View Full Version : retired overdrive

09-25-2004, 06:41 PM
Dear all,
Last year I bought a TR-4 (1963) and although I had to do a lot of maintainance, we drove about 9000 miles without any trouble. When examining the serial number plate, I noticed that the car should be fitted with an overdrive. The previous owner was confinced there was no O/D, but in fact there was. Only, it has not been used for at least 14 years.
Since I use the car quite a lot for touring, I would like to repair the O/D, but I am a bit afraid of the possible concequences.
So here I have some questions for the experts:
The solenoid is broken, but that can be fixed. Is there real danger when I try to engage the O/D after so much time? Can it damage the gearbox or any other part of the driving shaft? Is there a good way to test the O/D other than diving in fourth gear and engaging the O/D?

Thank you for any usefull advice!

09-25-2004, 06:53 PM
Hello, and welcome to this forum. What a fantastic first question. While I can't help you, I know you will get a satisfying answer from somone here.
Again, welcome, and Congrats. on a great year of driving so far.


09-25-2004, 07:31 PM
Please allow me to add my Welcome. Always nice to get another Triumph afficienado on board. Can't address your OD question, but I'd bet on the folks on this forum to be able to help. Good Luck and keep us posted.

Dave Russell
09-25-2004, 08:42 PM
I'll add my welcome to you.
The only real danger would be if you tried to use reverse gear with the overdrive engaged. This would likely break something very expensive inside the OD. There were originally safeguards built into the control circuit to prevent this. (A switch on the transmission that operates when the shifter is moved) Since I don't know what may have been changed over the years, it might be possible to engage reverse while the OD is engaged. Should this happen, the car would be reluctant to back up & if forced, would break the OD. With this one exception, I would give it a try. Just be careful.

09-25-2004, 09:07 PM
Hi and Welcome, I know you will enjoy your TR for years. Not that I can help you much with the overdrive but you have just gotten some good advice about not backing up. Now the solenoid is not cheep and the adjustment is quit critical, do you even have the on and off switch on the steering wheeel, if not you need to check out all the wiring and atlest have a on-off switch. New oil would be nice. Good Luck, Wayne

09-26-2004, 07:43 AM
Hello Slikke,
firstly, what type of overdrive is it, I would guess being a TR4 that it is an A Type, which has a large brass sump plug on the bottom, about 3 - 4" in diameter.
You say the solenoid is broken, in what way or do you mean it is not operational?. The overdrive solenoid has two windings, a heavy current pull in winding which is switched out when the armature pulls in and hits a small switch inside the coil, and a light current hold in winding. It's worth removing the coil and doing a resitance check with a meter, by pushing the little button inside the coil you should see a change from low resistance to a higher resistance. (Sorry I can't give any figures as I don't have any to hand.)
Solenoids are pretty reliable unless mal adjusted so the pull in winding stays energised and burns out the coil.
If it checks out with the meter, refit and manually operate the O\D with the little lever on the opposite side of the casing to the solenoid. The lever has a small hole in the end, there is a corresponding hole in the casing, insert a small 3\16" rod, bolt or drill to hold the lever in that position and adjust the solenoid operating lever (under the 5 sided plate where the solenoid bolts to the casing) so that the solenoid armature is fully in. Then remove the check pin, apply 12 volts to the solenoid, which should click in and ensure that the check pin will re-enter the lever and casing, this is the correct setting.
If this is OK, all that is left is the control wiring, which is a feed from the ignition to the selector switch through a switch on the gear lever control casing which switches when in top gear, and often third gear also, to bring in a relay. There will be a fused supply to the relay which, when energised, feeds the solenoid.
I hope the above is clear enough to let you test out the operational side, and sort out any problems. I would then try running the overdrive, there is a good chance that it will work. Certainly changing the oil is a good idea, and if you do, when drained, unscrew the brass sump plug I mentioned (the O\D shares gearbox oil, in case you did not know) and clean the gauze filter and the magnetic rings.
I will just repeat Dave Russell's advice on not driving in reverse with it engaged and also add that additives of any type should not be used in Overdrive gearboxes.



