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MGB Gearbox Rebuild


Freshman Member
Greetings. I am new to this forum and look forward to you guys helping me restore a 69B. Right now engine and gearbox are out with engine off to get rebuilt. I am considering breaking down the 4 synchro gearbox, with LH overdrive, doing inspection and repair/replace parts as needed. Have never done this but do have many years experience in machinery repair and mechanical experience . Wondering just how difficult it would be. Any tips/advice would be appreciated. PS, I purchased car that was sitting for 15+ years, in pieces, so am not sure of just what kind of shape internally the gearbox/overdrive are. Cheers, Marty

Mickey Richaud

Staff member
Country flag
Welcome, Marty!

You'll find that these engines and transmissions are pretty robust units, but age and non-use will take their toll.

The B gearboxes are especially stout, and the overdrive units are as well. If it's been treated well, it may only need a refresh - seals, pump for the o'drive, etc., and maybe a bearing or two.

Over on YouTube, you'll find some very helpful information submitted by John Twist of University Motors. He has several episodes on transmissions and overdrives. Here's one to get you started:

Let us know how you get on with it!



Great Pumpkin
Country flag
Welcome aboard, Marty!

Mickey's link will get you started, the gearboxes are really straightforward units. You shouldn't have any real trouble. I'd further Bre'r Micks suggestion and recommend replacing ALL the bearings along with the seals. Layshaft and bearings are the "weakest" part of the box.
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