The Triumph Dolomite Club - Discussion Forum

Hi folks, I was looking into upgrading the driveline of my 1850 in anticipation for a future engine swap. I belive sprint box can be fitted with correct modifications to the subframe but what about the axle? also has anyone fitted the engine, 5spd box and axle from a tr7? I've seen a few with the tr7 engine but i don't know how dificult it would be to use the box and axle as well, or if it's even possible. my plan in the future is to fit an alfa romeo twinspark(8valve) but looking to upgrade driveline first as my axle whines and my overdrive box is a bit ropey but I thought the tr7 engine and bits would be a nice easy start.
any advice is much appreciated.
Paul.

TR7 5spd can be made to fit, not exactly easy though. Xvivalve has one in one of his. I imagine it'll want the same sort of adjustments as the Sprint box.

If you go for the sprint box you want to adjust the subframe to get the engine in the same orientation as the sprint engine, so that the gearstick is in the right place. The rear axle is a straight swap.

The TR7 box is shorter than standard 'boxes and doesn't use the engine adaptor sandwich plate. In conjunction with a Sprint axle, a prop from an auto' Sprint is about the right length. I had a custom made prop from Dave Mac Props in Coventry, but it cost me more than £250.

The Sprint 'box can be mated to 1850 engine, but as the 1850 sits at a slightly different angle the gearstick will be offset in the car toward the driver's leg.

Reasons to use TR7 Gearbox:


• It fits

Reasons not to use TR7 Gearbox:


• Its heavier
• Its more expensive
• Its less robust and costs more to repair when wrong
• You can't tow a car fitted with one due to oil pump mechanism
• You need a different propshaft
• Overdrive on 3 & 4 is far more useful than a long legged fifth gear
• You need to use TR7 clutch
• You preferably need to use TR7 starter
• You need to hack great chunks out of the bell housing casting to get it to fit past the steering rack

A very worthwhile modification, I have a Sprint gearbox fitted in my Green 1850 Dolly and it certainly makes hiway cruising easier & more enjoyable. Better fuel economy too!
You need the Sprint gearbox "adaptor plate", Sprint starter motor & sprint gearbox mount. As mentioned the angle of the box/gearstick is not quite right however all I did was cut a larger hole for the gear lever to protrude through the removeable tunel and its fine. Albeit the gearlever does lean a bit more than normal (away from the driver) but not a major issue. Then when I get the Sprint motor fitted I can just fit another gearbox tunnel.
You will only need the Sprint subframe if fitting the Sprint motor again due to the angle.
As mentioned Sprint diff is a straight swap but you will need a different prop shaft. I rumaged through my mechanics pile of tail shafts to find one that fitted so I'm not sure what it's off ,sorry. The only other thing that caused me a minor problem was the exhaust , where it ran across the rear of the 1850 diff. Once the larger Sprint diff was fitted the rear of the diff fouled the exhaust slightly. Just bent it out of the way a bit and sorted (does not look the best though!). The lack of clearance made it difficult to fit up the Sprint diff past the exhaust but I was doing this on my own so if you have someone to assist things should go smoother.
Even though my White Dolly has a six speed box I still find flicking the overdrive switch in my standard green Dolly a real buzz!!
Hope this is of some help?
Baz.

By "Adaptor plate" Do you mean the plate the box mounts too on the back of the engine? I thought that was the same between 1850 and Sprint... As do ANG Triumph.
Is it not possible to tilt the box using that back plate? Either adjust the holes, or make up another one with the holes in different places? Might be less of a faff then playing around with Engine mounts etc.

Can't remember what it looks like under there as I've only really looked at it twice.
That said though, I'm sure you guys that have done it would have thought of that first.
I'll shush.

There's an aluminium casting that fits between the sprint engine and gearbox, this tilts the box back over to counter the 5 degree tilt in the subframe. It also means the sprint box has a longer input shaft than the tr/2000.

Does make you wonder whether you could just fit a tr6 or 2000 saloon box to the 1850, it'd be the right way up then, though you would have to do something about the gearbox mount as the sprint one wouldn't line up any more and the prop would need to be ~1.5" longer.

Thanks Zombeh, I didn't know that.

TR7's come in 2 flavours...the 4 speed earlier coupes use the single rail box which is the same as a dolly one bar that it doesnt have overdrive and bizarelly has
different reverse....same ratio as ohv cars like spits etc. Weird. The forward gears are the same as dolly ones. Also the axle on these cars has the same dolly diff unit and 3.63 ratio but longer tubes and half shafts with bigger brakes. Ive nicked the diff unit and fitted it to an 1850 diff...its the same. Obvioulsy the 7 version also has a different bell housing and longer input shaft. No use on dolomites....you need a dolly input shaft and bell housing.

But the single rail box or earlier 3 rail is a bit marginal on the TR7 engine. So later 7's use the LT77 (rover SD1) box with 5 speeds and a different diff altogether. I've never had one in so don't know much about it. I do have a TR7 LT77 and have often wondered about using it, but it looks quite involved with drilling bosses, adapting sprint cross shafts or changing to a cable actuated clutch. Its all been done though but as I don't need to I havent bothered.

Next time I do a dolly 7 though I will use a sprint diff, prop shaft, box and adaptor plate. I reckon this would make a nice car of it. the sprint box does have its issues, but these are mostly clutch cross shaft or wedgelock pin related. Minty lamb's website tells you how to mod the box with a sierra internal slabe cylinder. Not sure about that myself but apparently it works well on TR's...

The sprint driveline also mounts the box lower, so the rear mounting gets an easier life without the box yanking it about so much.

Jonners

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Note from Admin: sadly Jon passed away in February 2018 but his humour and wealth of knowledge will be fondly remembered by all. RIP Jonners.

1. Yes you could, but the bell housing bolt holes are consistent so it wouldn't be the right way up
2. I've seen propshafts with solid metal spacers inserted between flanges with longer bolts through the lot
3. The gear stick would foul the parcel shelf/radio in neutral, first and third.

Thanks for all the info guys. I could get a cheap tr7 locally but I think I'll try and find a knackered sprint and swap the bits. Aberdeensprinter has an old dog up in caithness I'll try and pry from him for a bag of pork scratchings and a bottle of magners.
cheers fellas

There is a Sprint in 'borders' on ebay at the moment. looks too good to be a donor though...

Am watching said sprint at the moment. It's only an hour from me but I like donor cars to be free or even cheaper. Like you said, a bit too good to be ripped apart.

Oi Scotchy......Where's my pork scratchings and Magners!!!.....

You should fix it up....go on....you know you want to...










Dove Group Motors....

I tried to post them but the bottle broke when I forced the package into the pillar box.
I'll settle up in june, will a bottle of panache and a croque monsuir avec frites do?

Back to the subject. with regards the future engine swap, If I stick with tre spint box/axle, what sort of power limitations do the standard box/o-drive & diff have? I'm only looking at 150-180bhp max. both will be getting rebuilt before being used.