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1995 XJR. After an overtake using the J gate manual side then leaving the lever down on the left hand corner for the next usage, the dashboard G/Box warning light came on. Car seemed to be driving fine and no issue with gearchanges.

Then I got into city driving and found that moving off and getting into higher gears were of the " wait, thump" variety. Open road no problem. Gearbox oil up to level and looking nice with no burnt smell.

I left the car parked up for a couple of days whilst away for the weekend. On return, light still showing but gearbox seems to change as always, no thumps , no hesitation.

Any Ideas? Can I reset the light? Thanks.

Ok, here we go then, what mileage is on the car and what evidence of any oil changes??

I would suggest an oil and filter change as a first port of call, will improve the change quality no end, while the car is in the air, locate the connector where the loom goes into the box, disconnect, clean with electrical contact cleaner and replace, then disconnect the battery for 30 mins, this will dump all the fault codes and reset to zero

test drive and see if the light comes back on

if it does, the fault is likely to be the transmission control module going awol, cheap and easy to swap out, OR a change solenoid failing, not cheap and easy!!

hope this helps