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MG MGB Technical - Cluster Gear - 3 Syncro - Who makes them in UK?


Anyone know who makes a 3 Syncro cluster gear in UK ?

They seem to be £160 from Moss but the 1st gear is also almost the same price at £155, so an expensive pair.

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=139

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=135

Obviously I have a broken set and require replacements.

Anyone know a good source in UK ?

Is the 3 hole layshaft cluster the same part number as the 4 hole (which I have) ?

Thanks
Mark

Mark Hester

I have some 3-sync gears somewhere.

I'll have a look tomorrow.
Dave O'Neill2

Mark-
The three hole layshaft is BMC Part # 1H 3305 and has a diameter of .643". The MGB version of the three-synchro transmission used the same laygear for this layshaft for all years of production (1962-1967).

The four hole layshaft is BMC Part # 88G 400 and has a diameter of .668".

Obviously, the laygears (Three hole laygear BMC Part # 22H 54, four hole laygear BMC Part # 22H 1301) are not interchangeable.

It is possible to modify the earlier three-synchro transmissions (found with the 18GB 74529 and earlier engines) in order to install the stronger, larger-diameter “four-hole” layshaft (second motion shaft) assembly by boring out and line reaming the layshaft (second motion shaft) mounting holes to .6693” +/- .0005”. (17.0002mm +/- .0127mm). The best, and easiest, way to do this is to use an “end bell reamer” that is used for reaming the holes in the end bells of electric motors. This is a piloted, adjustable reamer that is adjustable (over a small range) to give the proper diameter and clearance. To keep things in line, it pilots in one hole while it cuts the other. They are commonly found at shops that rebuild electric motors, and the technicians there should do the job for a nominal fee. You will, of course, need to use the corresponding later laygear in order to fit onto the larger-diameter layshaft (second motion shaft), along with its front and rear thrust washers, caged needle-roller bearings, and its larger-diameter distance piece.
Stephen Strange

Interesting new kit listed by Moss USA regarding improvement of the MGA/MGB 22H0054 3 hole design. The improvement seems to be stronger & more durable than the 4 hole design. If I were to rebuild another 3 synchro gearbox I would most likely use it. The price seems decent since the kit contains the laygear, layshaft & bearings + a dummy alignment tool. You can always find low cost used MGB gearbox cases that use the 3 hole layshaft. In any event; installation of a replacement laygear requires a complete gearbox dis-assembly anyway. I have always used the 4 hole design on my rebuilds.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=110643
Rich Boris

Look closely at the image of the straight-cut gear teeth that Moss chose to use for their advertisment. Is that bottom tooth cracked?
Stephen Strange

If rebuilding with a new 3 hole layshaft, get the hardness checked as there are some dodgy ones around. they should be 61 rockwell, but some are as as soft as the low 50's and don't last at all. The best I have found was only 59, will last reasonably well but still nowhere near the roiginal. I have resorted to having them made to the correct hardness even if it does cost more.
If it's not hard enough, take it back and get another.
Paul Walbran

I've been watching this series of comments with great interest as my Mk I O/D gearbox is approaching the point where a rebuild will be needed in the next 10,000 miles or so.
The quality of the replacement gearbox components has concerned me; in particular I believe the steel synchro rings currently sold are poor compared to the originals. Paul Walbran's comments re shaft hardness are both interesting and not surprising. Having had some significant disappointments with the quality of parts from Moss (and other suppliers), I might hold off with the Moss upgraded shaft and bearings till I hear of more feedback and comments.
In the meantime, to play it safe, I've bought this:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=130827724549#ht_788wt_1015
Hopefully, being an original part, the shaft hardness should be up to spec.
T Aczel

This thread was discussed between 02/01/2013 and 05/01/2013

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