Series 3 Rumble on part throttle

Having run Harry round for a few miles now it's clear there is a strong rumble coming from under the driver area on part throttle. No rumble on no-throttle or above 50% throttle upward. There is also a terrible rumble using 4wd.

I'm fairly confident of a transfer box front output bearing on the way out, but is there a way to confirm? Also any links to good how-to's? Looks like a fairly straight forward job to replace, I just need a slide hammer and get an adapter knocked up.

The part numbers I've found for the job are:

Seal - FRC1870
Bearing - 217325
Felt washer - FRC6461

I'll probably get the bearing from a local bearing specialist. I've found a universal bearing number RLS10, can anyone confirm thats correct?

In the long run I would like a high ratio conversion from Ashcroft to go with a recon of the main box (1st is a bit tough to get into and the shift between 3 &4 needs double clutch) but for the moment I think just a bearing to quieten down the rumble!

Thanks all.

You will need to remove the gearbox or transfer case to change that bearing.
Part numbers in this fikle attached.

Hi @Blackburn sorry I didn't see your reply!

Thanks disappointing. Looks like it might just have to wait for a full gearbox rebuild. Think I might treat him to a high ratio conversation too (budget depending!)