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MG MGB GT V8 Factory Originals Technical - 5 speed for stock engine

I am looking into changing the 4 speed out of my otherwise stock 65 b. I would apreciate suggestions as to the best 5 speed kit and kit providers.
Don Thorpe
Don Thorpe

V8 or not?

original 4.
Don Thorpe

Hmm, the one thing I'll miss about my stock GT is the original 4 speed plus overdrive. Very neat to flip the stalk (opposite the high beam dip to drop down to fourth and then flip it back into fifth.

As you have the original engine why not go with an original option. I'm sure you could find the overdrive box and shorter driveshaft cheap.

Beauty is, it bolts right up.
(unless of course it wasn't offered in 65, but I seem to recall an early and then later overdrive unit so I suspect it will work)


Brian C.
Brian Corrigan


As you have the original engine why not go with an original option. I'm sure you could find the overdrive box and shorter driveshaft cheap.

Unfortunately, this is no longer the case. Working overdrives can cost you an arm an a leg.

In my OPINION, the overdrive in the MGB is vastly overrated. These engines were made for high's just our ears are now accustomed to hearing much lower revs (2300-2800) at highway speeds.

TO each his/her own.

1978 MGB
1969 MGC
1974.5 MNG/GT V8 conversion
rick ingram

I have a overdrive box out of a 1972 B Roadster it is complete and working I also have the prop shaft and the clutch arm and slave cylender it is all for sale if You are interested You can also have the wirering harness and switch
p Dorner

Perhaps this is not the place, but it seem to be the right time, Sorry! but here it goes.

I will be converting a 74 CB It has a new high compression engine with a kent cam and a down draft Weber carb, electronic ignition, and a rebuilt over drive trans.
both will go on sale, anyone in Ca who is interested and would like to drive the car, just let me know.
engine has 5000 miles same on trans.
Bill Guzman

Don, i have no suggestions at this time but since the subject is open we have a prototype bell housing that fits the 4 cylinder and uses a Ford T5 or a GM T5 and uses a hydraulic throw out bearing. We are still looking for a casting company that can produce them at a reasonable cost. Hopefully we can beat the cost of an overdrive installation or match the cost of the present available conversions. Keep in touch if you wish.

Dann BCC
Dann Wade

I'm with Rick. You don't NEED it.

The MGB overdrive only makes about a 500 rpm difference. I had one in my '79 MG before it became a V8. My Dad keeps talking about putting an overdrive in his '63 MGB. I say "what for?" He's enjoyed it for 40 years without the overdrive. The Interstate is no fun any way.

I drove my Dad's '63 B to the 2000 MGV8 Event in Cleveland, OH. It took 8 1/2 hours to get there. Top down all the way up and back. The tach sat on 4200-4300 rpm the whole trip. Got 27 miles per gallon.

You don't need an overdrive, but in this section of the MG Enthusiasts Board we believe it's your car and you can do to it whatever you wish.

P.S. There is lots of help on this subject in the archives.

Jeff Dellow in Sydney Australia makes a variety of Kits for the toyota supra gear box. One of these is MG.
He ships all over the world. The supra box is very good, very smooth, about 25kg less in weight than the MG box and very strong. Various other cheaper Toyota boxes will fit the kit, corrola etc. He can sell you a reco supra box ($650 australian)if you really need but it's far more likly you can get one for next to nothing local to you and no shipping costs.
The bell housing, tail folk etc is around 300 australian, about 150 US I guess. His contact details are in the archives (just search for supra gearbox) along with a ton of other info. If you can't find his phone no. let me know and I'll look it up next time I'm near a computer (3 or 4 days). Obviously I bought the set up for the V8 and am not up on details for the 1800 kit so there may be more than one clutch slave set up, if there is keep in mind the MG slave is 1.25 inch, and the supra slave is 0.75 inch so if you have the option get as close to the MG as you can, although I would expect/guess the MG slave should bolt on.
The W58 gear box has a 5th gear ratio of 0.78 which suits the V8 conversion but might be too tall for the std 1800 motor, the W55 is around 0.82 (I think).
There are 4 ratio set ups to choose from.
There are 4 gear box lengths to choose from, d, the longest is the one you want. Jeff will Fax you information.
One thing to be wary of is that the MGB gear lever has a 14mm offset to the LHS, which the supra (and most others) obviously don't. I got around this by having the back of the box as high as possible so that the gear lever doesn't interfer with the transmission tunnel or V.V.

