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overdrive surprise

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overdrive surprise
#1
  This topic is about my 1970 Triumph GT6+ (MkII)
GerryV8 Silver Member Gerry Reis
Brantford, ON, Canada   CAN
I bought my GT6+ in November 2017. It is the first Triumph I have ever owned so I am learning as I go. I am in the process of fixing the sloppy shift lever. Many thanks to this forum for explaining the steps to accomplish this. Once I got the tunnel off, I found an overdrive unit. Surprise!! The previous owner told me it did not have this. My research into the commission number suggests it was not on the car originally. So, a couple questions... how can I tell if the transmission was replaced along with the addition of the od unit. If the transmission did not originally have an od unit, will I find a 3rd 4th switch to control the od? Where do I look? Is there an easy way to tell the rear end final drive ratio , I know they were different on od/non-od cars.

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Born Loser Avatar
Born Loser Silver Member Matthew Taylor
Land O Lake, FL, USA   USA
Holy Crap!!! What a find!

In reply to # 1509004 by GerryV8 My research into the commission number suggests it was not on the car originally.
The Commission number would simply have an "O" at the end, if it was original.

In reply to # 1509004 by GerryV8 If the transmission did not originally have an od unit, will I find a 3rd 4th switch to control the od? Where do I look?
If it was added, it could be anywhere. The switch just needs to be a regular (on or off) switch - so toggle, mounted on the dash, would probably be the easiest.


In reply to # 1509004 by GerryV8 Is there an easy way to tell the rear end final drive ratio , I know they were different on od/non-od cars.

Here is how I would do it - just jack up the car, get both rear wheels airborne. Chalk a line on a tire at exactly 12:00. Have a helper watch it. Crawl under the car, and chalk an alignment mark on the drive shaft flange - to something stationary, like the differential housing. Now, with the car in nuetrol, have the guy at the tire slowly rotate it one full turn, back to 12:00. While he is doing that, you watch the mark on the shaft. It should go around at least 3 times, possibly 4. Thats your fist number. Next, guess how far toward (or away) from the line it ended up. About 1/4, that's going to be a 3:27. Just short of 1/10 of the way to 4 - thats a 3:89. A bit past 4? Thats a 4:11.



Matthew
1960 Triumph TR3a
1970 Triumph Spitfire MK 3
2012 Mini Cooper SS Convertible
2018 Jaguar F-Pace

Fictioneer Avatar
Fictioneer Doug Hirt
Colorado Springs, CO, USA   USA
Nice surprise. Congratulations. If it was added later, the switch could be anywhere, as Matthew said. If it were mine, I'd locate the switch on the steering column. If it doesn't already have an OD Plinth, they are cheap to buy, and a proper OD switch from the usual suspects will run about $40.00. But really, and SPST switch will work.



"Mr. Filby, do you think he'll ever return?"
"One cannot choose but wonder. You see . . . he has all the time in the world!"

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colodad Avatar
colodad Silver Member Calvin Williams
Grand Junction, CO, USA   USA
Is the solenoid wired into the system?
Is the safety switch mounted forward on top of the transmission plate?
if so the power wire could be traced to the in'out switch.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I assume this is a 'D' type which must be controlled via a relay!

GerryV8 Silver Member Gerry Reis
Brantford, ON, Canada   CAN
The switch I was wondering about is probably somewhere on the transmission and it would limit the overdrive to engage only when the car is in either 3rd or 4th gear. The on/off switch would be wired in series with this.
The commission number has an L, that is what has me wondering about the 3rd 4th limiter switch.

the od is a D type

the power line is broken and hanging... when I hot wire it, I can hear it click.

Stanpart casting numbers 303250 and 88306468 and 30M1



Edited 3 time(s). Last edit at 2018-01-22 01:34 PM by GerryV8.

teeka56 Avatar
teeka56 mike leisner
Seattle, WA, USA   USA
The control switches are activated by the shifter. On the engine side of the shift controls. If you have the tunnel cover off they should be easy to see and test. Be sure to use them to avoid the fatal OD in reverse possibility.

Enjoy, mike

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TheBomb Avatar
TheBomb Chris Gill
Toronto, ON, Canada   CAN
1975 Triumph Spitfire 1500 "The Bomb"
I wish I found that kind of surprise on our spitfire. Cheers on your good fortune. smiling smiley

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
Lucas felt switches inline should be designed to turn off the OD more than turn it on.

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GerryV8 Silver Member Gerry Reis
Brantford, ON, Canada   CAN
I see only 1 switch on top of the transmission under the shift rod housing... I suspect it is the reverse light switch

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
There should be an inhibitor switch on the end of the gear selector extension.
Top right hand corner of pic.


Attachments:
GRID005690.jpg    63.5 KB
GRID005690.jpg

Born Loser Avatar
Born Loser Silver Member Matthew Taylor
Land O Lake, FL, USA   USA
1st and 2nd wont hurt it at all. Reverse of course will kill it. If there is no switch for reverse, you need to add one



Matthew
1960 Triumph TR3a
1970 Triumph Spitfire MK 3
2012 Mini Cooper SS Convertible
2018 Jaguar F-Pace

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
Conversions usually consist of OD with the tranny included.

The Brits are fond of having different numbers for everything but they left notes. Someone might have a link to see if your Tranny was built with an OD or not.

GerryV8 Silver Member Gerry Reis
Brantford, ON, Canada   CAN
I do not see anything like the switch in the pic Tony provided (thanks Tony) Worst case, I will use the reverse switch to wire a relay that inhibits the od when reverse is selected .. thanks Matthew and Mike, valuable advice that I will take.



Edited 1 time(s). Last edit at 2018-01-22 05:09 PM by GerryV8.

teeka56 Avatar
teeka56 mike leisner
Seattle, WA, USA   USA
Is this a J type or D type? Should be a plate on the side with model.

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