General TR D Type overdrive not working need suggestions

[JKB1957]

I was out on a drive a couple of weeks ago and the O/D in my Spitfire stopped. Got home, looked under the dash and plugged the O/D wires back together, and still no O/D. So out with the trans tunnel. First check, wires are all connected as they should be. Step two, oil is full, 30 wt, non-detergent. Step three off with the side over, adjust actuating level, make sure solenoid working it should. Step four pull operating valve, clean, replace spring.

Test drive today, car ran perfect, but no O/D.

So, any thoughts on what I should check next? Or should I just pack it up and send it away for a rebuild?

 

[TR3driver]

I've never worked on a D-type, but I think you can access the pump non-return valve, and pressure relief valve without removing the unit from the car, through plugs on the bottom. Might be worth cleaning them, although any significant dirt probably means it's time for a rebuild anyway.

 

[JKB1957]

Problem solved. I went back and checked all of the electrical connections, everything was perfect. Then I pulled the cover off the actuating lever. No movement. Played with the solenoid push rod and got it to work. On the road, nothing. Pull the cover again, play with the actuating level and very small movement. Diagnosis, bad solenoid. Next problem replacing the solenoid on a "D Type" overdrive. I've done it once, less then 2K miles ago on this car. I've also had kidney stones. It's a toss up as to which is more painful. Later.

 

[TR3driver]

Just a thought, I found that the replacement solenoids (my A-type takes the same as your D-type) don't last nearly as long as the originals do. I'm not sure yet how much it will help, but I added a diode across the pull-in coil contacts in the end of the solenoid that should, at least in theory, make the contacts last longer. The same approach worked a treat on the operating relay. I had 3 different replacements (including an expensive reproduction) fail within a year; but now with the diode the same "cheap Chinese" relay has lasted almost 20 years and still going strong.

 

[Don Elliott]

The solenoid in my 1958 TR3A failed when I was at VTR in 2000 in Portland Oregon (7300 miles round trip) so I ordered a new one from Moss in California. It worked about 5000 miles and then failed. I had since repaired my original (cleaned the contacts and soldered a couple of tiny wires) so I put that one back in. I took the "new" repro from Moss apart and found a lump of white RTV rubber wedged in between the internal contacts. They had put too much in when they built it and the RTV piece (the side of a large green pea) was the cause. I pulled it out and this repro solenoid is still my spare - just in case.

 

[JKB1957]

That's a good idea. Thank you. I also found a site that suggested using a long bolt underneath the solenoid to make it easier to replace.