Strange gear/clutch noise between 1000-1500rpm (diesel)
 

Hi all,
My diesel 940 is generally driving very well now I’ve taken care of most of the mechanical odds and sods on my to-do list.

However, I have a persistent noise that seems to be coming from something in the transmission region. I initially thought it was just happening in first and second, but it’s just more noticeable in those gears due to less road noise being present to mask it-it appears to be happening in all gears.

It only happens when the car is warm. It’s not quite a grinding or chattering noise, more a low pitched roar. It’s audible inside and outside the car, but only between 1000 and 1500rpm, after which it disappears entirely.

The clutch drags a little unless the pedal is fully depressed to the floor, and can sometimes judder a little on takeoff. Although it drags, the point of full engagement is quite high. Both of those factors make me question whether the noise is clutch related.

I have changed the gearbox oil which has had no effect on the noise whatsoever-it was identical before and after changing the oil, which makes me think it may be more clutch related than gearbox, as I’d expect at least a slight change in tone or volume with fresh oil if it was a box issue.

Gear changes, clutch drag aside, are absolutely fine and there are no issues with driving. I’m keen to diagnose it though as the noise is bugging me!

Any and all advice very much appreciated as always 🙂

Phil

From your description Phil, it sounds as if the DMF could be getting weak, i think your car is on the changeover point as to whether it had a DMF or not but the diesel guys may tell us that they always had them or otherwise correct me if i'm wrong.

If you hold the clutch all the way in does it eventually go quiet or if you leave the clutch out does it change the noise at all?

Unless I’m much mistaken, I think the diesels have a dogdish solid flywheel, but this may be earlier cars-mine was MY1995 but registered in January 96.

If I dip the clutch when the noise is happening it instantly goes away-it also doesn’t happen when releasing the clutch as I pull away, only when the clutch is fully engaged. When in neutral and stationary, there is very little difference in noise when the clutch is in or out. Perhaps a hair more noise when the pedal is down but very little in the way of chatter etc. The noise only occurs when under load, not when the car is revved when in neutral.

Does your 95 not have an M90 gearbox like my petrol 95? In which case it would have a dual mass flywheel. DMFs are more common in diesels.

In the M90 reverse is to the right and towards the driver. M46/47 is the opposite.

Hi Tony, yes it’s an M90...I stand corrected! I must have been confused with the earlier Dervs. This is great info-now I know I have a DMF I will make that the first line of inquiry.

Its an early type DMF with a rubber type compound between the inner and outer parts to absorb the fluctuations. Does not give you as much play as the modern type with springs etc in them.