and didn't give me my original DS, they gave me one they rebuilt from an E12)
5. Checked clutch when doing 5 speed swap; could still read the making paint on the face; it was new too.

I guess that means it is most likely the trans or the DS. Although, if it was the DS, would it not be more speed, rather than RPM, dependent?

 

[Malc]

New or rebuilt 5-speed box?

DS might be problem especially when torque is applied (accelerating) was it balanced properly? could of lost balancing weights??
Malc

 

[x_atlas0]

New or rebuilt 5-speed box?

DS might be problem especially when torque is applied (accelerating) was it balanced properly? could of lost balancing weights??
Malc

Very, very used. It may also be low on fluid. When payday rolls around, I plan to do a diff and trans fluid change with redline or royal purple fluids; it will hopefully help. The trans is from an 81 528. I think the trans has been rebuilt sometime, as the thing still shifts great, synchros and all.