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6-speed tranny for MGB's

Posted by Starbuck 
Starbuck Avatar
Monte johnjulio
Greensboro, North Carolina, USA   usa
1967 MG MGB GT "Toaster"
1974 MG MGB "The B"
1979 Triumph Spitfire 1500 "Shitfire"

I was just wondering if there were any 6-speed conversions kits available for MG's or at least which 6-speeds would be the right size to fit in a B?

I am considering doing the Rivergate 5-speed but I wanted to know if anybody here has ever attempted to put a 6-speed in a B.

Not too kosher for an MG I know, but when mine gets to be a daily driver again at least 80% of the miles travelled will be on 70-mph highways and I think that a 6-speed would make that a lot easier.



"...They say that a man with two restoration projects is a poor man...I now have three...WTF was I thinking!?!?!?!?!?!?!"

1967 MGB-GT,1979 MGB roadster, 1979 Triumph Spitfire 1500 1974 MGB Roadster (retired, giving its life to be a parts car)

My 1974 MGB restoration at: http://mgbproject.blogspot.com/
My 1979 Spitfire restoration at: http://spitfire1500project.blogspot.com/
My 1967 MGB-GT restoration at: http://mgbgtproject.blogspot.com/
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NOHOME Avatar
P P
O, Ontario, Canada   can
1967 MG MGB GT "Maggie (GT From Hell)"

Sizewise, Miata or S2000 would be the obvious choices.Your chance to blaze a new path?

I think the horrible gear ratios on the MGB are something that we can all agree on. The car never does feel real happy in any situation unless it is overdrive at 65 mph.

Pete
sshack Avatar
Steve Shack
Victoria, Canada   can

With a 4speed overdrive gearbox, 90mph is 3157rpm. How fast
do you need to go? Does your commute involve a Le Mans race?
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Derek up North Avatar
Derek Nicholson
Sherbrooke, Quebec, Canada   can
1961 MG MGA

A friend of mine who owns one of the Montreal LBC garages has mated a Honda S2000 6-speed to a 'B engine. He's waiting for a gap in his work schedule to fit it to his 'B.

I don't really see the benefit to it. Unless highly modified, to me, the 'B engine is all about torque. It's not a high revving Japanese revver that has a narrow power band. 80% 70mph highway? I'd put in an O/D and be done with it.



Edited 1 time(s). Last edit at 11/19/2008 06:19AM by Derek up North.
Gerald O Avatar
Gerald O'Docharty
Wake Forest, North Carolina, USA   usa
1978 MG MGB

sshack Wrote:
Quote: With a 4speed overdrive gearbox, 90mph is 3157rpm. How fast
do you need to go? Does your commute involve a Le Mans race?
That would be about 70mph (indicated) at that RPM on mine ('78). Still plenty low enough.


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Derek up North Avatar
Derek Nicholson
Sherbrooke, Quebec, Canada   can
1961 MG MGA

Steve's allowed to make a mistake. He posted at about 4 am local time!
B-racer Avatar
Jeff Schlemmer
Minnesota, USA   usa
1950 Willys Jeep Pickup "Ratrod"
1955 Chevrolet Thriftmaster
1958 MG magnette
1971 MG MGB "POS"
1973 MG Midget MkII   → more

Glen Towery who hits this forum onoccasion used to have a V8 conversion with a 6 speed, if I'm not mistaken. Either that or he was working on assembling one. Hopefully he'll chime in on this. I thought it was some form of Rover derivative he used, along with a 4.6L engine.



jeff@advanceddistributors.com
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JoeReed Avatar
Joe Reed
Cordova, Tennessee, USA   usa
1978 MG MGB "Kermit"

Many MGs already have a 6-speed trans....it was a factory option grinning smiley







PAMidget Avatar
Thomas Reimel
Philadelphia, USA   usa

sshack Wrote:
Quote: With a 4speed overdrive gearbox, 90mph is 3157rpm. How fast
do you need to go? Does your commute involve a Le Mans race?

