overdrive Idenity.................

[TrustNo1]

Evening follow Dolomiters I have acquired an J type Overdrive with the serial number 25/115869 004966. Can any confirm what car or gearbox this would fit, some research seems to suggest it is a Dolomite 1850 unit, and is there any way of testing it?

If I can work out how to get pics fro my phone onto this page i'll post some pics later.

[yorkshire_spam]

I'm not 100% sure, but I think the tail extension and the "adapter" sections identify which gearbox/vehicle the OD mates to. (Which is how you can fit a P-type to a GT6/Spitfire for example)

The 25 is the % reduction (so it's a 25% overdrive)

Next bit is the "type", which I think are:
115876 TR6,
115835 Large saloon
115868 Dolomite 1500
115869 GT6

Maybe GT6/1850 are the same type? See also... http://www.buckeyetriumphs.org/technica ... 1/JOD1.htm
Cheers, Sam

[tony g]

25/ 115842 is on my Sprint O/D so is that Sprint specific?

Tony

[Mad Mart]

I've just had a look at a couple I have, they both have 25/115842 and are both off of Sprints.

[xvivalve]

Richard Old published some info in one of the more recent Dolly Mixtures on overdrive identity, but of course, that's the issue I can't find!!

From memory the first two figures is the % reduction, the next six identify the make/model, the remaining ones are the serial number of the unit...

[Galileo]

Agreed.

viewtopic.php?f=4&t=33020&#p306413

[tony g]

I've just had a look at a couple I have, they both have 25/115842 and are both off of Sprints.

Yes I found more reference since I posted and thats definitely the Sprint number. I wonder what the difference was from the big 6 cars with J type is then? Ratio maybe?. Our boxes are basically the same as the 6's (Input shaft length differing)

Tony

[TrustNo1]

Thanks for the replies, anyone want a GT6 O/D unit?

[Carledo]

If it's a GT6 unit, it will fit an 1850 gearbox, also Vitesse 2.0 of course and probably 4 speed TR7 as well since the gearbox adaptor plate and mainshaft are the same for all those models.

Steve

[xvivalve]

I expect a GT6 unit to be sought after.

Think yourself lucky, I'm trying to identify a J type rescued from Jonners's garage, it's a 28/115872 which so far I've narrowed down to possibly Healey (good) or Volvo (less good)!

So '115' doesn't necessarily stand for Triumph

[Carledo]

I expect a GT6 unit to be sought after.

Think yourself lucky, I'm trying to identify a J type rescued from Jonners's garage, it's a 28/115872 which so far I've narrowed down to possibly Healey (good) or Volvo (less good)!

So '115' doesn't necessarily stand for Triumph

If it's a J type, it wont be a (big) Healey as they stopped making them before the J type was invented.

Had a couple of Volvos with o/d but can't remember the codes, if I ever knew them!

Steve

[tony g]

I expect a GT6 unit to be sought after.

Think yourself lucky, I'm trying to identify a J type rescued from Jonners's garage, it's a 28/115872 which so far I've narrowed down to possibly Healey (good) or Volvo (less good)!

So '115' doesn't necessarily stand for Triumph

Sure its not a Stag Al?

Tony

[TrustNo1]

I expect a GT6 unit to be sought after.

Think yourself lucky, I'm trying to identify a J type rescued from Jonners's garage, it's a 28/115872 which so far I've narrowed down to possibly Healey (good) or Volvo (less good)!

So '115' doesn't necessarily stand for Triumph

115873 is Volvo 1800 according to a chap on one of the Volvo pages Alun.not much help but its close.

[Richard the old one]

I thought that I had posted this yesterday but I can’t see it so it could be anywhere on the board I am afraid.

We are all in agreement that the first two numbers are the reduction ratio and that the next group of six identify the specific type of car that the O/D has been built to be fitted on. The only things that can vary between specific cars I believe are the speedo drive as this is determined by the rear axle ratio and the size of the wheels. This is why there are two build standards allocated for the 1500 dolomite as there was a change in rear axle ratio during the build of the 1500. I have also read that there may be a difference in operating pressure between models but I believe this is achieved by adjusting the relief valve which would not seem to be too difficult to do. The outcome I think is that provided the reduction ratio is the same as what you need the cost of getting the speedo drive gear changed and the pressure altered should not be too expensive.
If the O/D comes with an adaptor plate and a prop shaft coupling flange there would also be a need to check that these are the same as on the car to which it is to be fitted.

[TrustNo1]

Thank you Richard.