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MG Midget and Sprite Technical - 1st Gear stuck..and gearbox leaks

At Le mans this weekend my midget stuck in 1st gear - actually in heavy traffic heading onto the exit from the dual carriageway heading to Saint Saturnin.

Search the archives and found discussion of 1st gear moving too far and allowing some ball bearings to pop up and block the selector fork. Seems to match my issue exactly - I couldn't drive anywhere because of the traffic but we jacked the rear up and by starting reving/braking managed to unstick it which seems to correlate with the other threads.

Any other suggestions of how to verify and/or prevent without removing the whole thing ?

Whilst poking around at the gearbox noticed the gearbox oil was very low and lots of gearbox oil underneath. I assume its leaked from the rear - what sort of seal is this and is it prone to leakage ?

I dont know the complete history of the gearbox but it hasnt been stripped in my 70K miles and 20 years of ownership. I strongly suspect its original on 170K miles total so possibly due a rebuild. How much can I rebuild myself or is re-con the way to go ?
Dean Smith ('73 RWA)

http://www.spritespot.com/gallery/toomanyspridgets/first_good

http://www.spritespot.com/gallery/toomanyspridgets/first_jammed

Best tip seems to be to drill and tap a thread so you can wind in an adjuster screw that keeps the selector fork from going back too far.
Another option is to somehow fit a spacer on the selector shaft to keep it from going right to the back of the casing.
r thomas

Its a known issue with A series boxes - the 1st/2nd selector ring goes too far and the detent ball bearings trap it in 1st - it comes out with force sometimes... It is likely that now it has started doing it it will do it again (at an inconvenient time). I can't see how it can be fixed without removing the box.

The rear gearbox seal is easily replaced with the gearbox removed - impossible with it in place I would say...

I build my own gearboxes, but unless you're desperate to do so and have a reasonable mechanical ability I would suggest you get someone else to rebuild your gearbox. They can be tricky to get right.

JB
James Bilsland

The boxes are reasonably easy to rebuild and you don't need IMHO special tools.The Haynes manual is very helpful and easier to follow than the official BL one. Replacing ALL bearings and rear oil seal does the trick in most cases. The excessive movement of first gear is often down to worn bearings and missing main bearing shims causing too much lateral movement of the third motion shaft. Try to avoid dismantling the selector dogs as the little ball bearings can fly out and are a pain to put back!

If you don't fancy it then a re-con will be ok but they are also mainly reycled bits now anyway.

Bob Beaumont

There is a mod which I do in order to stop it doing it again. It doesn't involve removing the gearbox, just the side cover.

I don't think I have a photo of it on my laptop, so I'll have to look on my PC when I get home.

If it's been driven much with it stuck in first, it can cause some very rapid wear of second gear synchro...don't ask me how I know!

When rebuilding, it is also a good idea to replace synchro rings and check selector forks for wear. A worn 1st/2nd fork could have caused your problem
Dave O'Neill2

Some years ago I went through this issue. I put up with it for quite a while as when it happened I resorted to the accelerate - brake and pull very hard on the lever to get it out of gear. Always worked, although never convenient! Never tried jacking the wheels up to do this, just found a quiet bit of road.

Whilst "putting up with it" I discovered that it was prone to happen if I was trickling forward in 1st - as in slow moving traffic - whilst lazily resting my hand on the gear lever (bad habit!). This would induce it to stick in 1st. Once I worked that out I found I could stop it happening by modifying my driving, getting into 2nd immediately in slow traffic and letting go of the gearlever! I only then bothered to fix the problem some while later when I had the engine out anyway. (added a copper washer on selector shaft)

So, if this is the first time it has happened, my advice would be to live with it until you have other reason to remove the box.

Guy Weller

Right, I've found the photos.

Basicly, it's a piece of 2mm steel bent to a right-angle, slotted to fit over the selector shaft and with a hole drilled in order to mount it on the fork with the securing screw and locknut.


Dave O'Neill2

It needs to fit snugly up against the side of the fork. It is actually fitted so that it goes between the 1st/2nd fork and the back of the casing, to limit rearward movement. If it is thicker than 2mm it may not fully engage first gear.

I have used this mod on several gearboxes.

The one in the photo is a spare that I made up and I mocked up to take the photo, although I seem to recall I used a 3rd/4th fork at the time.

Although it was a spare, I can't seem to find it now!


Dave O'Neill2

Dave, that is smart thinking.
When I fixed mine I put a copper washer on the shaft in that same position. But to do so I needed to remove the engine, remove the gearbox and then part dismantle the gearbox, all just to fit a washer! Your little L-shaped bracket simply inserted through the inspection cover and secured by the selector set screw is a much easier solution!
Guy Weller

Dave, that's brilliant. When it happened to me, I took the bos out on a building site on Crete, to fix it. Now I've gone type 9, but still worth knowing.
Lawrence Slater

Great - Thanks for the comments and advice.

Pictures are great -thanks Dave especially for those :-)

I was indeed crawling in traffic - quite possibly stretching in the sun aswell so may well have pushed on the gear lever more than normal. When I first got the car (1990-ish) we thought the gearbox wouldnt last long....so 20 years is well above expectation. If that little mod can get me another few years all the better :-)

And my mates spent the rest of the weekend telling me it was all my fault because of the low gearbox oil ;-)
Dean Smith ('73 RWA)

The last time it happened to me, it was also at Le Mans.

I had only just arrived, after a long journey. I unloaded the car off the trailer and drove it to scrutineering. When I drove it back to the paddock, it was stuck in first. I dried driving it around, on and off the power and pulling on the gearlever, but to no avail.

The harder you pull on the lever, the more it forces the inner hub and second gear synchro ring onto second gear, hence the rapid wear.

I had to pull the side cover off and then push the inner hub towards the back of the car while pulling the selector fork forwards. After that, it was crunching into second gear. When I got home, I pulled the 'box apart and replaced the synchro ring, but it still crunched until eventually it started jumping out of gear and I had to fit a replacement gear.

What I forgot to mention is that you have to be careful not to move the selector fork on the shaft while fitting the mod.
Dave O'Neill2

"be careful not to move the selector fork on the shaft"
True, but on my box the set screws have pointed ends that locate in depressions on the shafts, so locate and fixed the positions of the selector forks. Maybe they are not all like that though.
Guy Weller

Guy

Yes, they are all like that, but when working on the 'box in the car, things aren't always so easy ;o)
Dave O'Neill2

but I'm guessing I need to move the fork to find out if I've got depressions to re-locate it accurately. Be a while before I can have a good look but will certainly be doing that mod I feel.
Dean Smith ('73 RWA)

No, just make sure it doesn't move and it should be fine.

The other thing I didn't mention - although it's fairly obvious - is that you need to back off the locknut to allow for the thickness of the bracket, or the screw won't locate in the recess.
Dave O'Neill2

This thread was discussed on 19/06/2012

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