A loud screeching and rattling is coming from my drivetrain. Series 3 1980.

A loud screeching and rattling is coming from my drivetrain. Series 3 1980. Here's a puzzler, there's an intermittent, very loud screeching and rattling, accompanied by a low rumbling sound, coming from my drive train. It only happens when I'm driving, so I can't listen to pinpoint the sound. I don't think the gearbox is the problem as I can select all the gears fine. The noise stops when the clutch is depressed, and it seems to be worst when I'm accelerating through second and third. It sounds a bit like something loose in the bell housing or clutch. The prop shaft UJs seem to be ok. Someone suggested it might be build-up of old, dirty oil in the hand brake drum, but I don't think this is the problem. Has anyone come across anything like this? It's a 1980 Series 3 by the way.

Take off the handbrake drum - just to check there's not a broken spring ...

Also look for play in the prop UJs ...

The UJs seem fairly solid. I'll check the hand brake tomorrow.

Sounds like possibly something around the clutch if it's worst when accelerating and stops when clutch is depressed.
If oil was building up in the handbrake drum I'd have thought you'd notice the handbrake failing to work (that was my experience anyway - common problem with seals that are supposed to keep the oil from getting out of the transfer box)
If it's not a failing clutch then I guess it could be a bearing somewhere around the clutch/gearbox area.
Does it occur in all gears or only 2nd and 3rd?
Have you checked gearbox by putting transfer box into neutral and shifting through the gears with the engine running. All you should hear is gears whirring away normally with no screeching.
If screeching ceases when you're in motion and you depress the clutch so the vehicle is freewheeling then that suggests to me that the majority of the drivetrain (gearbox/transfer box/propshafts axles etc) is OK as all that stuff is continuing to turn (although with different loadings)

It's not the handbrake. And someone I spoke to on the phone says it can't be clutch bearings as they would most likely only screech like that while it was depressed. I tried the gearbox with the transfer lever in neutral, it rumbles and rattles a bit more than it should, but no screeching. It's only happening when the engine is under load, in 1st 2nd and 3rd, (I've not really tried it for long in 4th because I don't want to risk that long a test run). Are there any bearings in the gearbox that would do this, but still allow me to select gears like normal? Is my gearbox shagged?

Are you low on oil ?

Mainshaft would rumble I presume as could layshaft ? Anything with a bearing has the ability to make noise but JM is your man for that kind of stuff

Drop gearbox oil and sieve for anything lumpy.

When going through the gears with t/box in neutral, did the gearbox go quieter in 4th? If so it may that the layshaft bearing are u/s. if it sounds the same could be mainshaft bearings.

Rear mainshaft bearing housing can also spin in the box (it was on mine). Don't know if this could cause screeching though but bearing failure would not interfer with selection (unless they actually broke up)

There's definitely oil in there.

It makes the same sound whatever gear I'm in, so maybe it's the mainshaft bearings. I was just thinking of straining the oil, but it'll have to wait till tomorrow night now.

I'm wondering if the spiggot bush would cause this if is was worn or broken. I'm sure I've heard of similar symptoms before.

It's official. The main bearings in the gearbox are knackered. We're going to try fitting a series 2 box, so I may have to start a new thread...
Thanks everybody.