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Triumph Overdrive Transmissions TR6 /GT6

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Pat Ledford

Triumph Overdrive Transmissions TR6 /GT6
« on: February 16, 2016, 04:48:25 PM »
I am not positive but I think I am right on this, TR3,TR4,4A, GT6,

Spitfire, 250 and early TR6 used the "A" overdrive.  Late TR6's used a J

overdrive.  A Volvo J overdrive will work also if you change the propshaft

flange.  I think the Stag used an "A" od and it was the Stag that had the

switch on the shifter knob.  The others had a lever on the steering wheel

column.  If you are going to retro fit and want the switch on the shifter

knob, Jeremy (oppositelocksmith) on the 6-pack forum makes an wooden shift

knob with a switch embedded on the side for the OD.



*Patrick *



*1975 TR-6 CF39910U "Waldorf" Mimosa*







* Western Pennsylvania Triumph Association 6-PACKVTR TWOA*



On Tue, Feb 16, 2016 at 1:07 PM, TYA2 <tya2@4-fly.net> wrote:



> I own a 1980 TR7 with 5 speed transmission. and I am thinking of adding a

> 70 ish Triumph GT6+ to the family fleet.   I have been looking for one with

> an overdrive transmission.   The car may be a driver or a project.   Was

> the Triumph TR6 transmission with overdrive available in other cars in the

> Triumph family?   Am I looking for a phantom 45 year old car in that

> possibly there were not GT6s with overdrive?   When I was young and these

> cars were new I remember driving the TR6 with overdrive,  a switch on the

> top of the shifter knob if I remember correctly?

>

> Anyone help with my questions on this area of TR history and knowledge.

>  I am in Canada so I am definitely talking about exported to North America

> cars.

>

> Reg --

> .

> Archives provided courtesy  http://www.triumphwedgeowners.org

>

--

.

Archives provided courtesy  http://www.triumphwedgeowners.org



Steve

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #1 on: February 16, 2016, 05:45:45 PM »
Hello,

The J-type was used on the later Spitfires for sure as I have a few. These

have a cheesy slide switch in the shifter top for OD.

I have one GT6 with an A type overdrive. I think it is a 67 or 68. It was a

parts car so I can't say for sure where the switch is for it. The GT6's have a

lower rear end ratio (3.08 I think) for a higher top speed with lower RPMs so

fewer of them are OD.



Of the five GT6s I have that is the only one with the overdrive. It is also

the earliest of them as the rest are 69s and one72 or 73 with power brakes and

straight axles.

Wayne Simpson

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #2 on: February 17, 2016, 12:19:04 PM »

"Tom Eller"

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #3 on: February 17, 2016, 06:26:13 PM »
The Spitfire and the GT6 use a different o/d than the TR6.  The switch

in the shift knob was a MGB thing and only on the late ones.  All in

all every Spit or GT6 owner who does not have o/d wants it.

This makes them expensive and hard to find, you also need the main shaft

and adaptor plate to convert a 4 speed into an o/d unit.  If it was me I

would look into the Toyota 5-speed conversion.

Cheers,

Tom











    I am not positive but I think I am right on this, TR3,TR4,4A, GT6,

Russ Cooper

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #4 on: February 17, 2016, 07:39:58 PM »
Just to muddy the waters a little and it won't help you guys in the US, most

of the Triumph Dolomite Sprints had the J type o/d gearbox with the switch in

the top of the gearknob. B

Russ Cooper

--

.

Archives provided courtesy  http://www.triumphwedgeowners.org

Trevor Norris

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #5 on: February 17, 2016, 07:45:26 PM »
fyi ... As well as the Stags the Triumph 2000/2500 and Dolomite sedans used

the switch on the shifter knob.

Dave

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #6 on: February 17, 2016, 07:49:16 PM »
As did the Spitfires and GT6's.  It seems only the TR's had the dash/column mounted switches.



 



 



Dave Massey

johntrlucas@aol.com

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #7 on: February 18, 2016, 01:19:52 AM »
Hi,





I have an overdrive fitted to my 4 speed TR7, its a single rail gearbox with a J type overdrive unit out of a Dolomite 1850, not a Sprint as this used a different gearbox and places the lever in a far from ideal place. The same single rail box was also fitted to later Spitfires to replace the earlier 3 rail box box, which was also fitted to GT6's.





Cheers John

kddpowercentre

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #8 on: February 18, 2016, 04:33:23 AM »
John



Reading

http://www.quillertriumph.co.uk/Quiller/Parts/gearboxesnewandused.htm

site they quote #1550 for conversion kit, how complex was your TR7 fix.



I prefer the 4 speed, so overdrive is my option for white 7, when I had

it in 1980 it ran out of revs at 108mph on the clock, having overdrive

should give us a bit more, as bhp was not a limiting factor back then.



In passing my mate ran a 2.7 litre fuel injected  straight 6 in his

Triumph Vitesse with overdrive, so may be another option for overdrive unit.



Brian



77 TR7 4sp

77 TR7 5sp

--

.

Archives provided courtesy  http://www.triumphwedgeowners.org

johntrlucas@aol.com

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #9 on: February 18, 2016, 02:03:36 PM »
Hi Brian,





Conversion reasonably straight forward, in basic it goes something like this -





As I said I used a Dolly 1850 O/D box, same box as a 7 but with a J type overdrive on the back. Personally rebuilt the box and as anyone who have rebuilt a 4 speeder its simple to do.





A custom propshaft is required as the box is naturally longer, the wiring on the gearbox plugs straight into the TR's loom and uses the feed for the reverse light switch to power all the O/D electric, uses very little amperage as after all its only a hydraulic pressure that's being switched via a control valve.





You also need to space the box down a little as the remote sits slightly higher, I used a spacer between the cross member and the floor.





Maybe I should do a short few words for the magazine ?





The conversion was offered by Coombes Of Guildford over here back in the day before and after the 5 speed was made and have a old magazine test of one of there cars.





Drives really nice with 3rd overdrive is basically same as direct drive 4th (  0.966 ) but you dont need the clutch to basically go 3rd to effective 4th, the overdrive is 0.797 so knocks the revs down.





Can email you picture if you want ?





Cheers John

kddpowercentre

Re: Triumph Overdrive Transmissions TR6 /GT6
« Reply #10 on: February 18, 2016, 03:45:44 PM »
Hi John



Photo would be nice, I have to get the white one sorted and like the o/d

option.



Will have to find a new home for the 5 speed TR7, just do not have the

time to sort. It's a shame to part it out as it is a UK Speke 5 speed

and from what I read only one batch were built for the UK market.



Brian



77 TR7 4sp

77 TR7 5sp