dazdavies

iTrader: (22)

I have a UK classic circa 400bhp with a UK 6 speed gearbox fitted.

The gear change into fourth has always been a tad notchy but never any problem. However this morning the car jumped out of fourth a couple of times.
By this evening the car will stay in fourth for a few seconds and jump straight out. Now fourth is completely unusable as soon as i change into it it jumps straight out unless i physically hold it in fourth. All other gears are fine with no problems at all

Any ideas of the problem and roughly how much to fix. After all the mods I have had done lately the money pot is a tad on the low side to say the least.

Gear Oil level is OK and only changed about 3000 miles ago

Any help appreciated.

sponners

iTrader: (4)

Hi, sounds like it could just be linkage adjustment/alignment!

jaytc2003

iTrader: (1)

Does the box have standard internals?
If so, I would say that 400bhp is just a bit to much for standard internals to cope with.

dazdavies

iTrader: (22)

6 speeds can cope with 600bhp plus. Its not the power thats the problem otherwise the other gears, particularly second and third would be showing problems and their not.

john banks

I had the same with 5th gear on a new UK 6MT running 430/400+ for 23000 miles with a bit of drag racing. It was the plastic coating on the end of the selector fork that was worn. It needed a new selector fork and 5th gear because the dog ring on that gear was also worn. Whlist there I changed 3-6 synchros and all the other selector forks. Gear teeth were OK. Cost was about £1100, but a bit more was done than needed to be because the box was out. The plastic on the selector fork could be replaced by bronze for strength and more noise.

Apparently the new 6 speeds have carbon sintered selector forks for a smooth change in the upper gears.