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MG Midget and Sprite Technical - Gearbox part needed: #?

I had a thread going a couple of weeks ago about my gearbox jumping out of top gear. The gearbox concerned is one of the smooth-case gearboxes with the close ratio gears and cone synchromesh that were fitted to the Sprite 2 and midget 1 with the 9CG 948cc engine.

The part needed to fix the problem is the 3rd-4th gear synchro block together with the coupling sleeve that runs on it and is moved by the selector fork. This sits on the mainshaft with 9 splines, and the coupling sleeve internal splines are very worn. I thought I had obtained a suitable replacement with a good s/h 2A 3226, as fitted to Minors and the like, but this turns out to have 10 splines to fit to the mainshaft.

Please can anybody help me with my search by telling me the part number of this bit? It doesn't seem to get a mention in any of the parts books that I have available. Daft thing is I probably had the part inside a much cut about smooth case ex-racer gearbox I unloaded on eBay to a bloke near Reading a year or more ago, just because I needed the space. If necessary, I'd buy another complete box, just for that part.

G
Gus Gander

I reckon the 3rd-4th sync assembly is 28G134 and the sleeve is 2A3145. This from an original 2nd edition of the Midget Mk 1 parts manual. (the disconcerting bit is that the item #s on the picture don't match the item #s on the text list).
HTH.
David Smith

Thanks David. This certainly does help, as I hadn't even got a start on this otherwise. At present I've taken the sliding coupling sleeve off the '10-spline' synchro I've bought, to try to fit it to my original '9-spline' block. They are obviously intended to be the same, but the new sleeve is a very tight fit on the old block, so I'm busy trying to emery them into compliance. This could take a very long time, by the feel of it, so a replacement would be much better. I get the impression that the part is the same for both the Sprite 1 AND Sprite 2 boxes, so I suppose I'm in with a chance of finding any smooth-case gearbox.

gusgander'AT'blueyonder.co.uk
G
Gus

I saw a smoothcase on ebay last night, fairly recent listing ISTR....
David Smith

When I last looked there were three on e-bay (I confess, one is mine).
Chris H (1970 Midget 1275)

Gus,

I am pretty sure that the early Frogeye smoothcase box is the same as the 948 Minor/A35/A40, and is the 9CC box? Same ratios and bronze bushed 2nd and 3rd gears.

The later Frogeye smoothcase is the 9CG box with the close ratios that was carried over to the Sprite Mk2 and Midget Mk 1. This also had the needle roller bearings for 2nd and 3rd gears, which I think results in the unique parts that you need? Both the close ratios and needle rollers were unique to Spridgets and were carried on to the 1098 and 1275 baulk ring boxes.

The Minor/A35/A49 etc. never had the needle rollers or close ratios, but did get the baulk ring box with the 1098 engine.

Richard
Richard Wale

Here is a list of Spridget transmission parts from a very old list that I have had for about 30 years. It seems to be pretty complete and correct:
http://www.britishcarforum.com/bcforum/ubbthreads.php/ubb/showflat/Number/407639/Searchpage/1/Main/41511/Words/transmission/Search/true/Re_Transmission_partslist#Post407639

Bill
billm

Gus, IF you are still looking I have located amongst my gearbox parts a NOS (still in original BMC Box) 28G134 the third / fourth synchro block and sleeve.
Call me on 07889 799033 or 01904 400998 to discuss...

Mark.
Mark T. Boldry

Thanks everybody for your help, offers and suggestions but, being anxious to get on and finish this car, I remembered Hardy Engineering at Leatherhead, who found me the bearings and layshaft for its original rebuild, so I asked them and they supplied a good s/h one, which I have now fitted. They are very prompt and much to be recommended. Also to be thanked are the Bywaters, who deal very efficiently in gearbox parts for Minors under the pseudonym of 'Mirabelle'. They've been very helpful. Thanks too to Billm in Seattle, whose comparison chart hasn't scanned very well, but serves to confirm or deny a suspected part number.

Let's hope the whole thing works properly now!

G
Gus Gander

That didn't scan so well but if you open the "file" it is an Excel spreadsheet of all of the numbers and is much easier to read.
Bill

Good luck with your trans work!
Bill Masquelier

This thread was discussed between 15/10/2008 and 22/10/2008

MG Midget and Sprite Technical index

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