Into overdrive!
Matt works methodically to restore TR’S cruising capability
After trying my hand at upholstering interior trim last time (PC, December 2021), I was then able to move onto some more greasy jobs. When the TR was restored ahead of a return to the road in 2019, I replaced the original A-type four-speed manual gearbox with a later J-type manual overdrive gearbox from a Triumph 2500 saloon. This required changing the gearbox output flange and using a different setup for the gearbox to chassis mount, but otherwise the ’box has worked well up to now. The only niggle related to the overdrive, which was always slow to engage when cold, but otherwise worked perfectly when required.
However, over the past year or so, it had become much more hit and miss in operation, until it finally stopped working completely. I went for the easy option first and checked the gearbox oil level (the overdrive shares its oil with the ’box) – nope, plenty of foul-smelling EP 80w90 in there. This led me to engage the services of my dad, Keith, and his trusty multimeter. I’m lucky in that, after a successful career as an electrical engineer, I can rely on him when it comes to such electrical issues, as I’m no expert myself.
Dad went to work and soon, the verdict was in – all of the wiring to the overdrive unit was intact and the solenoid itself was receiving 12v when the overdrive switch was operated. This proved what I thought might be the case originally and confirmed the overdrive solenoid was the issue.
In with the new
After searching around for a replacement, Revington TR in Somerset was able to provide a new solenoid. Once that had arrived, it was a case of first removing the central ‘H-frame’ that sits below the dashboard and on top of the gearbox tunnel. Thankfully the TR has an aftermarket two-part tunnel, so only the rear section needed to be removed to allow access to the overdrive and solenoid. Once exposed, it became clear that the earth lead from chassis was very poorly connected to the solenoid, while having been covered in a lump of solder at sometime in the distant past. Could this have contributed to the symptoms I’d been experiencing? Quite possibly, but the new unit went in all the same.
Having done this job previously on his own TR, dad already had a suitably trimmed down spanner that could fit on
the skinny nut in between the solenoid and the overdrive body. With the wiring checked and cleaned up, the new unit was fitted and dry tested, with the solenoid producing a satisfying clunk when third or fourth gear was selected, ignition on and overdrive switch engaged. A quick road test confirmed all was well. Job done.
The need for speed(o)
While the gearbox tunnel was removed, I was also able to fix another issue. The TR’S speedo had also stopped working and I suspected the speedo angle drive on the side of the gearbox, which is where the speedo cable connects.
I’d bought a replacement from TRGB in case the angle drive was at fault. Which it was… kind of. The two parts of the angle drive had parted company, with one part still attached to the gearbox and the other one dangling on the end of the speedo cable. With the two parts firmly screwed back together, the speedo started working again. I was able to return the spare angle drive I’d bought, and hopefully this issue is now cured, but I’ll keep an eye on it.
With the big ticket tasks successfully completed, I finished up with a bit of automotive housekeeping and general good practice.
The TR’S engine has now covered c.2000 miles since it was rebuilt for the second time and, having changed the oil and filter after 500 miles, I reckoned it was about time to repeat the trick. With the car on the two-post ramp in the PC workshop, this was simplicity personified and a NOS Unipart GFE 227 oil filter was fitted, before the sump was filled with fresh 20w50.
While the underside of the car was readily accessible, I also drained and refilled the gearbox and overdrive with fresh 80w90. The oil had been in there since the car went on the road in Spring 2019 and was clearly due for retirement, so it was a task well worth doing. I also topped up the differential and pumped some grease into the propshaft and driveshaft UJS for good measure.
The TR’S running well and I’m really enjoying driving it, so we’ll hopefully be getting out and about over winter if possible. Fingers crossed!
‘Our electrical investigations proved solenoid was at fault’