Yeah, but more gears is not necessarily just about speed, but the ability to keep the ratios closer, while climbing to a low (numerically high ratio)--the less torque available, the more closely spaced gears you want--think 10- or 15-, or 18-speed bike.
Tim Baxter
Kansas City, USA   usa

But here's the real question: what six-speed? The most obvious choice would be the Miata six, but that would be a big step backwards. The miata six speed doesn't feel or shift nearly as nice as a B box, and it's actually geared lower than the 5-speed. I believe the S2000 box is similar.

Six speeds are mostly only good for bragging rights. I wish, in retrospect, that I'd bought a miata with a 5-speed instead of a six.
NOHOME Avatar
P P
O, Ontario, Canada   can
1967 MG MGB GT "Maggie (GT From Hell)"

Joe beat me to the correct answer. Note that all the nay-sayers advocate an overdrive transmission as the solution, in fact, a six speed transmission. Also, lets be honest, how many use the six speeds available wwith the overdrive? I found that the same applied to the sis speeds I have driven (M3 and S2000) I was more annoyed than entertained by the extra gear and the need to keep factoring it in to the equation. 1-2-3-4-6 was the new math!

Finding an MGB overdrive tranny is not a trivial matter in NA. Once you find it, it should be overhauled. If it is a three sync, it is still a weak(er) tranny that makes a horrible sounds in first. Charming and "period correct if you enjoy the sound. If it is a later unit, you are now two grand into the show and running a finiky old OD unit that baffles most people. It is not really complicated, just unknown by mechanics.

Myself, I think the Datsun swap is the laymans solution to easy cruising. Moneywise, Rivergate has priced it as equivalent to an OD conversion. For some odd reason, I THINK the gears are a better fit to the MGB powerband than the original factory choices. I have not driven the conversion so I can not speak to this as fact.

Interesting fact is that the Miata 5 speed tranny has more overdrive (o.81)than the 6 speed (0.84). The Miata used the two overdrives to get away with a taller rear gear, hence it works out. The Honda comes in at 0.81, same as the Miata 5 speed. I know the Datsun has two overdrive ratios available, and I am pretty sure that one of then is in the 0.73 range (I am getting old, memory not that great!) this would put it ahead in the relaxed highway cruiser contest if keeping the stock rear end.

I find that the MGB is happiest just under 4,000 while cruising along the highway. In Ontario, I need to be moving at 75-80 to keep up with traffic. That would put me into the Datsun tranny if I were looking for a new tranny.

Pete
purpleGT Avatar
Bud Osbourne
Pittsburgh, PA., USA   usa
1956 MG MGA 1500
1972 MG Midget MkIII
1974 MG MGB GT "The Grape"
1977 MG MGB

Starbuck Wrote:
Quote: I was just wondering if there were any 6-speed conversions kits available for MG's or at least which 6-speeds would be the right size to fit in a B?
I am considering doing the Rivergate 5-speed but I wanted to know if anybody here has ever attempted to put a 6-speed in a B.
Not too kosher for an MG I know, but when mine gets to be a daily driver again at least 80% of the miles travelled will be on 70-mph highways and I think that a 6-speed would make that a lot easier.

To me, the simplist, most cost-effective solution would be to just put an MGB overdrive transmission in it. It's pretty much a bolt-in installation. While they are not nearly as common as the non-O/D boxes, they are still not too difficult to find, and parts are still readily available for them.
The one I have in my GT I got for $300....in 1979winking smiley......with 52,000 miles on it. I just plugged it into my GT and put another 50,000 plus miles on it. When I took the car off the road, to restore, it was still working beautifully and had never given me any trouble whatsoever.
You should still be able to find a good O/D box for $800-$1200. I see them every year at Import Carlisle, for example. That's a whole lot cheaper than any other alternative, I beleive.
Bud Osbourne
bobmunch Avatar
Bob Muenchausen
PC, Oregon, USA   usa
1968 MG MGB GT "Traveler"

Ditto Peter and Bud, but with the recognition that a 5-speed tranny like the Rivergate, et al, does not involve some of the problems of the electric O/D the MG tranny has tacked onto it, things such as clutches, solenoids, etc.

