The Triumph Dolomite Club - Discussion Forum

In the past I have heard of GT6 and Vitesse buying Dolomite (1850) three rail gearboxes for their cars.

Five speed conversions like THIS ONE are available for GT6 models.
I guess this uses the GT6 bellhousing?
If so, I wonder if it is possible to use an 1850 bellhousing to allow the Ford five speed to fit a Dolomite 1850 or Sprint ?

Obviously it would need a bespoke propshaft but in the overall scheme that is no' a big hurdle .

Hmm at that price you could have another whole dolomite.

Why would u bother when the 3 rail with o/d is very nice.

not that an 1850 needs o/d that much around town anyway.

Jonners

From memory I think the GT6 gearbox is much more like the Sprint gearbox than the 1850.
Julian ( TinWeevil ) would know better than me.
5-speed box..... not sure.
1850 single rail box + overdrive is a very nice combination for all road conditions.
Cheers All,
Tony.

IIRC the Sprint gearbox is too big to get between the GT6/Vitesse frame rails, the largest that will fit is the single/three rail box.

1850 three rail 'boxes highly sought after by GT6 and Vitesse folk; there was a guy in Ledbury who did the necessary alterations to make them fit a few years back and used to pay £170 unseen for them. I bought two scrappers once based on the fact he would; basically I ended up with the rest of the car and transport costs covered for free both times!

I'll post picks of both over the weekend if there's any difference in the bell housing, the box itself certainly is identical (ratios?).

Interesting question Ian, I've wondered whether the same conversion would fit in in an OHV 'mite since it will go in a Spit. The attraction for me would be reduced weight. Iron bell + iron box + O/D is a very heavy lump. The same box without O/D is significantly lighter. Take that lighter box and make the bell and casing alloy, all be it with a bit more inside, and there's going to be even more weight saving.

Wouldn't a TR7 5 speed be a more straight forward way to get the same result in an 1850 though?

[edit]D'oh! LT77 casing is iron.[/edit]

DavePoth wrote:IIRC the Sprint gearbox is too big to get between the GT6/Vitesse frame rails, the largest that will fit is the single/three rail box.

Nope, I and others have fitted the saloon boxes (same as sprint except shorter input shaft) to Vitesses, GT6's etc. Just a bit of faff.

As to why dolly boxes are used in GT6. Simple, it has the J type OD as opposed to the d type.
But the actual gearbox casing is the same, so no reason why you cannot use the adaptor plates to fit a T9 to a dolly bellhousing. I will muddy the waters here though.
A engineer on teh CT forum ran into problems. Firstly the adaptor plate needed faffing with to fit the GT6 9and therefore dolly) bellhousing, as they are aimed at the 4 cylinder cars really. Not a big issue though.
Secondly, you need a T9 with the long input shaft. It may need reducing in length slightly too (angle grinder!)

Julian, the T9 boxes are not light. Iron case Plus you use your existing bellhousing. Simpler solution may be an alloy bellhousing from an early herald, saves a lot of weight (but don't be tempted by the herald all alloy box)
I'll weigh a T9 in a bit, sans bellhousing.

I've seen a GT6 box with J-type o/d in a blokes garage. It looked identical to the one in my dolly. Alloy bell housing and clutch slave location were identical as was the clutch spline count on the input shaft. No I know this wanst a side by side comaprison and I dont have a GT6 parts book to hand but I couldn't see much different from the Rimmers web site last time I looked.

The box internals single to 3 rail and bell hosuing are very similar too...in fact most of the gears are interchangeable.

You could indeed put a TR7 6 speeder behind a slant 4 and its been done several times. The difficulty here is the slave cylinder operation. Some have modified to suit the Sprint type cross shaft mechanism and someone used a clucth cable. Alan has one on the quicksprint I think.

My experience with 3 rail boxes behind more powerful Triumph lumps is mixed. I think they are marginal, which is why Triumph themselves engineered the large car box to fit the Sprint.

If you want to spend the thick end of 1500 quid on a ford box for a car thats a hard sell at 2k in good nick then thats up to you. I prefer the cheaper original options....and it seems to me that supply and reconabilty isn't too bad in that department as yet.

An alloy bellhousing for spits is the way to go and they do come up occasionally as I agree the cast iron setup is a bit of a lump.

Jonners

I am not certain the GT6 boxes ever had j-type OD. But indeed many have had the dolly box retro-fitted over the years.
Kippings used to do a fair bit of trade selling gt6 od boxes, I think they had mainshafts made and so on, so plenty about.
The boxes are OK on 2 litre and indeed 2.5 litre cars if treated with a little respect. Other gearboxes are stronger though. But always more grief to fit.
Type 9 conversion should be way less than 1500. Secondhand boxes fetch sub £100 and generally pretty good. Just the adaptor plate, faff about with the clutch (late dolly 1850 for GT6, custom one for a spit unless you can find something that will fit, must be something out there) then a propshaft. The rest is monkeying about with mounts, speedo cables and so on. Probably do-able for £500-600. Not a lot different to a good OD setup. And have a peek at how much a complete recon od conversion costs thesedays. Getting on for £1500 And which box will last the longest

If I hadn't spent the thick end of £300 on a custom propshaft to suit the five speed 'box, or had opportunity to drive it on the track before the need for the custom prop developed, the quicksprint would have been back to sprint 4 speed with overdrive on 2,3 & 4 now!

cliftyhanger wrote: Probably do-able for £500-600. Not a lot different to a good OD setup.

We are thinking the same.


I know the type 9 is an excellent gearbox, capable of huge mileages, because my brother had a Sierra 1800 in the
90s when he worked as an insurance rep. (That car however had a terrible habit of destroying rotor arms and on at least
two occasions had to be towed home behind an HA Viva van, no less.)




Thanks for your input so far everybody.
Please keep it coming, info on weights and dimensions is appreciated .

Type 9 without bellhousing a smidge over 30kg (on the bathroom scales. And no, I didn't take the box in the bathroom!)

Thanks, a complete 1850 o/d box including bell housing weighs 42 kg so there will be a weight saving.

i'm thinking the gearlever hole would need some thought, off memory the ford is a lot further back. may not fit under the removable dolly cover.

craig

Thanks Craig, I had considered that possibility and following your reminder I have investigated
further and found that the Ford position is about 70mm further back than a GT6.
There are three options,
do nothing and have the gearstick further back,
have the gearbox remote shortened (which is what Frontline and Jigsaw do) to bring the gearstick to
the normal position,
or use a modified gearstick (a la TVR).

I favour the last option from what I have seen.


Just looking at this stage.
First I need to find a Sierra 'box and prop.........