reverse switch-lights. Gearbox gurus

[diabolov]

Morning all,

Hope you are all safe and well. Got a slight problem that was pointed out to me by a classic mini driver at a set of lights, and that is my reverse lights
flicker on and off. I got under the van and the wiring looks sound so I tested the switch and that works as in it makes and breaks connection. The issue seems to come via the gear selector. I had a multi meter across the switch and as I push/pull on the gear selector, the switch makes contact a lot. So I went through the gears and the reverse light comes on in reverse but also in 4th and it seems, via my son shouting from the back of the van on-off-on-on-off-on-off-on, as i moved the gear stick about too.

I had replaced the clutch a few weeks back but that went smoothly enough. No major issues, so I can't see anything that could cause a problem there...the fault was pointed out after that but that could be coincidence and the fault could of been there before.

I've disconnected the wire for the moment.

SO in your experiences is this a common switch problem and a replacement would be enough or is this a little deeper? what's behind the ''cone'' the the switch is screwed into? Is it just a bearing housing for the selector arm? can I remove that without anything nasty dropping out or worse down into the box? I see that Brickwerks do a gasket for the cone but I can't find much else regarding behind the cone...

Thanks all

M

[Mocki]

Simply add a thin washer to the reverse light switch so it screws on a fraction less . To the actual switch where it screws onto the housing , increasing its height and decreasing its depth

[diabolov]

OK Mocki, thanks. I take from that, the suggestion is wear in the switch increases it's length causing more contact points.

M

[Aidan]

The selector shaft that the linkage connects to runs across the gearbox and the end of it has a pressed metal sleeve on it with a raised section that operates the reverse switch. There should be an alloy washer under the reverse switch.
The selector shaft runs very close to the mainshaft of the gearbox and sometimes comes into contact with it when there is a lot of wear in the bearings as in 4th gear the load effectively pushes the gears apart, so the selector shaft is pushed up by the mainshaft on and off load, light goes on and off.
The selector shaft also has a pressed metal pivot cup (under the big spring when you remove the reverse switch housing) which wears on the shaft and in the bore of the case allowing the end of the shaft to move up and down, and also is quite often broken, so not a tight fit on the shaft also allowing vertical movement, translating force from the ball end to the reverse switch end.
As you only need 0.5mm-1.0mm of engagement of the switch to make contact it doesn't take much play in anything or force other than the normal force acting on the shaft to make contact with the reverse switch.
The shaft is not repairable, many people have tried to 'fix' them and bodge them, usually without success, and lots of 'rebuilt' boxes have damaged components refitted as they are repaired to a cost rather than to a quality and many of them have been repaired several times cycling through the hands of the exchange box suppliers who used to be able to get them for £50 each from the scrap merchants and then do the absolute minimum to them and accept a 1 in 30 warranty claim margin as part of the business model.
Selector shaft can be replaced insitu if you are careful, and once extracted will show if there is contact with mainshaft or if the cup is broken, but if the cause is wear allowing contact between the mainshaft and selector shaft that is rebuild time.

[diabolov]

Thanks Aidan....plenty there to read through and go check on..

When you say ''Selector shaft can be replaced insitu if you are careful'' what are the pit falls of removing it for a looksee ?

M

[Aidan]

visual access is poor so you are relying on feel, some force may be necessary especially on removal and wiggle on refitting, basically you are threading the cage on the shaft through an aperture (the rely lever) and two selector fork slots, a nylon bush and a seal

[diabolov]

Thanks again Aidan, appreciate the help.

Regards

Mark