Sorry Roy, you should have added that it was converted to semi-automatic and the gear changes are done with the rear jacked up so not stationary as such.

The unloader valve could be very relevant to the problem as Philippe said whilst driving it back when we bought it back, it appeared to have stopped "unloading", so maybe a leak caused that?

However the light doesn't come on now except when selecting 4th and reverse. i have told Philippe to try and get under the gearbox and get someone to select different gears, so he can see and hear what is going on.

Thanks for all the suggestions I will pass them on.

My bus number (if any): RTL 960, RM 1585, RML 2667 and several RTs

I would suggest either leaking pipes from the ep block to the gears or leaking seals in the box. You can do a stationary test by getting pressue up, stop engine, set ignition on and select the appropriate gear. You will either hear the air leak if it's a leaking pipe or bubbles in the gearbox. Lift the floor trap up to hear properly what's happening or get someone to lie underneath.

Plastic pipes ahave a tendency to gto brittle after about 10 ears, metal pipes vibrate and leak round the olives.

My bus number (if any): RML2532

Thanks Roy, much appreciated.

My bus number (if any): RTL 960, RM 1585, RML 2667 and several RTs