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TR6 'A Type' overdrive not working


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Hi, Guys & Gals.


A quick question, if I may.  I have a 1971 TR6 with factory fitted 'A Type' overdrive.  Suddenly, the o/d has stopped working.


The switch seems OK - and is relatively new.  The previous (possibly original) one failed a couple of years back.  It became "floppy" to the touch.  I replaced it, and all was well again.


Diagnosis so far.  


Putting the ignition on, with the car in fourth, and flicking the switch in/out, there is a distinct "click" - but I'm pretty sure this is  coming from the relay (nearside under the bonnet, near the bulkhead).


Testing this relay, I get as near as makes no difference to 12v from port C2 (central, with yellow/purple wire) when the o/d is switched on - and zero when it's off.


I suspect a failed (or disconnected) solenoid .


Before I make too big a job of it, how do I access the solenoid, please?  From inside the car?


Grateful for any advice.



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the energising solenoid is mounted low down on the N/s of the unit ,, on the O/S is a protruding shaft witha setting lever attached, there is a  3/16" hole in the lever which when engaged should align with a hole in the oute case.


you may  just  see this from under if not its tunnel off.


first check   does it move when the switch is operated 

if it moves but wont align remove the cover in front of the solenoid and adjust the lever throw pushrod. ( there are some  dimensional settings for the pushrod and solenoid piston end float  and its end stop settings )


if it doesnt move expect a electrical problem in the feed or a duff solenoid


as with Dtypes there is a switch in the end of the  A type solenoid which cuts a pull in coil current of15 amps down to a holding current of 1 amp

some of these switches can be access cleaned etc some are fully sealed and you cant do much with them.


thats a start 



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The majority of overdrive problems are electrical. The other thing to check is the oil level in the gearbox. 

If both of these are ok then there is a more serious prob.

The US Buckeye Triumph website has some great advice on more serious overdrive work. If you decide against this then I can recommend Overdrive Repair Services just outside Sheffield. Again they have a good website.


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yes the  OD oil level is all integrated with the gearbox  so only one level filler ...the one for the gearbox


the overdrive is engaged by oil pumped at pressure so any low  oil  level in the gearbox will adversely affect the overdrive operation 


once the level is below the pump pick up .


and the inhibitor switch can get full of green corrosion ,thye can with care be stripped  cleaned and re crimped together

most are a lucas SA141 type which is a simple bell push design .



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  • 2 weeks later...

Many Thanks, Pete and David.


Sorry for the delay in responding, I'm afraid I got sidetracked with other issues.  


Thanks for all the advice.  The fault is definitely with the o/d solenoid, and after "doing battle" with some overly tight bolts, I'm delighted to let you know that I've got the tunnel off, accessed and removed the solenoid, and am now awaiting delivery of a replacement (due tomorrow, Tuesday).  Only snag is I'm having "hell's delight" in trying to get the oil filler plug out (and yes, my fault - haven't done that regularly enough over the years!).  Hopefully I'll get there in the end, though - should be a darned sight easier to check / refill [as necessary) with oil from the top now the tunnel's out, than from below.


Cheers,   Graham.

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