The Triumph Dolomite Club - Discussion Forum

I’ve just bought a ‘74 Toledo fitted with a TR7 engine and 3 rail 1850 overdrive gearbox. It’s got a couple issues I was aware when I bought it that I’m trying to sort out. It’s a known car on this forum - GLF998N.

Firstly, the gearbox is rough going into second gear and noisy in all gears except 4th. I took a video today with the back off the ground, unfortunately you can’t hear very clearly, but here it is: I’ve also taken a pic of the clutch master and slave.

https://youtube.com/shorts/mn1a8e0hhgM



Firstly - given the sounds the gearbox is making is it worth investigating clutch issues? I’ve not tried bleeding it yet. I did remove the carpet allowing the clutch to hit the floor which I think slightly improved things. The slave is installed with the bleed nipple up, is that right for the 1850 box? Can anybody tell if that’s a Toledo or 1850 master?

If the gearbox is definitely the issue, is ok to keep driving it assuming it’ll need rebuilt anyway or should I park it up to not make matters worse - is a thousand miles while I figure out a replacement going to make much difference? It’s perfectly drivable but a little noisy and requires gentle treatment.

The other issue is the cooling system. It’s recently been fitted with a mk3 fiesta diesel radiator, new thermostat and a fan on a switch. It was running a bit hot sometimes - never going past 3/4 but occasionally past 5/8ths. I bled the system today and took it for a run, it’s seems to be running cooler but after getting stuck in traffic it crept up to about 5/8ths.

I bought a laser thermometer and checked it against the OBD readings on my freelander - getting the same reading off the engine and radiator as OBD +- 3 degrees. On the triumph I was getting 85-95 off the engine at half way on the temp gauge and 95-100 at 5/8ths. Is that hot enough to worry about? When driving on the open road it drops below half.

The thermostat housing tended to give me higher temperatures than the engine. When warmed up the expansion tank was giving me similar to the engine, but the radiator was at about 65, with the fan on. Heater worked fine before and after the bleed.

What I ended up doing to bleed it was unclip the return pipe from the expansion tank, block the return hole in the expansion tank and, hold the pipe above the engine with a funnel attached and burp the top pipe - I kept going until I didn’t get any bubbles, redlining the funnel as needed. However I’m now realising as I write this that for reasons I’m sure made sense to me at the time I didn’t run the engine while I did this.

Do those temps sound ok - I’m wondering if having a Toledo temp gauge hooked up to an 1850 sender is causing it to show higher temps or if it’s running too hot.

Should I rebleed it using a better method? Is the radiator perhaps too small? Blockage or duff water pump? One thing I’m definitely going to do is fit a thermostat controlled fan at some point.

Thanks, sorry for the multiple and perhaps silly questions

Gearbox layshaft will 99% be the culprit. Or rather the layshaft pin and/or bearings.
Time for a refresh. And the issue is VERY common, it doesn't get better as the wear rate accelerates. Best bet if you need to drive the car around is to be gentle on te accelerator in ears 1-3, get into 4th ASAP.

I agree with Clive. If you have a noisy box in all gears except fourth, that points to the layshaft bearings.

Great, thanks guys! I’ll start looking to rebuild or replace and give it an easy life till then.

If I found an 1850 single rail or Sprint gearbox what would I need to change? Master, slave and prop? Are the mounts the same? Would I need a sprint axle? Any other gearboxes worth considering? I’d want to keep the overdrive or go 5 speed, but I figure a 5 speed swap would be more hassle/cost than the other options.

For a Sprint box you need to change lots, probably not worth considering.

An 1850 single rail box will need the correct prop, gear lever and tunnel housing and the overdrive adaptor section must match the gearbox (see Mad mart's 1850/Sprint gearbox thread on this page.) Mounting is the same, just use the next set of holes in the floor. I'm pretty sure the expensive O/D unit is interchangeable between single and 3 rail boxes.

Last I looked, there was a single rail O/D box without the O'D but otherwise complete on the official TDC facebook page.
I have a spare single rail 1850 tunnel in fair condition. Props can be specialist shortened easily and not too expensively, I had 75mm removed from the front of my Sprint prop for only £50.

Steve

Carledo wrote: ↑Wed Sep 14, 2022 11:01 pm For a Sprint box you need to change lots, probably not worth considering.

An 1850 single rail box will need the correct prop, gear lever and tunnel housing and the overdrive adaptor section must match the gearbox (see Mad mart's 1850/Sprint gearbox thread on this page.) Mounting is the same, just use the next set of holes in the floor. I'm pretty sure the expensive O/D unit is interchangeable between single and 3 rail boxes.

