Gearbox trouble

[Stixbnr32]

Hey guys - So I had issues with my gearbox coming out of 4th gear off throttle.

My mechanic looked at the joint from the shitter into the gearbox and we replaced it anyway but no change.  Then my tuner actually took it apart as he noticed the boot at the bottom of the shifter was gone so that made these quiet again and also stopped some fluid spilling over the top.  He also noticed that the shifter had some parts install wrong and fixed this (grrrr at my mechanic).

This fixed the 4th gear pop out issue but then I was driving along and off throttle again and 5th gear popped out which it has NEVER done.

Now im just confused as to why its changed from 4th to 5th with a correctly installed shifter.  Any ideas?

[Robocop2310]

Open up your shifter enclosure and check the shifting pattern. 

Did you install some sort of shorter shifter kit?

[GTSBoy]

Either an engine or gearbox mount is sufficiently stuffed to have had the whole driveline move such that the shift lever is getting pushed by the side of the tunnel hole, or, there is a problem with the selectors.  You might have lost a dowel or pin that holds the selector onto the shift rod.  Might be only partway out and wobbly.

I'm sure there are other possibilities too, but failing to imagine them right now.

[Dose Pipe Sutututu]

Has the gearbox ever been overhauled?

Many things could contribute to this, from worn bearings to worn synchros, etc.

Something simple, try flushing the box and popping in fresh fluid. If the box is pretty much on it's way out, then potentially use Redline Shookproof to mask up the problem and drive it till the box goes bang.

(That's what I'm doing).

[Stixbnr32]

Yeh the box has been overhauled once before (5 years ago).  I was thinking of doing a fluid change but didnt think that will make a difference to it popping out of gear off boost.

I may have an opportunity to get a gearbox (no transferase or shifter which I dont need) for cheap.  Then when this one is out I can rebuild with stronger.