tr7 gearbox conversion

[triumphjim]

hi, have being looking to uprate my 1850 engine, but before i do i need to change the running gear as it is so weak on the 1850, so a sprint back axle, got a sprint box already but do not like overdrives for constant usage, would like a 5 speed as i am planning to use it as an everyday car, had a look around and am unsure why anybody has not used the tr7 gearbox? uses same clutch parts 1850 or sprint, about right size shape,mounting points are close and early tr7 prop is overdrive spitfire type.. any reason why i should not use this gearbox? has anyone already done this to give me any pitfulls? way cheaper to do than type9 or mt75 by the look of it. any info greatfully recieved. jim

[Oli_88]

Alun has done it, from this topic.
viewtopic.php?f=4&t=15930&p=157600&hilit=+LT77#p157600

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

[sprint95m]

What age is your 1850?

Early engines have six bolts for the flywheel so will not accept the TR7 flywheel.

[triumphjim]

hi,mine is a late 76 dolly, i thought that the tr7 box would be more robust as it is taking the 2.0l engine torque. got a sprint engine aswell, but really wanted to keep the 1850 in and just push it up a bit on the power.thought the blocks/crank were the same on sprint,tr7,1850 . shows you just how little i know about these cars. suppose i will have to just put the sprint box,prop and axle in for better criuseing ability and strengh, if i port/polish and skim head to 9.5 and have a decent four branch off the stag/tr7 type and may need sprint carbs? hope to get 105-110 bhp, think this would eat the axle and box of a 1850. do not know many people who bother to tune the std 1850, i think this is a shame as it is still a good smooth engine. regards jim

[Carledo]

The TR7 box (LT77) also backs up the rover V8 in several apps, SD1, Tr8, range rover, LDV400 Ambulances etc ad nauseam. Its not that weak! There are as above a few problems with fitting it to a dolly but its not the PITA that a Type 9 is. If you do this I'll swap my sprint auto prop for your manual one, mine needs a new centre bearing though! Steve

[JPB]

If you want to run a 4 branch manifold, you'll need a TR7 to put the engine in . The late Bobby Brown from Prestwick (by Ayr airport) made one or two for 8V slants in Dolomites and a proper work of art they were too but, assuming you can't find one of his, you'll be stuck with the hockey stick effort.

[Oli_88]

Is it not possible to fit a tubular manifold, if you scallop the left had turret?


Admittedly an extreme solution...

Also, to my eye, the stock TR7 manifold looks to be much better than the 1850 one, I'm quite convinced that with a custom downpipe it could still join to the stock exhaust system...

[Mad Mart]

It has been done by a few...



Taken at Cosford TDCIR a few years back.

[Carledo]

It has been done by a few...



Taken at Cosford TDCIR a few years back.

Jeez Mart , that is a real banana bunch, I dread to think what the underbonnet temperatures were like! Steve

[Powderfinger]

Underbonnet temps would be fine with this http://www.zircotec.com/ Run it on a full race Riley and you can touch it after 45 minutes on the track as soon as it comes in. Just remember that the exhaust gets hotter further down the line instead tho.

[triumphjim]

hi, will have a look at the tr7 manifold solution , yes would definitely give better exhaust extraction. if anyone has a picture of the bobby brown manifold i may be able to get a copy made.was going to put rimmers lower and uprated springs on but they list them as 175lbs rate and i have been told my dollys got 185lbs aprox as std, so the uprated ones are softer than the orginals.will have to buy one out of one of the motorsport places and specify my own size spring and rate,i suppose. has anyone had any experience with the rimmer ones to let me know if they work well with better handling but still give a reasonable ride. will post pictures of the exhaust when i managed to figure one out that fits ok. regards jim

[harvey]

Reasons not to use TR7 Gearbox:



• You can't tow a car fitted with one due to oil pump mechanism

That's not the case, it's not like an auto just because it's got an oil pump in it, and believe me I would have found out by now because over a period of about fifteen years I towed hundreds of them without any problems whatsover from doing so.

[Oli_88]

Well they got that a bit wrong, they're 137lb stock. It's been said before that 200lb is about the max for a road car, personally, I'd experiment and see what works for you.

[triumphjim]

hi,thx rimmer ones sound about right then, do not want to uprate to much as i will be using as my daily drive. has any one tried seeing what a stag sports manifold fit is like on a 1850, was looking at the rimmer sight and the tubular manifold for the stag is built very narrow so should clear the turret and is very short to allow your own lead away of down pipe. it is facing the wrong way but still might have the clearance or aleast a start point if the basic clearance is there and copy it toface the other way. regards jim

[triumphjim]

hi,was looking at the tr7 box as i thought it would be a reasonable swop,thought i could use the clutch plate and housing, one off a 1850 and other off sprint as they are same part numbers that fit the early tr7 box and use the early tr7 prop flange onto the dolly prop, did not know the bell housing was so much bigger to foul the steering! that one i cannot easily get around... as my daily drive is 50 mile round trip, all at reasonable speed, no crawling threw towns as i live in norfolk, i thought the five speed would be best option for reliable,economical runs. though i suppose a sprint axle would reduce the revs to a reasonable level. regards jim