Whining after crossmember change?

Hello everyone

i have just changed the (rather wrecked) gearbox crossmember on my 300tdi and now notice a whine / vibration through the floor plates coming from front.

is this a co-incidence? Recent (week) change of fluids in transfer box / diffs / swivel and greased UJs. Or is it possible I’ve disturbed something and affected geometry? The crossmember went back exactly as the other, and mounting rubbers appeared fine.
Vehicle is an ex 19J with 300tdi/r380 with LT77 tunnel.
Any steers appreciated. I’ve rechecked all points but can’t see anything obvious. Calling on collective knowledge - thanks

Should have added -
Can feel it through feet and it disappears once idling and when mobile disappears once accelerator is released (like downhill). Also slightly intermittent - like a pulsing hum

Could anything be touching the gearbox? I had a bit of noise after fitting a reconditioned gearbox last year which I traced to the top of the box fouling the tunnel. A bit of flexing and repositioning of the screws holding the tunnel down seems to have quietened things a good deal.

The new gearbox has a little song in its heart, but nowhere near as bad as the one I replaced. Now it's done around 12,000 miles it's quietening down too.

Thanks for reply - I’ll have another look but had floor plates out in frustration to check I hadn’t raised it and ‘interfered’. Will revisit in daylight, then if no joy I’ll do the diff lock on/ props off to see if I can isolate the noise further.

Brown said:

Could anything be touching the gearbox? I had a bit of noise after fitting a reconditioned gearbox last year which I traced to the top of the box fouling the tunnel. A bit of flexing and repositioning of the screws holding the tunnel down seems to have quietened things a good deal.

The new gearbox has a little song in its heart, but nowhere near as bad as the one I replaced. Now it's done around 12,000 miles it's quietening down too.

Click to expand...

Hi

So, after digging around the seat box - turns out previous owner never changed the LT77 tunnel to accommodate the R380 box. So front of seatbox was touching the top of the transfer box! Slightly annoyed I didn’t check this earlier as now need to fork out for new tunnel, diaphragms at both ends and R380 floor plates (made worse by fact I had replaced floor plates a couple of months back)! Why the crossmember change made it more audible I’ll never know!

On the plus side I’ve solved a few other issues round handbrake, propshafts and rear diff as part of the investigation!

Thanks for the steer

Murdo