ctc77965o Posted December 29, 2011 Report Share Posted December 29, 2011 Hi All, My 4A's overdrive was an exchange unit fitted in ~'94 and did ~40K miles up until '99 without incident. I then dry-stored the car until 2007/8 and have been slowly getting it back on the road (mostly body/chassis restoration/replacement). Now it runs fine but the overdrive distinctly doesnt. Electricals all OK, gearbox topped up with oil, but no overdrive.... it's not jammed 'ON' as the car reverses cleanly. With the car on a lift I have run the car in top gear to try manual actuation of the lever/solenoid, no luck there either, however with the engine just stopped I can actuate the lever and hear a sharp thwack inside the overdrive for the first two actuations (i guess residual pressure drops away after that). So, I'm thinking that the cone clutch is seized on the annulus...not sure I'm using the right words...I'm thinking the overdrive is jammed in the 'normal' condition rather than in the 'overdrive' condition. It seems I have at least some oil pressure and that the operating lever is doing it's job, so it appears the hydraulics are working but the thing is mechanically jammed.... What do you think?? I guess next test is to measure the pressure. Do you think it might free-up once fully warmed-up with the overdrive actuated? [i'm only going round the block as the car's not registered for road use yet] Any other de-seizing ideas?? Quote Link to post Share on other sites
johnny250 Posted December 29, 2011 Report Share Posted December 29, 2011 I believe that it's possible to whack the exposed portion of brake ring with a copper/hide hammer to free it off if stuck. john Quote Link to post Share on other sites
BrianC Posted December 29, 2011 Report Share Posted December 29, 2011 On a couple of occasions, shortly after having my A-type overdrive restored it failed to engage on cold mornings. The first time, I tried repeatedly on each journey and came to the conclusion I would have to return it to the restorers, but fortunately on a longer journey it decided to start working. I assume this was simply because the whole assembly and the oil had thoroughly warmed up. The next time it happened I just took it out for a long run and again it eventually started working. Since then, I have done another 14000+ miles with no repeat. So, if all electrics and oil levels are OK, then TRy a longer trip (at least 10-20 miles) before getting too technical. Quote Link to post Share on other sites
ctc77965o Posted December 29, 2011 Author Report Share Posted December 29, 2011 Hi John & Brian, Thanks for the inputs... I tried whacking the brake ring to no effect, but I think that only works if it's stuck in overdrive...I'm thinking my issue is the same but on the other side of the cone clutch... Anyway, i will put it out of my mind and get some miles on it to see if it sorts itself out...certainly a lot less effort than getting surgical at this time.... Dave So, if all electrics and oil levels are OK, then TRy a longer trip (at least 10-20 miles) before getting too technical. Quote Link to post Share on other sites
Tr4Tony Posted December 30, 2011 Report Share Posted December 30, 2011 Dave Sounds like the clutch rings are stuck in the overdrive unit .... this happens, just like a flywheel clutch stickng to the flywheel if the car is not used. Generally, if you muller it in any way you end up damaging the clutch material so I'd be careful when walloping anything with hammers or pushing probes into the housing etc. as you will ether crack the casing, break the oil seal or damage the clutch rings themselves. The best cure is to run the gearbox out of overdrive (if stuck in and vice versa if out) and eventually it will free up and react appropriately - usually its an indication of a good thick lining, so treat it carefully and it will come into its own in good time. Regards Tony Quote Link to post Share on other sites
ctc77965o Posted December 31, 2011 Author Report Share Posted December 31, 2011 All, Took the wife for an inaugural spin today (I'm talking about the Triumph here), and after 15 mins or so my 3 extra gears appeared! As suggested, driving with the overdrive selected ....possibly with the additional weight of wife :-o .... caused the thing to break free and resume normal service...! Happy New Year! Dave The best cure is to run the gearbox out of overdrive (if stuck in and vice versa if out) and eventually it will free up and react appropriately - usually its an indication of a good thick lining, so treat it carefully and it will come into its own in good time. Quote Link to post Share on other sites
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