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MG Midget and Sprite Technical - 1500 gearbox REBUILD KIT

This message is mainly targeted at John Barber and anyone else who has recently rebuilt their 1500 gearbox.

I've got my gearbox out on the bench and I'm in the middle of stripping it down. So far I've managed without any of the "service tools" - most of which look from the diagrams to be crude bearing pullers. I've made my own pullers which work much less aggressively.


In terms of rebuilding. What parts did you replace? Presumably bearings and seals and gaskets. Did you buy a kit? - are the bearings in the kit SKF or RHP... or are they made from chinese cheese?

I need to replace the reverse idler and 1st gear.

I am contemplating replacing the syncrho mesh... but is this necessary unless worn?

Any good place to get this from?

Cheers
Christian


C L Carter

Hi,

I'd deffo change the baulk rings, they are relatively cheap and it would be daft not to.


Examine the teeth on the synchro hubs carefully, if you can't see obvious damage, re-use them, as they're expensive! But don't slide them too far apart or you'll have springs and ball bearings flying everywhere. Not easy to put back together either!


Good luck.

Regards Steve
SR Smith 1

I did mine at the same time as John. I got the kit from rimmer bros. Replaced everything that the kit gave me! Off the top of my head the important bits are...

Synchro rings
Input/mainshaft bearings
Layshaft needle rollers
Layshaft
Thrust washers
Gaskets and seals

Kit is here...

http://www.rimmerbros.co.uk/Item--i-GRID005697

Quite expensive, I was fortunate to get mine in a sale where things were (i think) 20% off.

Only tools really needed are circlip pliers, levers, hammer. I came to the conclusion it's more difficult than an engine rebuild.

Cheers,
Malcolm
Malcolm Le Chevalier

Whilst you're at it, why not consider an overdrive conversion from a triumph spit or dolly, makes the 1500 a far more useable vehicle.
SR Smith 1

No good reason to replace synchro rings if they are not visibly worn. You can compare the depth of engagement of the cones by comparing them on the gears - if one goes on a lot further than the others, it (or the gear) is worn. The top gear one is usually not worn at all, so it makes a good comparison gauge. Reason to not replace is that I've heard numerous reports that repro rings are not nearly as good as OEM ones, no personal experience, but it fits everything else we know.

The single most critical item is the stupid fat circlip that holds all the pieces on the third motion shaft; it is all too easy to overstretch this, as it is a beech to get on - and when one breaks in service it usually takes out the third motion shaft and numerous other bits. I would never reuse one of these things, as the worst damage comes on removal; the first time it is installed is one stretch, but if reused it is at minimum three stretches, which is four too many!

FRM
FR Millmore

Thanks guys thats good information.

I'm thinking at the moment of aquiring a few old gearboxs and making the best out of all of them. I can't afford to spend £150 on the 2 gears I need as well as the £150 of bearings and bits.

Can anyone give me and idea of how much it costs to put in a 5 speed? and where to look?


C L Carter

Christian, I didn't buy a kit - I looked at each component for wear and then went from there - I ended up with gaskets & idler gear which was badly chipped -but found most other parts useable. My synchros weren't too bad so didn't put in new either. For 75k the thing looked pretty good except the idler - I assume this had got abused by prior owners going from first to reverse before it had fully halted...

I actually found all the clearances were okay on reassembly. The only reason I stripped it in the first place was to cure a rattle in first gear ...
Hope that helps...
John Barber

Thanks John, thats the same reason I swapped my gearbox - but the replacement is giving me issues so I've decided to rebuild the one I took out.

Actually - I'm at the stage where I'm trying to remove the shafts and gears from the box... and when I try to pull the rear shaft out - the 1st gear fouls on the inside of the box and I can't get the bearing out any further - did this happen to anyone else?

C
C L Carter

Christian, do you mean the main shaft assembly? I followed the Haynes manual instructions and found it mostly worked according to instructions except in one or two details which they missed..
John Barber

Yes - The main shaft assembley... how does it come out of the box? Rearwards or forwards?

I'm using the workshop manual... I don't have the haynes.

