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MG Midget and Sprite Technical - Checking an unknown gearbox

As the thread title says.

The box turns, is on its original bell housing, has been out of the car for at least 10 years and is quite rusty on the outside.

Its from a P reg 1500, wondering that it will fit with my early 78 engine. (I am assuming it will.)

Any way I can easily check it its OK to use?
Any pointers I can look for as to its usability?
No oil leaks, looks like it has never leaked.

Cheers,
Dave
Dave Squire 1500

Hi Dave, me again! ha ha!

Yes your box should be interchangeable. Note however that the box and bell housing must be matched. As previously mentioned there were two types of bell housing, one with a scroll seal, one with a lip seal. The gearbox input shaft for the scroll/lip type seal bell housings are slightly different. You can swap them between gear boxes but the input shaft and bell housing must be of the same type.

In terms of wear in the box there isn't that much you will be able to see on a quick inspection. From what I have read/seen/replaced the wear items are:

No.1. The layshaft and associated needle rollers - you can't inspect the condition of this without dismantling, but probably knackered!

No 2. The big input and output shaft bearings (input is first to go I think, followed by the output). You might be able to test the input just by putting the box in neutral and spinning the input shaft and feeling whether it spins freely or whether it feels rough/noisy.

You could drain the oil and see what condition that is in, although if it has been changed "recently" that won't tell you much.

If you take the top cover off you will probably spot one of the gears has a load of chipped teeth. This is the reverse gear and they are all a bit mashed so don't panic too much about that!

A question to ask yourself as well... if this box is good, why is/was it not in someone's car? If the car was broken for spares due to rust or whatever what are the chances it had an excellent gearbox but a badgered rusty body?! Pretty slim I think.

Cheers for now!
Malcolm
M Le Chevalier

I've checked the odd gearbox in the past by chucking the input shaft in a drill and then running it. That allowed me to check for noise and the shift can be checked to see if the sychros seem OK.
David Billington

Good advice Malcolm.

The car its out of was taken apart and boxed up by a guy who was an engineer for a sub contract company that made engineered control systems for ships. He had rebuilt several classics previously. He had refurbed all the doors etc. and boxed up and labelled the bits. I think there is a good chance he chose a mechanically sound car that he was welding up. (the stuff he did is vey good, just not much done on the main shell), so for instance I have two superb doors ready for the guts to go back in finished in primer, some spare structural panels for all the right parts that are rotten, brand new main and heater radiators, and no quarter lites (presumably too bad). Anyway they shut the company and he had to find something to do. Became a driving instructor, makes more money, but has a lot less time. The parts and body stood around for several years; I had a van big enough to fit it all in at the time, it was an easy drive just off the end of the M11 in London and he offered it free for collection. I took a day off and a lad for a day and so that's history and the 'final frontier' arrived. (and the 40 years my SWMBO didn't know it was another car in the yard for nearly two years ;-). I didn't get told off cos it looked a mess but it is an asset. (her words not mine) :-)

Anyway, the more I think, the more I know I need to try this box anyway. Firstly I need to know if it works OK and hopefully it should then give me time to try sorting my existing if I need to. The 'new' box has its bell housing attached so I will probably go with it if it passes your tests. I will get a top cover gasket, see where the oil is up to, what it looks like, and as you say the bearings and teeth before committing to use.

I think that is probably the best overall plan for now. As regards the rest I will get a rear engine seal, some replacement fly wheel and clutch cover bolts and a clutch. (maybe even a clutch kit and guide tool):-). Then the bits Alan is suggesting and I should have an interesting weekend in a couple of weeks.

Thanks again, Dave
Dave Squire 1500

I mentioned on the other post and idea

Hook up the input shaft (front) to a drill and give the each speed a good spin and listen for any bad noises

Pull the cover and have a looksy

Prop
Prop and the Blackhole Midget

Visually inspect the reverse gear and the scycrho hub that engages with it... these wear at the edge to the tooth badly and will mean when you pull off in 1st (1st shares the same synchro hub as reverse) it will make a hell of a noise.

Rust on outside is not an issue. I would fill box with thin oil... parafrin or something like that... and run it on an electric drill (i mounted mine on a lathe and ran it for ten mins) ... then emptied all the black oil... nice way to clean it out.

C
Christian Carter

I dont know about cleaning it out with parafin (kerosene) or thin oil

If its bad inside then it could be the crude is acting as gap filler in any bearings....loose your bearing, you loose your tranny, loose your tranny then you loose your mind, loose your mind you will buy a triumph....dont be the guy that buys a triumph

Prop
Prop and the Blackhole Midget

This thread was discussed on 13/02/2014

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