Sounds like a big rattling noise at idle? Disappears when clutch depressed? Disappears when revved up in neutral?
If this is what's happening, it's a normal gearbox noise, caused by the engine "power pulses" at idle. These vehicles spent hours at idle when in service, and the noise is the input gear rattling against the cluster gear causing a tiny bit of wear. It's classic diesel gearbox rattle. They overcome this rattle in more modern diesel powered vehicles, by fitting a dual mass dampened flywheel. It dampens the power pulses at idle common with most, if not all, diesel engines. It's an annoying noise, but its normal with older design gearboxes. Don't forget, this LT95 gearbox has been around, unchanged, since the early 60's.
Cheers.
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