'91 MK3 2.5D MT75 Transmission Noise

[tmmn]

Hello all,

As the title suggests, we have a 2.5D MK3 Transit from the year 1991 (MT75 Gearbox). We bought is a project and it sure delivered on being a project, but that's fine.
I think some background information on the problem might be useful so bear with me. (short version at the bottom)

We bought the van knowing there was some noise coming from the clutch/transmission in neutral and clutch engaged, we initially thought it was a bad throwout/clutch release bearing.
So we pulled the transmission and clutch, replaced the spigot bearing, rear main seal, whole clutch assembly (including throwout bearing). Put some fresh gearbox oil in and put it back together.
However when we had everything removed we noticed a crack in the rear main seal housing, but we couldn't get a replacement fast, so we put it together knowing everything would have to come off again. Furthermore, the release bearing guide sleeve was the aluminum type and it was clearly worn.
The noise got a lot better, but over time it would slightly come back again, also it developed a clutch judder. This was not a real surprise since the crack in the rear main seal housing would cause oil to leak near the flywheel.
Months later we got the time to get it on the lift to replace the rear main seal housing, release bearing guide sleeve and we decided it would be wise to replace the clutch again since there was a good chance it was now bad from the oil spillage. After replacing everything the clutch engages smooth and it drives really well. However, the noise coming from the transmission now seems worse or as bad when we just got the van.

A clear description of the noise:
- When in neutral gear, and the clutch pedal depressed (clutch unengaged), there is no noise whatsoever (indication that we had it all backwards when diagnosing a bad throwout bearing).
- When in neutral gear, clutch not depressed (clutch engaged), there is a rattling/knocking/clunking noise (maybe a bit like a machine gun?)
- The noise is not so obvious when the engine is cold, but when warm the noise is pretty loud.
- The noise disappears with higher throttle/speed
- Noise somewhat present when in gear but not clearly distinguishable due to engine/road noise.
- Noise still present when clutch cable is removed from clutch release arm (so it's not the release bearing rattling against pressure plate)

Here you can find an audio recording of the noise: https://youtu.be/Nbjna1DmB_E

We're thinking it might be a bad input shaft bearing, but my experience with bad bearings (on the farm) is that they're more likely to produce screeching noises when bad.

If you have any suggestions, don't hesitate to share them. All the help is much appreciated!

TL;DR
Noise from transmission in neutral and clutch engaged, replaced clutch assembly and spigot bearing, noise got slightly better. Replaced clutch again due to oil leak, noise came back.

[V184]

Low lift clutch normally eliminates that noise

[tmmn]

Thanks for the reply. Have to be honest, didn't even know there were low-lift and standard-lift clutches.
Maybe being cheap was an expensive mistake then, we fitted an aftermarket 'Statim' clutch set (6 springs) that seemed ok. Then the second time after the oil leak we fitted a 'Nexus' clutch set (4 springs) and the noise is terrible.
I can't seem to find any specifications on the clutches being low-lift, so what aftermarket clutch would be our best bet?
I've read Sachs and LUK clutches are supposed to be of high quality.

[V184]

Thanks for the reply. Have to be honest, didn't even know there were low-lift and standard-lift clutches.
Maybe being cheap was an expensive mistake then, we fitted an aftermarket 'Statim' clutch set (6 springs) that seemed ok. Then the second time after the oil leak we fitted a 'Nexus' clutch set (4 springs) and the noise is terrible.
I can't seem to find any specifications on the clutches being low-lift, so what aftermarket clutch would be our best bet?
I've read Sachs and LUK clutches are supposed to be of high quality.

Factory fit was Sachs, go for a later say 1997 model type

[tmmn]

Brilliant, thanks for the help