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MG MGB Technical - Late gearbox, internal parts question.

Just when I finished changing the front and rear seals on a late gearbox and was congratulating myself, I find it.... one part left over.

It's a ball bearing, about 1/4" diameter. At first I didn't think it came from the transmission since I didn't see it until I was cleaning up my workspace. But then I found part #329-550 listed on Moss' current catalog page #38 which could be it. The only thing I can think of is it fell out of the transmission when I had the front cover off. This is a spare transmission which I've never run so I don't know anything about it.

My questions are if it is a "synchro ball" can it be replaced without removing the innards or is a complete disassembly the only way to replace it? Are there other loose bearings or likely suspects that may be the culprit?

I'm at my "technical proficiency" with changing the seals, the idea of opening the case and jockeying the gearing is daunting. As an alternative I can get another used transmission but then again it's condition is unknown.

Your experience and insight are as always appreciated. Thanks for your time.

Brian Denis
Brian Denis

I just took off the front cover and see no way that a ball bearing could migrate there. I haven't pulled the rear seal yet but looking at the ball bearing it seems too small to be part of the rear mainshaft bearing, but I don't know.

During the work I did have the side cover off for a quick inspection but again I didn't notice the ball bearing until later. Is there a way to visually inpect to see if a "synchro ball" is missing?

Brian Denis
Brian Denis

If it is P/N 329-550, you need to strip the box to replace it.
Art Pearse

Art, thanks for the response, unfortunately I was expecting that answer.

Looking at the gearing and diagrams I don't see any way that the ball could come loose while the gearing is installed.

Anyone with experience with this part found floating around in the gearbox?

Brian Denis
Brian Denis

Brian,
I've rebuilt an A series (mini) box and I'd be very surprised if it's come out. More likely it "went missing" during build/ rebuild! I know from experience how the syncro balls can fly in all directions when trying to get the hub in place! Still looking for two that shot over my shoulder in the garage!!!
That reminds me, if you do strip it (and to be fair they arn't that difficult just a little daunting the first time) wear safety glasses!!!!

MGmike
M McAndrew

Brian,
One other thought. There is a ball used in the reverse gear gate. Did you have or are any of the selector items loose? Check the reverse gate and indent plunger.

MGmike
M McAndrew

MGmike, thanks for the suggestion. I only had the front and side covers off, and changed the front and rear seals. All the selectors appear tight.

I did check the reverse gate & indent plunger as you suggested.... assuming they are accessed from the bolt on the case next to the reverse light switch. There was no ball, but there was a rounded end plunger (Moss part #462-480?) at the bottom of the hole. The diagram in the Moss catalog is confusing, I see both the plunger and a ball (part #329-520) represented.

Thanks again for your time and suggestion, all are welcome.

Brian Denis
Brian Denis

Brian,
I've rechecked the Moss Europe site and a late 'box has the rounded plunger and not the ball! That leaves the syncro and a possible strip down!!!!

MGmike
M McAndrew

Brian,
Just spotted another likely candidate! I'm assuming you have an OD box? The overdrive pump cam on the main shaft uses a ball to locate it. It could have come out when the front cover was taken off if all the internals slipped forward!
Check it out by removing the OD side plate and filter and check the pump moves when you rotate the mainshaft. You'll need new gaskets to reassemble....

MGmike
M McAndrew

MGmike, I really appreciate the time you've put into my dilemma! Unfortunately no, not an OD box! Over here an OD box is +/- $1k but a regular box is <$100.

I had one opportunity at an OD box a few years back. I had a parts car with and OD box that I got running and sold for less than the value of the OD. All I had to do was swap the boxes with my running MGB and I would have had an OD. But at the time I had installed and removed engines and transmissions multiple times within a few months and I was cooked. I regret being lazy now.

Again, thanks for your time and interest. I think I'm headed to acquiring another 4 gear box. I can't risk installing this box only to find out it's not right because of a missing synchro ball. Some day when I'm brave I might strip the box.

Brian Denis
Brian Denis

Brian,
Time is no problem. I'm sure the reaserch will turn out useful if (when) I need to do a slimilar task!
Sounds like I should buy up a load of OD boxes and import them to the USA!!!!
Best of luck with the new box...

MGmike
M McAndrew

Brian,

If you are fairly sure that this 1/4 inch ball bearing came out of your box during your re-sealing of the GB, you probably should not consider installing it in ANY MGB without a complete disassembly and, while you’re at it, a complete rebuild. There is NOTHING in the GB that should “float” out of the GB like that and end up at the front or rear seal area without major problems internally. If someone was playing a practical joke on you, HA HA!!!! But still, there is NOTHING that can fall out of either a Non OD box or an OD box while replacing just the seals. Out of curiosity, does this box have a dip stick or a side level oil fill? The boxes with the dip stick, and possibly some of the later boxes with the side oil fill, used BB for the shift rod indents. I believe MGmike motioned this already but my understanding of your response is that you were looking in the wrong spot. There are 3 hex caps close to one another on top of the box near the bell housing part of your GB. Again, they are very close together. If you unscrew these 3 caps you should find a spring followed by a plunger or a BB. These are in the 1/4 inch vicinity too but again, no way for them to fall into the GB without other major disassembly or internal problems.

As you already mentioned/indicated these boxes are available for <$100.00 and probably not worth going through it. You can use it for spare parts or just the exercise in how to disassemble a box, for the drill of it. This part of the box is the same in an OD so the experience might be worthwhile. As for an OD box, I have one available out of 1969 MGB-GT and will throw in a standard box with it for less than $1K if you are interested. Not sure that it could easily be shipped but both are available just north of Phila, PA. For the couple dollars more I will reseal the OD box, replace the lay shaft and shim the front bearing.

Fred
Fred Wright

Fred, thanks for your comments. My assumption is the bearing (if it even came out of the gearbox) was loose in the case, probably got away during a rebuild and fell out when I opened the side cover. You're right, theere is no way a loose bearing could escape while removing the front cover and rear seal.

I did check the three rod indents and I have springs and plungers in place.

I came to the same conclusion that you recommend. If I won't install the gearbox because of the uncertainty then why not use it as a learning experience and have a go at a strip down.

Any suggestions on how to organize things so that everything goes back together is appreciated. I have a Haynes manual which will help. However the process outlined in it is for an early gearbox and I have the later model.

Brian Denis
Brian Denis

This thread was discussed between 25/06/2011 and 29/06/2011

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