Last I looked, there was a single rail O/D box without the O'D but otherwise complete on the official TDC facebook page.
I have a spare single rail 1850 tunnel in fair condition. Props can be specialist shortened easily and not too expensively, I had 75mm removed from the front of my Sprint prop for only £50.

Steve

Apart from a clutch plate and adding an adapter plate, what else would need changing in addition to your list there to fit a Sprint ’box?

I have spare Sprint ‘boxes and adapter plates in Stourbridge; far more robust than 1850 units….

Indeed the 1850 boxes are all a bit fragile. But a 3 rail j type will always have value even if needing a rebuild, so will offset costs.
I used a sprint n=box on my tr7 powered toldeo, much tougher. I also used a sprint axle and prop.

The sprint axle has a long "nose" so the sprint prop will not fit your axle. You would need to get yours shotened, but that is the route I would go down if you expect to give the car any grief.

Of course, getting yours fixed is the other option. Not sure how much a professional refresh would be.

Good choice of car !
Just a couple of observations:
Gearbox. Since you have just got the car, I'd change the gearbox oil and clean the O/D magnetic filter. ( 6 bolts ). Refill with a good quality 85/90 GL4 oil. I don't think that it will make much difference to the noise / quality of change but it is a peace of mind thing.
Clutch : Yes, I'd bleed the clutch. The bleed nipple on the slave cylinder is correct ( upwards ) . On my 1850 I bleed the clutch every year as the biting point gets lower & lower. I've never found out why. I never bleed the MGB clutch by comparison.
I'm not sure which clutch fork is used in your TR7 / 3 rail system but if it is the same as the 1850 I'd inspect it for cracks around the pivot point. This causes the biting point to suddenly drop to the floor.
HTH,
Tony.

Thanks again everyone. Definitely leaning towards replacing with a stronger unit as opposed to rebuilding my current one, and ideally a sprint one.

If I’m not changing the gearbox soon I’ll change the oil and bleed the clutch and check the fork. Is it relatively straight forward with the gearbox tunnel out?

Would a sprint gearbox fit with the existing prop and axle, or existing axle and a modified prop?

Will a sprint gearbox and prop work or does the gearbox adaptor plate mean it will be too long and even with a sprint axle I’ll need a modified prop if it switch to a sprint axle?

Does the will the current overdrive adaptor plate for the overdrive fit the sprint box? Mad Mart’s thread makes it sound like I only need a new adaptor for the single rail 1850?

Here is my parts list so far so I can start pricing up a sprint box:
Sprint Gearbox
Sprint gearbox adaptor plate
Sprint gear lever
Sprint Clutch
Sprint gearbox mount
Sprint axle?
Sprint prop or modified prop?
Sprint flywheel? (No)
Edit: Sprint starter? (No)


Does that sound right?

xvivalve wrote: ↑Thu Sep 15, 2022 3:25 am
Apart from a clutch plate and adding an adapter plate, what else would need changing in addition to your list there to fit a Sprint ’box?

Clutch slave and pipework, engine backplate, possible flywheel, starter motor. There's also the consideration that this car was a Toledo, it may still have the subframe from the OHV engine with the long rear extension. It's quick and easy to cut the OHV mounts off and the 1850 mounts are there already, as they are on a Sprint frame. This is fine for both single and 3 rail 1850 boxes but NOT for the Sprint box. The final nail in the coffin for me, is that the 1850 (/TR7) and Sprint engines sit at a slightly different angle, marrying an 1850/Tr7 block on 1850 mounts and subframe to a Sprint box means the box is a few degrees out of kilter. It's not enough to make the job unfeasible but the couple I've experienced just felt a bit odd to drive.

A Sprint box IS a tougher box, no doubt about that. But the Sprint box comes with it's own peculiar problems in terms of cross shaft woes and clutch bleeding, the laygear bearings still aren't brilliant and Sprint tunnels are getting so hard to find the club's making GRP ones.

The single rail 1850 box is the last development of that venerable series (which goes back to the Standard 8 and 10) and by far the best. It took care (FINALLY!) of the boxes biggest drawback, that tiny bearing twixt first and third motion shafts and the little mainshaft circlip. The 3p part that took out far too many gearboxes! No, it's not the best, and certainly not capable of coping with high output motors, but it's not as bad as it's painted.

Steve

Nah, backplate, flywheel and starter are all cross compatible. Slave cylinder usually still bolted to the side of the ‘box.

Cheers both, still torn between 1850 single and sprint. I’ll probably go with whatever I can find the requisite bits for. I’ll get under the car and see what subframe I have.

Edit: I've had a look and I think it is and 1850 subframe.