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MGB MGB GEAR BOX

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WJM

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Hi all Im new to this so stay with me. I have a 1972 MGB and want to put a over drive box in. Is this a problem or is it easy to change from standard 4 speed to OD box. /ubbthreads/images/graemlins/savewave.gif
 
Hi, WJM -

Welcome to the Forum!

My understanding is that the changeover is quite simple, as boxes were interchangeable. I'm assuming you will have a complete transmission with overdrive available. The length of the two units are the same, so you don't have to change the driveshaft. The only thing you'll have to ensure is that you have the wiring and necessary electricals (be especially sure to put in a new overdrive isolation switch).

Keep us posted on your progress.

Mickey
 
It's a pretty straight forward swap. As Mikey says, you will have to add another wire from the yellow o/d feed wire on the passenger side of the engine bay, or get the factory style harness which includes the wires for the reverse lights, as well. Engine has to come out, a longer 72" o/d speedo cable has to be used as well. Besure to go back with a new clutch to save having to pull the engine again in the near future. Make sure the tranny you get matches the speedo TPM that's in your car. And check BOTH switches, reverse and o/d lock-out, on the tranny before you install the tranny in the car.
 
New speedo, wiring, and a new driveshaft I'm pretty sure. Its pretty costly for an extra gear or two but I've heard it was worth it. There is a 5 speed kit that I woudl go with if I was looking into it from Rivergate Racing.
 
Hi. Thank you all for such quick replys. ADAM 90009 says you can get a 5 speed box is this for MGB or can I get a box from another model of car. I am in Australia I dont know where the rest of you are from. Maybe some of you are in OZ as well. Regards WJM (Sorry all just noticed your locations is listed down the side of your names. SILLY ME) /ubbthreads/images/graemlins/nonono.gif
 
G'day........don't know if you got the Ford Sierra in Oz, but I have heard that the five-speed unit from this car is a good match with the MGB, and that you don't even need to shorten the prop shaft.......you might want to do a little research to verify this, but I think that I have the basics about right......the old memory ain't what it was! Good luck.
 
Hi Steve and G'Day to you. Thank you for reply. No we dont have that model here but will check it out incase it comes under a different name. Regards John
 
Adam 90009 Thanks that makes things much easer. We have the old datsun out here . Regards John
 
If you use the MGB overdrive unit get one that is a top fill box, has the dip stick on the top just like yours. In the 4 sync boxes the top fills will be 1280 tpm and will match your current speedo. The later models had a side fill plug and no dip stick on the top of the case. Those transmissions are 1000 tpm and will result in a large speedo error. If you use a 5 speed box you may need to have the speedo re-geared or get a ratio adapter to match the output of the transmission to the speedo.
 
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