The Triumph Dolomite Club - Discussion Forum

Is the engine back plate on the automatic the same as what is installed on a manual car? Does the TR7 flywheel need machining in the rear to fit?

It is many years since I had a Sprint engine and a TR7 engine sitting side by side in my yard and it was before I contracted narcolepsy which has affected my memory for the detail of such things, but I recall the fundamental difference is the TR back plate is fixed with countersunk screws instead of bolts which allows the flywheel to sit closer to the back plate. If you want to use a TR flywheel then yes, I believe it needs machining to prevent it contacting the bolt heads on a Dolomite engine. Because the ring gear will then he in a slightly different place, you may also have starter motor issues.

Whilst the back plate on an auto' is, I believe, the same as a manual, if intending to use a TR flywheel, I would recommend also sourcing the TR backplate and fixings and the starter motor as well.

xvivalve wrote: ↑Sun Jan 14, 2018 7:49 am It is many years since I had a Sprint engine and a TR7 engine sitting side by side in my yard and it was before I contracted narcolepsy which has affected my memory for the detail of such things, but I recall the fundamental difference is the TR back plate is fixed with countersunk screws instead of bolts which allows the flywheel to sit closer to the back plate. If you want to use a TR flywheel then yes, I believe it needs machining to prevent it contacting the bolt heads on a Dolomite engine. Because the ring gear will then he in a slightly different place, you may also have starter motor issues.

Whilst the back plate on an auto' is, I believe, the same as a manual, if intending to use a TR flywheel, I would recommend also sourcing the TR backplate and fixings and the starter motor as well.

The ring gear on the Dolly Sprint and the TR7 appear to be in the same position in my photo here, it just the extra material on the rear of the TR7 flywheel that makes it approx 2kg heavier.

I put an engine from a manual into my auto last year and they are the same.

The clearance with the flywheel is very tight so I would think that you need the countersunk bolts.

I must admit that, being an auto nut, I am sorry to see another one go.

AlanH wrote: ↑Tue Jan 16, 2018 5:14 pm I must admit that, being an auto nut, I am sorry to see another one go.

Same here, I really enjoy driving my Sprint and 1850 autos, both have rebuild boxes and they run sweetly and the 1st to 2nd change is almost un-noticeable.

I am reluctant to sell my 1850 auto for fear of it being converted but each to their own.

You didn't perchance find out if there were any differences between the 1850 and Sprint auto boxes when you rebuilt them did you? Types 11 and 17 if my memory is correct. Reason I ask is that when I converted one of my Sprints from manual to auto I could only find an 1850 transmission and all I've changed is adding a transmission cooler.

If your 1st to 2nd change is almost un-noticeable, then mine needs a rebuild too!

Geoff

gmsclassics wrote: ↑Wed Jan 17, 2018 9:10 am You didn't perchance find out if there were any differences between the 1850 and Sprint auto boxes when you rebuilt them did you? Types 11 and 17 if my memory is correct. Reason I ask is that when I converted one of my Sprints from manual to auto I could only find an 1850 transmission and all I've changed is adding a transmission cooler.

If your 1st to 2nd change is almost un-noticeable, then mine needs a rebuild too!

Geoff

I have a few spare auto boxes and all the valve chest/box have the same number of 6005. The number of clutch plates was the same in both which I think is four but there is a thick spacer in the clutch assembly. I removed that and fitted an extra clutch plate and disc, the total thickness is the same to within 0.015' . the speedo drive is different; green for the 1850 and red for the sprint if I remember correctly.

some of the boxes have different brake bands, one of my boxes has two bands the same and the sprint box and two different styles.

I think to improve the smooth change up, it may require the bands adjusting, but when I took the pistons out of the servos I did find them stiff, hard rubber seals and full of gunge, one servo can be changed with the gearbox in the car but the other one is more difficult due to space restrictions.

Malcolm