You should get underneath and try to verify which parts are worn out, or even just not done up properly but..
Retainer cap and bush for shaft 540440 is possible culprit
gearlever 549219 acorn on end gone ?
spherical seat -rubber base for lever 539685 common problem
Selector peg at front of shaft 539627 should have some rubber on end?
rubbers at front of tie bracket 556436, 556437
Get a parts book - P6 club ?
Last time I pulled a 2000 box This is roughly how, IIRC?
- remove engine stay at front, and fan
- disconnect radiator hoses
- remove engine mount vertical bolts, replace with long screwdrivers
- remove prop shaft.
- remove tunnel finisher and gear lever
- remove front exhaust pipe so engine can tilt back
- disconnect speedo cable, reverse light wires
- disconnect clutch slave, tie aside
- check if heater hoses, throttle connection need disconnecting
.
.
tilt engine backwards just enought to access all bellhousing bolts, and slide the box out.