Why rebuild the original 100,000 mile Moss gearbox?
Eliminate jamming in first gear
Eliminate never-ceasing oil leak from rear of gearbox

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There were two significant faults in the Moss gearbox that needed attention:

1. The gearbox would intermittently become stuck in first gear, if the car was rolled to a stop in first gear. If the car was angle parked against a kerb gutter, and stuck in first gear, a rear wheel had to be jacked up to free the first gear.

2. The gearbox was leaking a lot of oil from where the layshaft and the reverse gear spindle exited the alloy rear extension between the gearbox case and the overdrive. These two shafts are below the oil level and the leak occurs whether the car is being used or not. Making it worse, any use of the car spread the leaking oil over the rear underside of the car.

Jamming in first gear

Leak from rear alloy extension

Other tips for gearbox rebuilding

Apart from these two faults, and of course the inevitable weak synchromesh on second and third gears, the gearbox and overdrive was otherwise in near-perfect condition, based on having driven the car for 2000 miles since purchase. I also had receipts from the 1998-99 restoration that showed new bearings and seals had been fitted to the gearbox at that time. In short, the gearbox was quiet, and the overdrive worked perfectly.

While I could live with the oil leak, the first gear problem had to be fixed, even though it meant that the engine and gearbox had to be removed from the car to eliminate the problem. Some internet searching led me to the cause of the problem, so it was a case of a lot of time and effort to fix, but not a lot of cash, assuming I did the work myself.

Along the way, however, I was tempted by the Tremec T5 five speed gearbox conversion kit available for the XK150, and the delights of first gear synchro. I live in a hilly area of Sydney, where the lack of first gear synchro makes things more difficult when I drive my XK in normal (impatient) traffic, rather than just using the car on special occasions.

Eventually, I decided to remove the Moss box, temporarily (for how long??) replace it with a new T5 gearbox, and rebuild the Moss gearbox at my leisure. As it turned out, the T5 conversion took ten weeks from March–May 2015, with the help of a friend who also owns an XK140 and an XK150.

The rebuilding of the Moss gearbox took eight weeks, from August-October.














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