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Overdrive Conversion - What parts are needed?

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Car is a bitsa.  2000 ME engine, GT6 Chassis, Spitfire body.  Possibly toledo gearbox, but not sure.

60 mph comes up at just over 4000 RPM which isn't great for long journeys so seriously thinking about OD conversion.

I'd do this myself / help from Shropshire TSSC's hit squad.

My aim is to accumulate all the parts and make a day of it rather than have the car off the road for ages.

I'm seeking advice on the parts I'll need and likely issues.... this is a well trodden path after-all!

My list so far - 

  • Reconditioned OD Gearbox (prefer this to unknown SH unit)
  • Shortened prop shaft (I'll get a SH unit and check / replace moving parts myself)
  • Speedo angle drive
  • Mounts / rubbers
  • Gearstick with switch
  • Gaskets
  • Wire / connectors etc.

Anything missing?

Am I right in thinking the d-type will be compatible with the existing bell-housing?

Anything else worth doing at the same time?

Thanks for the help folks.


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OD has no effect on the clutch housing  , is the toledo box a 3 rail ?

Needs the od to gearbox adaptor housing.

You, need the od rear mount and chassis plate amd a gearchange  remote with a cam to operate the inhibitor switch

You need to cut 5" off the prop tunnel and make a cover to get at  the  prop coupling .

7/16" washer to fit inside the angle drive.

Why not change the mainshaft in your current box if its ok



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Toledo box is the same as Mk4 Spitfire, up until extremely late (in fact I'm not sure the single rail made it on until the Toledo was discontinued in favour of the Dolomite 1300)

60mph at 4000RPM sounds like you still have a 4.11 diff. A 2L Spitfire really wants a 3.63 even with overdrive.

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Yes, check the diff ratio, as that can cause misery. And have you checked Speedo accuracy against a satnag?

Don't think it will be a Toledo box, the 4 cylinder box doesn't work with a six engine, as in clutch etc etc. Probably a non od box office a Vitesse/gt6. Visually very similar, but input shaft is longer and bigger clutch splines. Better gearing too.

I think you have got the list now. I would hesitate to chop a prop, they can cause untold issues with vibration. Unlike me, but it is something I would likely buy new from Dave Mac. 

And in the scale of things, buying a recon box/od is hardly cheap. Tony Lindsay Dean was selling some very good ones on eBay at sensible costs, about £800 I think but the components meant they were excellent value. 

Overdrives tend to be reliable. If you have a good box, you could buy a short of conversation, and get somebody to check it over, possibly cannabalise your existing box for spares. Just a thought, we have a local who is rather good at that sort of thing.

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Cheers folks.

I'll swap the diff first them and see what difference that makes.

I can get hold of a recon OD for £625 (no exchange).  I've had the car 18 years and not planning to get rid in the near future so seems job worth doing.  But if I can achieve the desired result with a new diff then worth trying first.

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Importantly, please check speedometer accuracy first. In all honesty I would prefer od to longer diff as you retain the better overall gearing. But depending on what diff is currently fitted of course. If you have a 3.89 it would be gt6/Vitesse od ratio, and a good ratio with od added. 

Shame about my diff, checked over with all new seals fitted etc I sold it for about 1/3rd what you have been quoted.


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Looks like Fitchetts (15 mins from here) have a 3.63:1 diff for £360 incl £100 surcharge so £260 if they'll accept my old one in exchange.  Not sure if this includes VAT but either way worth a go.  My diff does have a perpetual leak anyway (have jiggled the breather and not that).

The speedo isn't that far off against sat nav at higher speeds.

I've just signed up for a 1600 mile road rally next year so I'm going to need a better cruising gear  https://www.4ballr.com/


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  • 3 weeks later...

Hello everybody, On the subject of overdrive does anyone have a clue how to wire a j type? I have a mk2 Vitesse 2lt and its been apart for so long that I cant remember how it's wired. Thought I'd taken pictures of it but if I did I can't find them. (Doh!). Unfortunately I'm not a sparktrician and don't want any extra heating in my car (ie; unwanted flames) so any help would be greatly appreciated, preferably with coloured diagrams the size of the car to make it easy for me to follow. There was no relay fitted before and the overdrive worked perfectly so I don't really want to fit one now. Thanks in anticipation, Rob.                                                                                                                                                                                                                                                           P.S. Sorry if this request is in the wrong section of the forum but I'm not very good at this sort of thing either

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J type does not need a relay ,,, unless you want to fit one the current is only abot 0.5amps,   no heating or flames 

You need a ignition fused supply to the gear knob switch  you can run the feed via the 3rd 4th inhibitor switch to the solenoid and add an earth to the solenoid

Or run the switch feed to the solenoid and run the  sol terminal earth through the inhibitor .



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As this is a Vitesse we're discussing, the switch should not be on the gear knob but on the steering column.

Three wires needed:

- from fused ignition switched (green) to the column switch

- from the other side of the column switch to the inhibitor switch on the gearbox

- from the other side of the inhibitor switch to the solenoid.

On mine, I did add a relay because, while the J-type solenoid doesn't draw huge current, it does have huge inductance and causes arcing on switch off. A relay is much cheaper to replace than the column switch. Actually, I also added a diode to protect it, but none of that is strictly needed. The intermittent fault that set me off on that track was actually a chafed wire because the PO had trapped it in the column cowl.

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My Vitesse didn't originally have an O/d, but I couldn't be ****** to fit the column switch, and the gearknob one is failure prone.     I fitted a Press on - Press off switch to the the steering wheel, supplied by a length of curly-whirly cable, in the style of  rally cars with flappy paddle gear changers.     Even got an LED to monitor it. 



Wheel mounted O-drive switch.jpg

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