I have a 54 plate Mazda 6 with aound 85,000 miles on the clock.

The car has started jumping out of 5th gear when I accelarate. All other gears our fine, and desperatly want to avoid replacing the whole gear box.

Has anybody got any sugestions on what the issue may be?

Not very mechanically mind, so laymans terms only please!

 

If you haven't changed your fluids (tranny and clutch), now is the time!

 

Change the transmission fluid. It might help. I don't think the clutch hydraulics has anything to do with this. In my 98 protege the clutch hydraulics are being fed from the brake fluid reservoir. When you have the brakesystem flushed make sure they take care of the clutch as well.
There may be other reasons for the gear to pop out:
Worn synchronizer ring. If that is the case the transmission has to be removed and opened to replace the synchros. That is labor intensive.
Worn bushings in the shift linkage: If your shifter feels a bit too wobbly or mushy worn bushings could be the reason. With the car on the lift it should be easy to observe the how the linkage acts.
Bad motor mounts or transmission mounts. These are rubber mounts that allow the engine to vibrate and shake a bit, but not too much. If they now allow too much movement they may tug on the shift linkage and cause the dropped gear.

Those are the things that came to mind. I hope it is not the synchro rings.

 

Try driving it in the conditions when in 5th gear, but in 4th. Does it doe the same?

 

What year car? My 3 jumps out of reverse on acceleration, I have to hold it in to keep it in reverse.

 

Any news on the out come of this? I have a Mazda MPV (based on Mazda 6 running gear) and I have the same problem.
It is dropping out of 5th gear after a long drive on the motorway. All other gears are OK and on short journeys 5th gear is fine. Thanks

 

See my post here on the shift-fork and "false positive" on the gear oil replacement:

https://www.mazdaforum.com/forum/maz...neutral-19244/