Morris Minor Owners Club

The reverse selector plunger: how does it work? I presume it's purpose is to stop accidentally selecting reverse, but I have not been able to work out how, apart from suppling a slight resistance before selection.

That's it!

If you pull the gearlever over to the right to start the reverse gear selection, but before actually pulling lever into reverse, does it spring back to centre, if you let go?

Yes indeed - that's what's intended.

Well mine doesn't!

Ah well - something missing! I think it's in the remote control - just under where the lever goes in although many moons since i worked on a gearbox. If you take the rubber boot off you should see how it works.

When I got my rebuilt gearbox, water had got into the hole where the gearstick normally goes, and the detent plunger had rusted and seized. If you take the gearbox cover off and remove the remote control unit, you'll find a little access panel on the bottom. Open it up, and you see this inside:



The one on the left is the one that had seized. On the back of the remote control unit is a bolt that holds in a spring-loaded ball bearing that provides the detent action. From the diagram in the manual, it appears there is also a small pin drifted into the side of the casing that prevents the plunger falling out. You probably need to get that pin out to clean up the plunger and get it moving again. I just fitted the working remote control unit from my old box instead.

Thanks for the clear picture and explanation. I have recently rebuilt the box after a complete stripdown and all the bits you describe are present and clean greased and working perfectly. My first concerns were raised when I screwed home the bolt that holds the spring loaded ball bearing; I could not select reverse! If I backed off this bolt aprroximately one eighth of an inch all is ok, but as this is not normally done I wondered if the detent action was now not functioning as it was designed to do, and consequently allowing reverse to be selected when not intended.

I see; it does sound like there is a problem with the detent to me.

I wonder if the plunger could be the wrong way round, so the detent ball is pressing against the wrong part?

I've checked that out, in fact I can see the detent when looking through the hole that the bolt screws into, although I must admit when the plunger moves upward( when the gearlever is pulled to the right) the detent is still partially visible, whereas I would have thought that it would have disappeared to reveal more than just a part of plain plunger, in fact it did occur to me that as the detent was still partially visible the ball bearing was not being cleared properly unless spring tension was relaxed, by this slackening off of the bolt.
Alex if you ran your box with the siezed plunger what were the symptoms?

The plunger was stuck all the way in, so there was no resistance to selecting reverse.

One more thing, did it seem more likely to select reverse by mistake, especially when going into 4th ( that's my worry)

I would say it would - better to get it sorted out.

better to get it sorted out.

Is there a problem?

There will be if you whang it into reverse by mistake while travelling forwards!

If there is no problem though, that will not happen. as it seems the only difference between my gearbox and yours is the thickness of washers, I'm trying to decide if this constitutes a problem, without much luck!

As long as you are careful! Just make sure the box can't select two gears at the same time (catastrophe!) - ie is the interlock system definitely working ok?

les wrote:One more thing, did it seem more likely to select reverse by mistake, especially when going into 4th ( that's my worry)

Probably. I noticed and fixed the problem before I put the cover back on.

les wrote:If there is no problem though, that will not happen. as it seems the only difference between my gearbox and yours is the thickness of washers, I'm trying to decide if this constitutes a problem, without much luck!

I don't understand what you mean about washers. The spring-loaded plunger is there so you can feel when you have pushed the stick past the 3rd/4th position to the reverse position. If it's not working then you might accidentally hit reverse when trying to change up to 4th - ouch!

Earlier I mentioned that to get the lever into reverse the spring loaded bolt had to be backed off one eighth of an inch from fully tight, the washer is used to pack out to this dimension ie one eighth inch thick copper washer. When this is done I have a fully functioning gearbox. if I use the original thin washer I can't select reverse gear. I have just been wondering whether this will present a problem as strictly speaking the bolt should only need the thin washer,