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MG MGB Technical - 3 vs 4 synchro gearbox interchangability

Hi All,

After having solved my engine shaking problem and now can drive the car, I have found that the gearbox is stuffed.

My question is can a 4 synchro box be bolted directly in place of a 3 synchro box, both Non O/D.

TIA

Herb
Herb Adler

Herb -
Along with a lot of other essential info:
http://www.mgbmga.com/tech/index.html
Specifically:
http://www.mgbmga.com/tech/mgb1.htm

The car I just got has one in, done by a resourceful amateur throw it together type - I haven't yet dared to examine it! But, I drove it home 500 miles. A lot of cold air where the shift tower pokes through the tunnel in the wrong place! He used the 18GB starter, flywheel, and engine plate. "Some of the bolts didn't line up, but there's enough".

FRM
Fletcher R Millmore

Hello Herb,

I am currently realizing this to mate a T9 box.
I retained the original 18GA backplate with a rear journal seal modification, a 18GB flywheel ( narrower )
Original inertia starter can fit in. I can't tell if 4 sync. box easily gets in the narrower tunnel, may be FRM answers this point?
Guy RENOU

I did this to my '67 that had a 3 synchro trans on its way out. I used several components from a '68 or later car to make the installation simpler. The backing plate, starter, and flywheel, from the later car, made it a bolt in job. The only modifications were relocating the shift lever 2 inches aft and slightly hammering out some extra space for the od unit. The drive shaft will have to be replaced, as well, as they are not the same length. I did this 20 years ago and the car still runs great. A massive improvement over the old weak trans. RAY
rjm RAY

Thanks Guys

I was offered a 4 Synchro box, but with the amount of modification necessary to the it and my lack of other necessary parts, I think I will just buy a Nissan 5 speed and fit it. Sounds like the same amount of work and probably much cheaper.

Thanks again.

Herb
Herb Adler

"I think I will just buy a Nissan 5 speed and fit it"
Not really an MG solution but definitively a nicer tranny: lighter, more modern design, quicker shifts and perhaps even better ratios.
Guy RENOU

This thread was discussed between 06/03/2010 and 07/03/2010

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