How to lock the gearbox?
Turbo Mini Forums

I need to take off my first motion shaft bearing and gear, so need to lock the first motion shaft.


Haynes simply says select first and top gear. I have no idea how to do this.
Can someone explain how to lock the gearbox so I can finish it please?

Turbo parts collector at the moment, almost ready.

Remove the diff side plate on the right hand side.

The "ear" on the plate holds in the ball and spring which is the detent on the selector mechanism.

But the ball/spring are inside a small steel tube....

That tube is the interlock for the gears.

Pull that tube out and you can select any number of gears at once.

Putting it back is fiddly and you must renew the "O" ring behind the "ear" on the side plate or you will piss oil everywhere.

Schrödinger's cat - so which one am I ???

You need to twist the gear selector left and all the way over.

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


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Cheers, did that got it locked. Did the 1st motion shaft nut, but then it was stuck in what ever gears it was, and fiddling with it I managed too shoot ballbearings and springs across the workshop. I'll try again tomorrow on a new gearbox.

Turbo parts collector at the moment, almost ready.

Bad luck...

What was most likely causing it to be "stuck" was the selector hadn't stayed swung all the way out (sorry, I missed that step, luckily Mike added it) but had swung inbetween one or more of the selector rod slots.

The other tricky bit when trying to re-engage the interlock is that although the two main selector hubs have their own detent balls/springs (or rather they did have :) ), the reverse gear doesn't so its selector shaft can slide anywhere while the interlock is out. I usually end up pushing it backwards and forwards with a screwdriver whilst rotating the selector shaft to "feel" when the slot is in the right place.

If you find all the balls/springs (highly unlikely, you will probably end up buying some new ones...) you may just about be able to re-assemble it in the gearbox using a wide cable tie like a piston ring compressor, but the cable tie being flexible enough that you could slide it over the three holes one at a time. Fill the holes with gease first, it stops the springs from flying quite so far and helps hold the ball while you push it down and slide the tie over it.

Best of luck.

Schrödinger's cat - so which one am I ???