09-26-2004, 09:20 AM
Whow, thank you for all the kind welcome notes and good advice. This forum and the users are great! /ubbthreads/images/graemlins/laugh.gif

When I removed the drive shaft cover (probably not the correct word, but English is not my native language, so I just translate dutch words), the remains of the solenoid were dangling around on the side of the gearbox. I assume that is not a good sign. /ubbthreads/images/graemlins/grin.gif

Based on your comments I will check and fix the wiring (maybe even test the solenoid, you never know). I already noticed the lever on the right side of the O/D unit, I will test it as described.
The gearbox oil is refreched last year, so I assume that is fine. If all the mechanical part seem to function properly and the O/D still does not work, I might change the oil. But I think it will take a while before I reached that point......

Again, thank you all very much for the good advice. I will keep you posted.


09-26-2004, 01:42 PM
Hello Rienk,
that sounds rather terminal, solenoids are available from Triumph specialist suppliers, maybe you even have some in Holland?. As mentioned they are not cheap but usually last a long while. It could be worth seeing if you can get a second hand (used) one. The A Type overdrive is used on quite a few cars, including my Triumph 2000 saloon car. I know from my club that there are quite a few Dutch members.
As you have clean oil I agree that just trying to run it is worth while.

Alec /ubbthreads/images/graemlins/thirsty.gif

09-26-2004, 04:09 PM
/ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/laugh.gif It works!!!!!! /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/laugh.gif

How about that! Although the solenoid was dangling around it worked when I put 12V on it. So I fixated the solenoid and started checking out the wiring. There were several wires lose, but I was able to find them and connect them the right way (so I hope, making use of a wire scheme of a TR 6 I found on internet). After all that, the solenoid worked again and with my nerves on edge I tried the O/D in third gear /ubbthreads/images/graemlins/tongue.gif. With the click of the solenoid, the revolution counter dropped with about 500 r.p.m.
Never ever before was I so succesfull in repairing things of my TR, thanks to the very good and usefull advice and good quality british products. So after at least 14 years of retirement, my overdrive is now in it's second youth.


09-26-2004, 10:18 PM
Welcome aboard. Happy to hear your O/D works well. If you have any other issues hope we can help.

Webb Sledge
09-27-2004, 12:43 AM
That's great to hear! I want to get an o/d for my 6 sometime down the line. Welcome to the forum!

09-27-2004, 05:21 PM
Welcome, and great stuff on your test. I rebuilt a 4A and never took the overdrive or trani apart although I did the whole car from frame up. Because the trani's are easy to get at we waited until the car could be road tested and then tried the O.D. It worked great at first but then started to slip, result was old gooey trani fluid. Yeah everyone assumed that it was changed but never was, once changed up and the screens cleaned it improved and then we did it one more time and now it works like a charm. Holds 70mph with 2800 rpm. in 4th. Recommend you do change the fluid as it is a quick and easy thing to do and gives you that piece of mind, also a good check on the screen for filings. The mechanic did mention that a good way to help unstick these things is to use Automatic trani fluid for a little while and then drain to replace with the proper gear oil. Anyone else heard of this. Cheers /ubbthreads/images/graemlins/cheers.gif /ubbthreads/images/graemlins/canpatriot.GIF /ubbthreads/images/graemlins/driving.gif

09-28-2004, 07:03 AM
Well, since about all of you mention the gearbox oil, I might as well drain and refill (the cover is off now anyway, so it is easily done). And I am so happy with my new gadget /ubbthreads/images/graemlins/driving.gif that I don't want it to go slipping in near future.
It is probably a dumb question, but I am not sure what is meant by "screens" that should be cleaned (it might just be a language problem, since it also took me a minute to realize that "trani" is short for transmission, stupid Dutch /ubbthreads/images/graemlins/crazy.gif).

Cheers /ubbthreads/images/graemlins/cheers.gif

09-28-2004, 11:45 AM
Congratulations on your discovery. Finding an OD transmission unexpectedly is only just less exciting than below finding the Holy Grail.

"(probably not the correct word, but English is not my native language, so I just translate dutch words)"

Your command of the English language is better than mine!!

09-28-2004, 04:54 PM
Hello Rienke,
the screen is the filter, a metal gauze filter in the bottom of the overdrive. As I also mentioned there are several magnetised rings in the base of the sump plug. Just wash them in some solvent.


10-03-2004, 05:47 PM
Thanks for the explanation. I drained both overdrive and gearbox and cleaned the filter (screen). Since the previous owner was unaware of his overdrive, he also did not take care of it. The filter was mostly blocked with gooey stuff, so it was a good thing to clean the filter and refill the O/D. So far it works perfect and I hope we will get some nice autumn days, so I can use it for a longer drive.