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MG MGB Technical - Broken Synchro Ring - Why?

I am in the process of restoring a '69 MGC. In rebulding the trans I found a broken synchro ring which someone had brazed back together (see photo). As the B and C transmissions are very similar I was hoping someone here on the B board might be able to tell me what would cause this. I've successfully rebuilt B and TD transmissions so I know a LITTLE about what I'm doing but not nearly enough in this case. And while I don't think they are related one of the planet gear bearings in the O/D was completely destroyed. Not what I was hoping for, but it keeps it interesting.

One more thing, the part number on one of the sliding hubs faces forward the other to the rear. Does it matter?

I'd appreciate your thoughts so I can figure out what else to check before I reassemble it.

Thanks!
Jim

James Budrow

MGC boxes are marginal at the best of times and it is not unusual to find broken parts in them - indeed many original MGC boxes have had the internals replaced with MGB parts, simply because original MGC gears are so rare and fragile. The MGB ratios are different however and no stronger!
Chris at Octarine Services

Can't address that specific part's uniqueness to the MGC instead of the MGB, but can speculate why. I had an MGC back in the mid 70s. Found it under a tarp in a backyard with 23K on it. It was white, so buffed out beautifully and cleaned up inside and out to look like new. However, after waiting 6 months for brake servo parts that had to be located, ordered and shipped out of Italy at ridiculous prices, I decided to let the car go. The same applied to MGBs as well. I let my 70 MGB go in 1988 after owning it since 1971. The wire wheel hubs were wearing down and the rear end needed to be replaced after about 250K miles. The only used rear end I could find was priced at $750 with no guarantee.

The expiration and/or release of patents to companies like Moss and others in the 90s has made a tremendous revival possible. Thus, a previous owner of your car may have had no other choice. Just a few parts back then cost more than the car was worth if you could find them at all.
Rick Penland

This is a very common complaint with MGB boxes as well
I have rebuilt B boxes many times. It is caused by slamming it through the gears to fast so it is not unusual in a car that is raced. One Customer I had broke either 2nd or 3rd baulk ring every second meeting.
Garth.
Garth Bagnall

It's either that or someone has been changing gear badly without using the clutch.
Iain MacKintosh

Sounds like I should just replace the baulk rings and check the rest out carefully. Whoever had the car beat it up pretty good but the gears themselves are all in good shape. At 60+ I don't beat my cars the way I did when I was younger so I'm reasonably sure it will hold up fine as long as I don't miss something in the rebuild.

Thanks for your comments - always appreciated!

Cheers,
Jim
James Budrow

The ratio spread on the MGB 4 synchro box works quite well. Driving through the non o/d 3.07:1 MGC back axle it should suit the car OK.Of course the greater torque of the bigger engine would pull a sporty set of closer ratios Top is 1:1 anyway so you will get the 25MPH/1000 rpm long legged cruising the C is famous for.
Stan Best

This thread was discussed between 07/12/2009 and 08/12/2009

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