TR5/TR250 Overdrive question

[arbs_53]

I finally got around to installing my overdrive and I'm curious about something. The car is up on stands, the driveshaft is not connected to the rear flange and the speedo cable is not yet hooked up. After searching the internet for information this past weekend, I believe I have it wired correctly. Tonight, I started the car and got it to about 3000 rpm in 3rd gear and hit the overdrive switch and the solenoid switched upwards, but I didn't notice any reduction in rpm. Does this mean something is not right?

 

[TR3driver]

Possibly, but most likely not. With the output not connected to the ground (and hence the mass of the car), the OD output will speed up rather than the engine slow down. Try connecting the speedo, so you can see the speed jump upwards when the OD engages.

Or an alternate test, if you can't use the speedo for some reason, is to connect a timing light to the engine and use it to 'shoot' the output flange. In 4th gear direct, you should see the flange stop under the timing light; then go back to moving when you engage the OD. If I remember correctly, it looks like it is turning backwards in 4th OD, because it is actually moving 2.44 turns per flash; which your eye interprets as -0.06 turns

 

[TuffTR250]

I believe the best way to ensure that the overdrive is functioning correctly is to get an overdrive pressure gauge. You will see the pressure increase and decrease as you engage the overdrive, even if the driveshaft is not attached. That is also the best way to "tweak" the adjustment of the overdrive levers to ensure that the overdrive is kicking in when the solenoid is activated.
Regards,
Bob

 

[TR3driver]

I agree about the importance of a pressure test; I wouldn't consider installing an OD without doing one. However, I wouldn't consider it a compete test either. For example, the OD clutch might be jammed such that the unit stays in OD continuously, and the pressure could still appear normal. This is a serious problem, as backing up with the OD engaged will destroy the sprag clutch and frequently the rear housing as well.

Personally, I prefer to adjust the lever by measuring actual movement of the ball. The pressure test may appear normal with a very small movement of the ball (which some feel is a Good Thing but I don't). And if the ball is moving by less than .015" or so, it may fail to lift off the seat under some circumstances, resulting in a unit that doesn't shift reliably. The linkage to the ball is somewhat flexible, and it has to lift against full hydraulic pressure. A larger movement ensures that the full force of the solenoid is available to lift the ball.

Here's one source for the special adapter needed to connect a pressure gauge:
https://www.geocities.ws/jholekamp/
I made my own as a lathe project, but obviously that's not for everyone.

 

[TuffTR250]

Randall, how do you go about measuring the movement of the ball? Also, I was thinking that if the OD clutch was jammed that the pressure would not drop when the OD switch/solenoid was shut off, is that not the case?
Regards,
Bob

 

[TR3driver]

Randall, how do you go about measuring the movement of the ball? Also, I was thinking that if the OD clutch was jammed that the pressure would not drop when the OD switch/solenoid was shut off, is that not the case?

Basically just a dial indicator, with a length of brass tubing over the tip (so it rests securely on top of the ball). You have to be careful to lift the solenoid plunger into place by hand before energizing the solenoid, don't want it banging up the indicator movement. There is more info at
https://www.buckeyetriumphs.org/technical/AOD/AOD4/AOD4.htm and https://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf

I've not actually had a clutch stick, let alone be able to take measurements with it stuck. But I believe there will still be a small pressure drop shown as the pistons move a bit to take up the play (and flex) in the linkage to the clutch. Someone who is accustomed to working on these overdrives would likely know the difference, but it's a hard thing to describe to someone who has never done it before, especially since the amount of the drop depends both on how much wear is in the clutches and whether you have a large or small accumulator unit. Of course, I could be wrong, but if it was my car (and my back installing the gearbox), I wouldn't care to take the chance. I find it really aggravating to have to repeat a lot of work because I skipped a minor test.