The MG tranny is still a pretty sturdy unit in my experience and if one takes care to do the routine maintenance, the 'problems' I mention are not a huge factor.



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Ryan Reis Avatar
Beatrice, NE, USA   usa
1968 MG MGB

I'm all for the idea on the "gee whiz cool" basis, but in reality its not going to make driving your car any better. Like Derek said, the 'b has a wide torque range that doesn't really need close ratios to keep it "on the powerband". My OD keeps up with freeway traffic just fine. If you fit a transmission with a deeper overdrive ratio you might not use it much.



Ryan
Steve DeGroat
SC, USA   usa

I have a 5 speed in my BGT. I really do like it, but still feel the engine could pull a taller gear. I live the flat lands of SC.
I had an overdrive in a 78 B one time that hung in overdrive. I could start off just fine in overdrive first.
Now, Could I just go to a Ford 8 in. with a 3.55 gear and get along fine?
Just wanted to know if that is a option for B's. Maybe even do that instead of an overdrive trans.

Steve
Derek up North Avatar
Derek Nicholson
Sherbrooke, Quebec, Canada   can
1961 MG MGA

It's certainly an option and would also make the 'Bs low 1st gear more useful!
footster Avatar
Alonzo Foote
Texas, USA   usa
1965 MG MGB
1980 MG MGB

My daily driver, a Mazda, has a manual 6.

The advantage wouldn't come from cruising, but 1st, 2nd, and 3rd spacing being closer together.

At lower speeds if I'm concerned with performance I'm primarily in 2nd or 3rd in a B, with 1st just too low. I actually use the Mazda's 1st more than the Bs.

The B's motor pulls better in the 1500 to 2000 range than my Mazda's. Maybe more accurate to say it feels better. Probably the Mazda still a bit stronger. By 2200 RPM onward there is no comparison. But there shouldn't be.

I've always found 3rd OD and 4th too close to each other to be valuable as extra gears for driving hard. I primarily use 3OD when in slow highway traffic during rush hour, bouncing between 3rd and 3OD. If the road is open enough and accelerating, using 3rd to a higher RPM, then 4 until steading cruising and 4th OD. My occasional technic is 3rd to 55K or so, 3rdOD until cruising speed, and straight to 4OD, bypassing 4th.



John


RacerX Avatar
Gregg Hanks
Huntsville, AL, USA   usa
1969 MG MGC GT
1973 MG MGB

I have the Ford T9 conversion in my B. Couldn't be happier! It is however the close ratio gearing used in the 6-cylinder Fords. It has a taller 1st and 2nd gear that eliminates the hole in the B 2nd to 3rd ratio. And because I'm running a supercharger, the taller low gears are not an issue pulling away from a stop. So if you have a slightly hopped up motor or a supercharger, I highly recommend this transmission and gear spread!

Good Luck!






Gregg Hanks
73 MGB SC
63 MGB
69 MGC GT
70 E-Type 2+2

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cfrantz Avatar
Chris Frantz
Mississippi, USA   usa
1957 MG MGA
1964 MG MGB

bobmunch Wrote:
Quote: Ditto Peter and Bud, but with the recognition that a 5-speed tranny like the Rivergate, et al, does not involve some of the problems of the electric O/D the MG tranny has tacked onto it, things such as clutches, solenoids, etc.
The MG tranny is still a pretty sturdy unit in my experience and if one takes care to do the routine maintenance, the 'problems' I mention are not a huge factor.

Also the Datsun 5 speed is a lot lighter than the MGB 4 speed and the MGB OD would just add weight. I have been gathering up the stuff needed to put the Datsun transmission when the clutch needs replacing.
balloonist Avatar
Michael Layman
Newberg, Oregon, USA   usa

Don't know if I am doing it right or not but I spend a lot of time in 3rd and 3rd over while driving around town. Car feels good and responds to the changes between 3rd and 3rd over very nicely.

I have OD in my '68 roadster and in the '72 GT. I have had MG's w/o OD and I think it is a geat addition.

Mike
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