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MG MGB GT V8 Factory Originals Technical - rover and auto gearbox in mgbgt?

Had a quick search thru the archives but cannot find anything. Has anyone any experience on this swap? Looking especially at the gearbox tunnel area of a rubber bumper car and how much work would be needed.
I know that it will not appeal to the more sporting driver but ongoing knee surgery means an auto box may be necessary for me.
Nick Bentley


I don't know if the autobox is the same height as the 5-speed but if so, an "extension" has to be built to raise the height of the tunnel. It raises the tunnel about 45 mm. Overall dimensions are 355L x 185W x 45H. It's competely hidden by the consel once installed.

Width-wise, the 'box slides right in with no modifications.

The book "How to give your MGB V8 power" (SpeedPro series) by Roger Williams has details on page 36 and a picture of the extension on page 72 & 73.

If you like, contact me off-site and I can send you some pictures of my installation.

Simon Austin

Hi Simon
I have the book already... I even have a five speed box as well, but thanks for the reminder. I was just about to start cutting the tunnel for it but if an auto doesn't need it I may save myself a job and put an autobox in instead. I want to keep this car for a long time and I stand more chance of still being able to drive without needing a clutch in a few years!
Any idea what modifications are needed to the tunnel for a BW35 gearbox on a V8? I think the tunnels on the 4 cylinder automatic and manual are the same (not exactly sure) so just the same part as the manual car should need extending as you say. A friend has offered me an automatic Rover P5b donor car but I didn't want to buy it if there was going to be a lot of other problems to overcome.
Nick Bentley

The BW35 is quite an old box only 3spd and a bit clunky, you might like to check out Ashcroft Transmissions (Enter in your search engine) they can supply recon ZF HP22 4spd auto boxes which are current fitment on Range Rovers a far superior box and will bolt up behind any of the V8's Dont know if the bell housing is different but they can provide the information and would probably measure a box for you so you can determine whether it will fit. You would have to modify the cross member but you have to do that for the manual anyway. Please post your findings as I may have to go that route in the near future. You wont need the transfer box unless you want 4WD!

K.R Jackson

Nick the link is

K.R Jackson

Nick, I'm using a BW65 auto. It fits into the tunnel without any alteration & the mounts are the same as the Rover 5 speed box as far as I can see. The top gear is 1/1, so you need a suitable diff. ratio to compensate. The dipstick/filler tube had to be altered.The kickdown cable is easily adaptable with EFI. A bit more difficult with a holley or similar carby. The BW65/66 is a bit long in the tooth now. I've no doubt that later trans. are better, but whether they fit easily or not, I don't know. The BW35 is a very tight fit & not reccomended. Barrie E
Barrie Egerton

This thread was discussed between 05/02/2005 and 06/02/2005

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