American MGB Association

North America's oldest, largest and best club for all year MGBs, MGB-GTs and Midgets!!  Established in 1975.


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for all year MGBs, MGB-GTs and Midgets
Established in 1975

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this is an excerpt from the articles appearing in the OCTAGON

also see upkeep and performance hints on our message board at
and on our Facebook group at

Please note: Questions and Answers and Upkeep and Performance Hints are provided for information and advice purposes. No liability either expressed or implied is assumed by reliance on the information presented either by the writers or the AMGBA.

Some or all of the below is from our message board at, Facebook group at This is just a part of what appears there and in the member magazine.

Also be sure to see our message board on our website and Facebook group for immediate help from fellow members.


Q:     I picked up a used overdrive unit to install in my 1977 MGB. The gears look excellent in the gearbox and the gearbox turns smooth through the gear patterns when I turn the input shaft. I will change the front and rear main seals plus O/D filter. There is a cover plate missing from the O/D unit and what I think is from MOSS parts catalog the coil assembly. I’m not sure if its stuck up in there from the pictures or all missing? If stuck how would you remove it? See pictures

Please fill me in on what you know. I can make the cover plate out of aluminum from a new gasket used as a pattern. Throw in any other suggestions.

Oh is this a drop in replacement for my old 4 spd?


Fred Mauro
Bethlehem, Pennsylvania

MGB overdrive unit MGB overdrive unit

A:     You’ll want to purchase a new solenoid assembly. It’s available from Moss #80 on page 41 – 466-375. Remove the remainder of the solenoid assembly with a pair of needle nose or duck bill pliers. The piece you’re trying to remove looks like a top hat and you’re looking at the bottom of it.

I’d clean out the overdrive and replace the O rings right now while it’s out.

Oh – if it’s a top fill gearbox, then it’s probably set up for 1280 turns per mile on the speedo cable; if it’s a side fill gearbox, then it’s probably set up for 1000 turns per mile. You want the later, 1000 tpm for your car, or the speedo will read 25% fast.

Except for the wiring, it’s a straight drop in. Make CERTAIN you check the 4th gear switch about 20 times. After installation it’s the least accessible electrical component in the vehicle. It’s at the right front of the top of the remote control assembly.

Hope this helps.

John H Twist
University Motors Online
Cell: 616 307 6737

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