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TR4/4A TR4 Overdrive Solenoid

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Alex_McMillin

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I had an type-A overdrive transmission rebuilt and installed a couple years and it was great. Fast forward to today, and the overdrive is nolonger engaging. With the car turned off and in 2nd, 3rd, or 4th gear I can hear a "click" when I flick the overdrive switch. I am wondering if this means my solenoid is kaput. If so, where is the best place to source out a new one? Is the aftermarket one from Moss any good?

Alex
 
I'm working on the overdrive for my single rail Spitfire transmission. My thought is if you're hearing a click, that may be the sound of the plunger moving in or out - meaning it is working. I've noticed, too, that the overdrive seems sensitive to low transmission oil. I've had good luck with parts ordered from Moss, Spitbits, and The Roadster Factory. Some of the solenoids seem a bit pricey.
T.T.
 
It is possible it is out of adjustment. Not moving the arm far enough to operate the plunger that lifts the ball that lets the oil into the pistons.

Have you checked the oil level/changed the oil recently?

I got a new Solenoid from either Moss or TRF and it works fine.

David
 
Thanks for all the replies. Great info. What oil are we talking about? Transmission oil? Our is there something else I'm missing?

I'll lift and have a look at it today.

Alex
 
The overdrive and transmission use the same reservoir of oil. Check for adequate oil in the transmission, in the usual way, and that will take care of the overdrive too.

When you say you hear a click--is it a little click or a serious clunk? The overdrive solenoid is operated by a small relay, and if the solenoid isn't working, you might just be hearing that. The solenoid itself makes a much louder sound when it operates; the two should be easy to distinguish.
 
Triumph put out a manual on the overdrive with an excellent section on troubleshooting steps. Electrical is my weak point, but I was able to figure out mine and get it working again with a multimeter, including which wires went where on a new relay. The relay that was on my car, though it worked at first, had no physical resemblance to what was supposed to be there, and none of the letters. Obviously, the previous owner had better electrical skills than me. Taking the tunnel cover off was also a great help to test the switches on the transmission.
 
My overdrive started engaging slowly last season (i.e. 2-5 seconds to engage). Gear box fluid is topped up. So, I strongly suspect the solenoid needs adjusting. I did my research and the adjustment instructions are not consistent.
  • Standard-Triumph Manual (TR4 w/ TR4A Supplement) states to use the 3/16" rod method but specifies to adjust the valve to open 1/16" beyond this point: “…so that when the solenoid is operated, the lever will be pulled approx. 1/16” beyond the point at which the shaft is held by the 3/16” locating peg.”
    Haynes Manual, Bentley Manual and LayCock Manual all state to use the 3/16" rod method
In the end, I tend to agree with Titanic, you may need to open the valve beyond the 3/16" rod method due to wear or specification changes. I hope to get under the car next weekend to inspect this adjustment. Here is a link to a great video from Weg's Garage showing him performing the adjustment per the Standard-Triumph Manual:

The Buckeye paper is probably technically the best way to do the adjustment, but, requires a dial indicator mounted - and I am not sure if that means the trans needs to be on a bench.

Bob
 
Bob-I agree. The adjustment is easier to make on a test stand with a dial indicator, but that kind of precision probably isn't necessary. I think the bottom line is that if the OD isn't engaging using the 3/16" rod method, try increasing the valve opening slightly. Having said that, I did do mine on a test stand with a dial indicator, mainly because the trans.&OD were being rebuilt. I ended up with the valve opening being about .025".
Berry
 
Berry, after you did the bench dial indicator setting, did you check the 3/16"rod to see if it was the same, or was there a difference?

Graham
 
I've set mine to 0.020" ball lift on the operating valve and it has worked very well. When I checked the lever to pin hole I've found it to be just short of 1/2 pin width off, meaning using the pin to set the solenoid the lift was not measured at the operating valve and required the lever to be pushed further to unseat the valve. the Healy guys that use an A-type set the lift at 0.040" and Buckeyes pages recommend setting at 0.016".

I have also not noticed a hard hit when the OD engages but I do use the OD like Randall (RIP) did recommend feathering the throttle or using the clutch.

edit: I do bench test and set the OD before installation. MT 90 here too!
 
Graham H said:
Berry, after you did the bench dial indicator setting, did you check the 3/16"rod to see if it was the same, or was there a difference?

Graham
Click to expand...
Graham-It has been quite awhile, but I believe the setting was more than just using the 3/16" rod.
Berry
 
Hi everyone,

Thanks for all the info. Great reading and helpful. The Wegs Garage video was really nice. Great to actually see the adjustment than reading and trying to picture it. It turns out I had way too much play in my solenoid actuating arm. I adjusted basically the same as Wegs and voila! Instant gratification when I flicked the switch and heard, not just a small click, but a significant clunk. And my test drive confirmed everything. The grin on my face was quite large. It is so nice to have this functioning again. The car just cruises along very comfortably.

Thanks again everyone.

Alex
 
That valve adjustment can be tricky, and as you see above, there are lots of different opinions on what's right. I used a dial micrometer but I had some trouble getting consistent readings until I realized that I had to push the valve back manually after operating it; it didn't return by itself unless there was hydraulic pressure behind it.
 
Alex,
That's great news. BCF for the win!

I finally got under mine too (overdrive engagement was delayed ~5 seconds). It turned out that the rubber dustcover on the solenoid became brittle, cracked and folded up and restricting the free movement of the solenoid rod (I guess after 21 years that's not surprising). After removing the dustcover, cleaning and lubing everything the overdrive worked like normal again. I don't drive in bad weather or rain so, I am not worried about a missing dust boot.

Bob
 
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