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Author Topic: Reverse Gear Problems and Overdrive Transmission  (Read 15928 times)

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Reverse Gear Problems and Overdrive Transmission
« on: June 25, 2012, 05:11:48 PM »
I am having difficulty placing my '74 B into reverse. What should I be looking at for repairs and costs?
Ron Mansi
« Last Edit: December 31, 1969, 07:00:00 PM by amgba »


  • chfwrench
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  • MG information: '73 red B roadster
Re: Reverse Gear Problems and Overdrive Transmission
« Reply #1 on: June 25, 2012, 05:12:42 PM »
Used transmissions, unless verifiable as recently rebuilt, are a short-term solution as they are at best just a few years newer than yours and, regardless of how inexpensive they are to buy, still mean removal of the engine to install. Even if you do this yourself, it is neither so easy nor cheap to want to chance having to do it more than once.
The Victoria British Catalog ( charges about $1,000 plus shipping for an outright buy (no sending the old one back for credit) fully rebuilt 4-speed synchro box as would be in your car and that would be a bolt-in replacement. Moss Motors ( is about the same.

If the car is equipped with overdrive, while the actual transmission is the same price (about $1,000 plus shipping), the cost does not include the OD unit, which would have to be transferred from your old gearbox, and then would not have been rebuilt, or purchased separately.

An overdrive unit alone is another $1,000 rebuilt. They have to be purchased separately as neither catalog is offereing complete assemblies.
If you can find a shop familiar with these gearboxes, chances are a repair or even the rebuild might be cheaper. Considering the age of your car and that it has likely not been rebuilt up to this point (or at least not recently), a full rebuild should be expected replacing all bearings and wearing parts.

Moss is now offering a replacement modern 5-speed gearbox at a cost of about $3,700 for the kit (which includes a new tranmission rear support and driveshaft parts). No electric OD is necessary and, if you plan to keep your car forever, it makes gearbox/clutch repairs much easier as they can be removed/replaced with the engine still in the car from beneath.

I strongly suggest either the overdrive or 5-speed conversion. Makes for more confortable cruising, better mileage and reduced strain on the driveline at highway speeds. As yours is a '74, adding the OD is easy. The driveshaft remains the same and the switch is already in place on your windshield wiper stalk. You need the correct gearbox, OD unit, engagement switch for the trans (I donít believe it comes with the rebuilt units) and the switch harness comes as a complete kit. Then it is just the job of installation, which even if you had to pay someone to do, is the same as replacing the original box.

Last year, my '73 B started making transmission noises, which turned out to be the input shaft bearing. A repair would have been relatively cheap, but the box has in excess of 120,000 (known) miles and near 40 years of service to it. I also have a spare 4-speed thatís been lying around for years that was supposedly good when I got it, but the thought of going through it all to find out did not thrill me. In the end, I was offered a year-correct overdrive box with a documented recent rebuild. Works great and I love the difference it makes. See the photos of the the conversion.

I hope that helps you. Write or call if I can help in any way.

Safety Fast!
Art Isaacs
Art Isaacs
AMGBA Tech Staff


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