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MG Midget and Sprite Technical - Gearbox problems Midget

Hi - I have problem which I believe is common with the 1275 midget - when deccelerating in second gear the car jumps out of gear. I'm sure that I've seen repair kits for this but I can't find anything on the thread searchs. Does anyone know what the parts are when they can be obtained and how easy is the repair. Is a 'box out job? I only ask as this box is a second hand silver seal unit which I bought on Ebay to replace my whiney old box. The replacement is better than the original but I would like to fix the problem if I can. Any advice greatfully received.... Thanks Alan
Alan Drain

Alan.

What you describe sounds like the mainshaft is moving back and forth in the box as the thrust loading changes under acceleration or deceleration.
Unfortunatly, there is no 'quick fix' for this and yes, I'm afraid it is indeed an engine and box out job.

Buying a S/H gearbox always carries a risk unless you can actally drive the car first before you buy the part.

I would strongly advise that you look at the gearbox now before too much further damage takes place, these boxes can be expensive to overhaul, but once done are usually fine.

I find when ever I overhaul one of these gearboxes, the usual suspects are knackered, Laygear, Layshaft, First gear Synchro rings and all bearings. If you do this overhaul yourself, be carefull where you buy the parts, cheap is most certainly NOT best!

Good luck,

Mark.
Mark Boldry

'First gear synchro rings' - Mark, am I being thick? isn't first non-synchro?
Nick

Indeed you are correct, first is non sychro. Sounds like 2nd gear synchro is failing. This will continue to get worse, unfortunately they never get better. The metal it is putting into the oil will only cause more wear in everything else. Fix it now, waiting can be nothing but more trouble, spelled $$$$.
Mike G

Nick, Mike, just a simple punctuation error, it should read:

"the usual suspects are knackered, Laygear, Layshaft, First gear, Synchro rings and all bearings."

Mark.
Mark Boldry

Hey mark,


Just curiuos...not a problem anymore but would love to know the damage,

In my ribcase I damaged the box in advertantly...2nd and 3rd gear sounds like a chain rattling around..3rd much worse so and would get louder the fast you drive....runs smooth and shifted well..just noisy...lucas oil additive quited it alot.

HOw I damaged it....

2 back to back situaations...1st the old steel clutch line sprung a leak under the heaterbox...while driving and couldnt get it out of gear while driving away from a stop sign and ended up brute forcing to get it out of gear...thus 2nd was noise from then on.
2weeks later same situation only failure with slave and was stuck in 3rd gear and forced it out agian and 3rd became noisey after that.

like I said after replacing intire clutch system with new,,,it shifted well, and ran smooth, never got metal shavings in oil, and ran much quiter when putting lucas oil additive into the T.box...just chain noise is the problem...

Any idea what got damaged, Id like to fix it for "Just in case situation" If I should ever have to dump my datsun tranny.

thanks
prop
Prop

Hi, I don't want to hijack this thread, but I was going to start a similar thread for my 1500 gearbox problem.
Basically when I down change from 3rd to 2nd it crunches if the engine revs are to high, would this be down to my style of driving or could there be a more sinister problem? Changing up through the gears is fine with no problems, also 4th down to 3rd is ok.

Thanks
Kevin
K Grice

Kevin.

Your problem sounds like a simple Synchro failure. The 1500 (or Marina) box is not a strong one either and probably would benefit from being 'freshened up', IE, new synchros and bearings etc. You'd be amazed how much better it'll feel once done.

Prop.

Not sure what your problem is / was, but it would, in my mind, be prudent to have it checked over. I think I would need to see or at least hear it to give a more detailed opinion.

Mark.
Mark Boldry

Mark,
Thanks for the advice, I assume this would involve the gearbox & engine coming out? Also can it be done by a novice or would it be better to get a garage to do it? Do you think I would cause any damage by continuing to drive it?

Kevin
K Grice

Mark- thanks.

I haven't ever taken a gearbox apart and all of those bits in a little box.....??? I don't want an explosion in a cog factory or to end up with some 'spare bits' left over!

Realistically how easy is is to overhaul the gearbox? I have pullers etc and the usual tools necessary for keeping these cars on the road. Can I just follow the trusty Haynes manual or are there any other publications?
Alan Drain

ThankS Mark,

Thats what everyone else says....So your in good company, guess Ill have bite the bullet and drop it off at the shop.

Hey K.

I dont do trannys or rearend pumpkins, (did I really say that?),,,Then agian Im no expert...but if you dont have good brain knowledge of whats inside that box, I understand it can be a dark and unforgiving place to play....even though there is always lots of candy and cake just outside the coverplate to tempt me inside, I learned along time ago not to talk to strangers....Id say play in the trash pile 1st for awhile before you take on something so important to your driving pleasure as your main tranny.


prop
Prop

Alan if you don't fancy doing it yourself I know a really good box builder just outside Wolverhampton, drop me an email if you'd like his details.
David Smith

Kevin, Alan & David.

I too rebuild Spridget gearboxes, but I guess I'm too far North to be able to help you.

David's contact in Wolverhampton may be closer.

Mark.
Mark Boldry

One quick tuppence to this:

There CAN be one fix which occasionally works for the second gear jumping. When my gearbox failed (stuck in first, worn in all other gears), it was doing the same thing without fail everytime.

I got a rebuilt box from Klassics, who make LOVELY boxes, and it ran beautifully... however I used the same remote and the car has still from time to time suffered the same fate in second, although very rarely. It it worth playing with the plate which holds the stick in place in the remote as the cause CAN be that your stick isn't 'throwing' far enough to engage second fully.

This worked for me. If not, it really is engine out for you...
Rich Amos (1330cc Blaze Red '72)

Whilst this thread is still live, and hopefully Mark is still around my 1275 box seems fine until it gets warm then everything tightens up. Really have to apply much more pressure to get it to shift. Any ideas anyone? Anyone else had this problem? It's been suggested that adding an additive would work, any recomendations?
Thanks Chris
Chris Sargeant

Chris.

I have come across this problem in the past and I would start be suggesting you change the oil in the box. I no longer use the recommended 20w/50, instead I use a semi synthetic 75/90 or 75/80 grade. I feel these grades of oil work well for me and give a good smooth change hot or cold. Mind you, this is on gearboxes I have rebuilt.....
Change the oil and let us know how it is.

Mark.
Mark Boldry

Hi Mark, thanks for the advice, I'll give it a try. Sorry for the delay in getting back I've been working away the last few days.
Chris
Chris Sargeant

This thread was discussed between 01/06/2008 and 05/06/2008

MG Midget and Sprite Technical index

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