Which overdrive unit ?

[1904vitesse]

I have just purchased a gt6 with non overdrive, if i want to put an overdrive unit in is there a choice of units to use.

The gt6 is a mk3. Any help would be appreciated. 

[Clive]

All gt6 and vitesse used the d type OD, and it is not an issue at all.

 

Eary Dolomite 1850 used the same 3 rail gearbox, but fitted with a j type od which is  stronger. However, I have never damaged or had to work on any of my d types over the years (but one j type needed a cone clutch) so either will be fine.

 

Be carefu you do not get an early vitesse 1600 setup. It will fit. But avoid them, only 3 synchro and weaker gearbox. Late GT6 slightly stronger box IIRC but not really significant.

[1904vitesse]

Thanks for the reply, are there any modifications needed if a j type box was fitted instead of a d type.

[Clive]

Not if it is a dolly 1850 3 rail box (most dolly 1850 had the later single rail box, different animal)

 

I assume you know about the rest of the conversion parts 

 

shorter prop, od gearstick or column switch, od wiring (j type simpler but d type not hard), Metal gearbox mounting plate and rubber mount, speedo cable and angle drive

 

wort noting diff ratios too......(od 3.27, non od 3.89) but the overall top gear is identical. Personally I would have OD with a 3.63, but 3.27 would be good for cruising at speed.

[Cookie]

Just to be clear, you can't just bolt an overdrive on to the back of your existing gearbox....   The gearbox has a different output shaft, and would also need the adaptor casting. Your best bet is to find a gearbox and overdrive assembly complete to be honest.

 

There are a few uprated GT6 gearboxes about with J type overdrives fitted, they were not a standard factory offering but were sold by suppliers such as canley Classics as an upgrade. I don't think there is anyone selling these now but occaisionally 2nd hand ones come up for sale.

 

Canley Classics also used to sell overdrive conversion kits with all the parts needed, However they only seem to do these for Spitfires and Heralds now. However a look at their web page picture of the kit gives a good indiactioon of all the parts required. Gearbox and od, mounting plate, od gearbox mount, od wiring loom, propshaft gear knob with switch, od inhibitor switch etc. Quie a few parts to be honest.    http://www.canleyclassics.com/overdrive-conversion-kit/

[Clive]

Good point Andy. Re reading the OP it does seem Mr 1904 may think that!

 

But I have an early dolly 1850 OD box here, and it is identical to a GT6 except it is J type. A sought after box I believe (and hope!)

[Cookie]

Clive,

 

 

I reckon it would have been the output shaft from the Dolly box and the adaptor plate that would have been used to build the J type GT6 upgrades offered by the likes of Canley Classics (or many years ago Kingston Sportscars!).

 

I think a Dolly 1850 box would have diffferent rations but would still fit and be useful. GT6s and Vitesses alledgedly had "close ratio" boxes.

[Clive]

Not so sure, I think they are the same ratio. I know the dolly 1850's all had very long first gears, but at the mo can't find the detail. I would put a pound on them being the same.....

[1904vitesse]

Thanks for the replys guys, have bought an overdrive d type gearbox along with the drive shaft from a 2ltr vitesse. I also have another shorter driveshaft from a gt6

i will pick up the other bits i need when i start the restoration. This is likely to be a while as i have the vitesse convertible to get finished first and then it will be a choice between which of the gt6s i get done.