Obviously its the box I use, and I like it

The Owners Club worked up a kit incorporating a ford box- also used in the Sierra - as I recall. There is not a lot of demand because it is so easy to get a good secondhand OE box in UK.

The only reason for changing here is to cope with a lot more torque. The OE box will cope adequately with the 110 BHP which you can get from tuned early engines.



I think your pricing may be a bit out. I have a quote from Jeff to replace the gear box in my 1800 B. $750 for a reconditioned Celica 5 speed box plus $915 for bell housing, pilot bush, pivot bracket, clutch plate, cross member,speedo cable tail shaft yoke & speedo drive angle.

Still a lot cheaper than many overseas quotes I have seen.




My wife and I drove to the AMGBA meet in Titsville, Florida this past Saturday in our 4 clinder '66 B, a trip of about 120 miles one-way. We averaged 80-90 MPH on most of the interstate miles except for part of the return leg where we travelled with fellow club members in an A and a ZB Magnette among others. Without the old D-type OD the trip would have been a lot slower or a lot noisier. Tooling around country lanes without OD is fine, but at freeway speed it sure is nice.

Uhhh.... Titusville. I guess it's a subconcious thing.

Must have gone up a bit I guess since last year (or maybe he just liked me!). I expect the cross member and plate would add a bit though or maybe he charges more for the 1800 bell housing etc., which would make sence as reco-ing an o'drive box would be about $2000 I expect/guess, and he would be aiming to keep his price just a little under that.
Don, not to be a wet blanket but it's a lot of work to swap gearboxes about, you would have to have a tail shaft made up as well. Going by Grahams remarks you would be looking at about $500 US to get the bell housing etc to you then (locally) drive shaft and gear box on top of that (maybe $400 US). Essentially unless you enjoy doing this sort of thing it might not be worth the effort.
However, if you're determined then get Jeff to send you a FAX. He breaks down the kit to individual priced items so you can pick and choose. For example, were I buying again I would only get the bell housing,yoke, bush and fork from him and sourse the other gear else where.


First of all, while some may argue that overdrive doesn't help your engine, it sure DOES help the driver! Along about 3500 rpm, I get tired of listening to a revving B engine. Around 3600, I start getting annoyed. 3500 is only about 63 mph, so one doesn't have to drive the interstates to benefit. My "new" 74 B/GT does not have overdrive, but I've got one for it and you can bet it's going in as soon as I have the time to do it! I put one in my '73 Tourer before we drove it 1200 miles to Minnesota for MG2001. Sure I prefer to stay off the interstates, but it's nice to know I can keep up without the engine screaming if I have to.

But, your '65 has a narrower transmission tunnel than the '68 and later models; it won't accommodate a 4-syncro overdrive tranny without the generous application of a BFH to the tunnel first. Your alternative then is a 3-sync overdrive - which was available for the '65 B and it will fit. The trick is to find a good one for less than an arm and a leg. I have a '65 in restoration, and after several years of looking, I finally found a 3-sync o/d tranny. I still don't know if it's any good or not, but at least I have one.

So, if you can't find a 3-sync o/d and you don't want to bash out the tunnel to fit the later 4-sync o/d, your solution is a 5-speed conversion and there are three conversion kits available.

1. The Ford Sierra conversion sold by Butch White in Anderson SC.

2. The Datsun 280Z conversion sold by Novus in CA

3. The Datsun 280Z conversion sold by Rivergate Restoration Products in Soddy-Daisy Tennessee.

I installed the Rivergate conversion, along with a 5-main 18GB engine, in my Magnette, and I cannot rave enough about it. We drove the Magnette cross country (6500 miles) at speeds up to 80 mph - which would have been cruel and unusual punishment in a stock Magnette.

The Rivergate conversion is thoughtfully engineered and beautifully built. It's as easy to install as a stock B tranny and you'll love it.
Allen Bachelder

This thread was discussed between 19/09/2003 and 24/09/2003

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