Did you use all the service tools John?

C
C L Carter

>>I followed the Haynes manual instructions and found it mostly worked according to instructions except in one or two details which they missed..<<
what Haynes, no never :)
Nigel Atkins

Nigel, you are always knocking Haynes. But in truth, the publication by John Haynes of simple and straightforward model by model guides enabled a whole generation to tackle basic and not so basic maintenance work on their cars. For many years proper workshop manuals were either not available to the public, or were extremely expensive. OK, Haynes manuals do have occasional errors and omissions, but very few publications don't have. They also in the introduction always used to invite readers to notify them of any errors so that later editions could be corrected.
Guy W

Guy,
part of the reason for this is because most new classic owners know only of this publication and rely on it not knowing better

same way the first most think of with the car is to tune the engine or carbs

having a Haynes and tuning the engine or carbs have there place but it's not first place

I've got two Haynes for my 1973 car, 1974 and 1980 prints, the 1974 doesn't cover my 1973 car and the 1980 carries over errors and ommissions from the earlier prints

personally as a non-mechanic I find the Haynes either pitched too high, probably I'm just too thick to get it, or far too low and missing a lot of what I could understand and want to know

had I been able to have a Spridget in 1974 or 1980 I would have got my quill and partchment out
Nigel Atkins

Christian, I didn't have any special tools to strip and rebuild - you can imporvise anything you need.

Bear in mind the main shaft is in two parts the input shaft part which is splined intothe clutch plate at the flywheel end and then the output shaft which is splined into the propshaft flange at the other end. The way I got mine free was by getting the input shaft end out first - once the bearing is pulled out from the casing the whole input shaft can come through as I recall.

Then the rest of the output shaft is lifted out from inside the beargox casing - get the bearing knocked /pulled loose and you can tilt the shaft and lift it out of the casing.

To get to this stage the idle shaft/locking bolt and shaft must come out first..

I have some pictures of reassembly - but not strip down unfortunately...

Hope that helps...
John Barber

Yes John, that does make sense. The input shaft does need to come out first... but I can't come up with a way of pulling the bearing out? How did you do that?

C L Carter

Two methods used together sparingly..

Firstly once all the extension and other stuff is out of the way - you cn tap the output shaft end - with the flange nut on to protect the shaft threads .. Just need to get it to move a lttle and then :

Secondly lever underneath the snap ring that is mounted on the bearing itself- I found it came out reasonably easily once you could get underneath with a srewdriver /lever of some sort ..

Good luck
John Barber

Yep, +1 to that. If I remember rightly...

Get the layshaft out the way and leave the laygear cluster in the bottom of the box, and the same with reverse gear.

Then I boshed the end of the output shaft with a heavy rubber mallet (with the nut still on the shaft) until the input shaft came out. (With rear housing and all the gubbins removed. Locking the 'box whilst undoing the nut can be a fiddle, I just wedged a spanner/screwdriver in somewhere 'cos I'm a pikey! CL I know you like to do things properly!)

The bosh the output shaft the other way to get the rear bearing loose. Jiggle and pry the bearing free. Lift the whole lot out the top of the box (actually took me ages to figure it came out the top, not the back! ha ha!).

Cheers,
Malcolm
Malcolm Le Chevalier

Ah okay then.

I did try applying some gentle force that way with the nut on - but it didn't shift - I might use the bearing press to do this - presuamably you need to remove at least one circlip before you do this?

I did try pulling the rear bearing out first by winding it out using the thread on the shaft - but this meant the gear on the inside fouled on the inside of the box - thats when I decided the input shaft needs to come out first. But then I got stuck.

Right - Onwards. Will have ago at your method tonight.

Thanks chaps
C L Carter

So all out and apart - can't seem to easily get the last few gears off the output shaft, will deal with that later.

So the reverse idler was knackered (see photo)
And the outer sychro which is mates with is gone too... the layshaft gear isn't too great but I think i can live with it.

I will be looking to pick up spare box on ebay to see if I can pinch some other parts.
C L Carter

This thread was discussed between 19/08/2012 and 22/08/2012

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