Overdrive Engagement

[philt]

I have a K reg Feb '71 Stag, so mark 1, but somewhere along the line it has acquired a J type overdrive which is more a mk2 fitting.

In 15+ years ownership apart from sometimes a sluggish take up - which was resolved by topping up the gear box oil level - its never caused a problem until now.

That problem being that after driving for say 20 miles, some of which will be in overdrive, it will fall out, try and engage half a second later and repeat many times in the next few seconds before one gives up, switches it out of overdrive and marks it down as a job that needs doing.
The solenoid has been changed as that 'fix' as has the oil seal and the wiring up through the gear stick is allegedly OK.

Last evening it didn't even wait until 20 miles, as in first mile or so we had the overdrive 'hokey cokey' - its in its out.... repeat until patience decides that it aint gonna work and you switch it out.

Any thoughts anybody?

PS - I have a sleepy alternator as well. That only starts to charge after 10 minutes of driving, but it always does wake up. Is it all related?

[StagJonno]

From the intermittency, I'd be first suspecting a broken/ poor connection in the circuit, or the switch has dodgy contacts. Also check the fuse & clips, as I've heard that several owners experience problems with fuse contacts.

Re alternator - is it really time related, or is it linked to revs? On mine, the alternator generally needed for the engine to go up to 2,000 - 2,500 rpm before starting to charge (ie the IGN light going out). After that, charging appears to be normal, according to the dash Voltmeter. Apparently, according to the PO who had just fitted the higher rated alternator shortly before I bought it, the previous alternator behaved similarly. I have noticed recently that this issue is not occurring very often. Can't explain this, but a mechanic friend advises that this is not uncommon on classics.

Mine's a '76 Mk2, with the regulator built in.

Jonno

[DJT]

Sounds very much like the wires that run inside the gear lever to the switch. They often fail at the base of the lever and cause this intermittent problem as the broken ends touch/part.

You can get new wires here, complete with the correct terminals: http://www.angclassiccarparts.co.uk/...m-triumph-stag

[philt]

Thanks for feedback. I'll go and buy some wires and see if that does the trick.

Re the alternator - its a recon 11AC one from Rimmers that was fitted in the spring after the previous one died. After first fitting it the normal scenario of switch on, fire up engine and boot the revs up for a second or so brought it into life and the red ignition light would go out and the volts gauge go up to its usual 15V. That doesn't work any longer and even driving 5 miles or so with the revs up to normal open road speed of 50mph and revs at 2500rpm doesn't stir the thing so the red ignition light is on the volts at 12.5(ish); until - as I said - it eventually stirs and we are back to normal.

[stagmuffin]

Hi had the same turned out to be the o/d clutch eventualy consumed itself and spat out the shrapnel ! Do hope its just as simple as a wire but keep the wallet handy for the od rebuild

[TR5convalescent]

These can be an absolute sod as I know from my TR6 days...

Firstly check your wiring for continuity and resistance. I don't know what it's like on the Stag but a1973 TR6 I owned had an overdrive power feed which was actually thinner and had a lower capacity than the sidelight lead on my BMW Mini. That circuit draws around 8 amps. I replaced it with 20 amp cable.

Secondly make sure that the ENTIRE contact area in the switch is clean and not oxidised and check continuity over every square millimetre of conductive metal. I had a column switch which looked fine and gave good readings until I moved the meter probe around and discovered that about 2/3rds if the contact area was not conducting! I replaced the switch.

Thirdly,, if there is a relay (as well as the solenoid) make sure that it conducts constantly when engaged. Some of them 'flicker'.

Fourthly, with the engine off engage 3 direct, turn on the ignition and engage overdrive. Do you hear the distinctive 'clack' as the solenoid engages? Leave the ignition on for a few minutes and see if you can hear it engaging and disengaging. If you can, you have either a power feed problem or a duff solenoid. Be aware that some of the pattern solenoid are crap. Try people like T D Fitchett who might have NOS. it'll be about double the repro price but will probably last ten times as long.

Finally, check the tiny O rings on the solenoid. The second time my OD did what yours is doing I went through all,the above and finally found a microscopic nick in the O ring which I replaced at a cost of 30p. Problem solved!

Hope this helps. Good luck!

David.

[philt]

All
I've replaced the wire that goes from the switch on top the gear stick down through the shaft, and cleaned all contacts. Then done the check with ignition on and engine off and can hear the overdrive 'clack' as it goes in and out.
Sadly a road test reconfirms that the problem is still present.
The solenoid as well as the O rings was changed a few months ago when the garage was convinced that would solve the problem.
45 year old cars. Love em!
Phil

[StagJonno]

Next thing I'd do would be to run a bulb on long leads, connect across the solenoid and take the bulb into the car so you can observe it coming on and off with the solenoid and confirm if it's electrically related or mexhanical, inside the OD. The leads would need to be clipped (cable tied) to prevent them from snagging.

A possible problem with this arrangement is that when the solenoid is de-energised, there'll be voltage transient when the power from the solenoid is switched off which might cause the bulb to blow. This could be managed by appropriate use of a diode, or incorporating a relay in the test circuit. Happy to provide sketches if you want to follow this route.

Jonno