Automatic tansmissions - Sprint v 1850

[gmsclassics]

Can anyone tell me what the technical differences are between the Sprint and 1850 automatic gearboxes? They seem to have different part numbers on Rimmers website, but both use the same drive plate and torque converter. However the Haynes manual doesn't appear to differentiate between them.

I am rebuilding a Sprint and thought about making this one an auto (I already have a manual overdrive one). However I cannot find a Sprint auto box in NZ, yet there are plenty of 1850s around.

Does anything else fit? As far as I can see only the TR7, but I can't ever recall seeing an auto one. Again the big Triumph saloons have a different part number unfortunately as these are two a penny.

Geoff

[JPB]

Internet automatic transmission guru Harvey is the man to tell you the technical ins and outs of this but I suspect that there must be internal differences between the BW65s fitted to Dolomites, Sprints and TR7s.
Fortunately, he generally finds posts where his name is mentioned so Harvey, if you're out there......



(Later TR7s use a BW66 by the way, and I've seen one with a BW45 (4 speed) which I know wasn't a factory job).

[1300dolly]

If they are both BW65s then surely there is no difference in the box ifself only the bell housing.

[harvey]

Fortunately, he generally finds posts where his name is mentioned so Harvey, if you're out there......

......And as if by magic........

I have listings that show them as different boxes, I'd assume that the bellhousings and tailshafts and housings would be the same as the engine uses basicly the same block, and the box is mounted in the same position in the shell. There can be differences in the internals, the number of friction plates can vary according to the application, the Sprint would have the maximum I would think, the 1850 less possibly. Difficult to know without a look in the book to see if it gives the number of plates, but if it was rebuilt it could always be changed to accept the maximum number of plates. Biggest problem could be the band operating servos, as they vary in size between models, and as they run directly in the main casing then if you need to change that, you would need to change the casing itself. I'll see if I can find the sizes for those for both boxes to see if they are the same or different.

[Edit] Looks like Jag/Rover/BMW have the larger servos, Austin/Morris/Triumph are listed together with different servo seals, so unless the Sprint is an oddball Triumph box it should use the same casing as the 1850.

There are choices of 4 or 5 plate clutch packs so I'll try to find whether the 1850 and Sprint use different ones.The Dolomite factory WM doesn't cover the Sprint at all, and doesn't list the number of plates either. Looking at the illustrations (which aren't necessarily accurate) it shows 4 friction plates in the front clutch, and 3 in the rear. Whether this is correct or not, I would guess that the Sprint uses the maximum 5 in each, and that would account for some of the differences. Also the Stag and PI Triumphs had different valves in the valve block to delay the upshifts to make the box feel more "sporty" and it may well be that the Sprint has these as well.

As a guess I would say that you could fit an 1850 box, even if it isn't up to the same standard as the Sprint one, it just won't last as long if that's the case, or dismantle it first and uprate it.

[Toledo Man]

Every home needs a Harvey...

Getting back on topic, I've checked my parts catalogue and the part numbers for the 1850 & Sprint autoboxes are different but the main casing is exactly the same.

[gmsclassics]

Many thanks everyone and especially Harvey.

I now know a lot more about auto boxes.

Geoff