PS, Enco almost always has a cheap dial indicator and magnetic base on sale for under $25. I don't use mine very often, but it is still working fine after many years of ownership. I keep the magnetic base clamped to a steel plate when not in use, which might possibly help preserve the magnet.
https://www.use-enco.com/CGI/INPDFF?PMKANO=385&PMPAGE=7&PARTPG=INLMPA&PMCTLG=01
(If that link doesn't work, go to https://www.use-enco.com and look through the HOTDEALS section.)
I can't prove that Enco is any better than HF, but I do like them better. If nothing else, they list the better quality tools right next to the cheap junk, so you can decide which you want. If you would rather have Starrett quality, they also have those at a reasonable price (for the best available).

 

[TuffTR250]

Thanks Randall!
Regards,
Bob

 

[arbs_53]

I'll admit to being a little dense when it comes to understanding how these things operate, so I appreciate everyone's help. I want to do the pressure test, but I've seen warnings to first release any pressure that may have built up when I had the engine running in 4th, on stands, at about 30 mph and the O/D switched on. Solenoid moved up, but no change in rpm or speed. I tried manually operating the switch lever on the passenger side to see if the O/D would engage, but nothing happened. So I don't know if there is any built up pressure or not.
I'm also wondering if I have the wiring correct and if that could be causing some of my problems. I took a picture of the O/D relay, it's the one on the bottom. The white wire is fed from the ignition switch, the brown is fed from the starter solenoid. The rest of the wiring is as it appears on the wiring diagram. I have 4.2 pints of GL4 80/90 hypoid oil from TRF in the unit. The unit was supposedly completely rebuilt a couple of years ago and never installed. I purchased it on E-Bay from a guy who bought it for his TR-6 that was totaled before he had a chance to install it. Don't know if all this helps. Any suggestions on what to try next will be greatly appreciated.

 

[TR3driver]

If the solenoid plunger went all the way to the top, then at least your immediate problem is not electrical. Pushing on the lever also bypasses all of the electrical stuff, so that's more evidence you have a hydraulic problem.

Loosen the plug a turn or so, and see if it still seems tight. If so, there may be pressure behind it. If you can't bleed the pressure off by pushing the arm down (past where the holes line up), then just leave the plug loose overnight and let it bleed off through the threads. My guess is that you have no pressure, though.

There are some step-by-step troubleshooting instructions at the link I gave above.

PS, like so many things, you have to work one step at a time. Get the hydraulic stuff sorted, and then you can check out whether the electrical is all working as it should. Sounds like it is probably OK, but make sure the lockout switches are doing their job.

e Bay is like the ultimate used car lot. "No, ma'am, that's yellow primer."

 

[glemon]

One time, when I had just reinstalled an O/D and tranny after a transmission rebuild and the O/D didn't work I talked to an old foreign car mechanic (the old applies both ways, old guy, works on old foreign cars mostly) and he suggested I fill the tranny with the car jacked up quite a bit in front to make sure the oil flows back into the O/D, I tried this and it worked. May or may not be your problem, but a pretty simple thing to try. I know they can fail mechanically, but in my nearly 30 years of owning cars that have Laycock overdrives they have been very reliable mechanically, I haven't ever had a mechanical failure, but have had a number of electrical ones, and a couple times low oil issues.

 

[TFB]

I finally got around to installing my overdrive and I'm curious about something. The car is up on stands, the driveshaft is not connected to the rear flange and the speedo cable is not yet hooked up. After searching the internet for information this past weekend, I believe I have it wired correctly. Tonight, I started the car and got it to about 3000 rpm in 3rd gear and hit the overdrive switch and the solenoid switched upwards, but I didn't notice any reduction in rpm. Does this mean something is not right?

Similar issues with adjustment of lever on my also ebay rebuilt unit.When I called builder he said new cone clutches have a tendency to stick until engaged and disengaged a few times..He said go under the car and tap on the large ring flange of od ,engine off,unil and you will hear clutch release if stuck.I did this,heard it release,and then started car and flipped into od,and it stuck agin.Tap loose again,flip in and out a few times and everthing worked and continues to be ok..
Good luck,
Tom

 

[arbs_53]

Does this operating valve looks like it needs to be replaced? The picture with the ball valve shows a nick at the 5 o'clock position, if 6 is straight ahead. The picture of the spindle shows the nick at 8 o'clock. I'm waiting on a few parts for my dial indicator and pressure gauge so I can carry out these other tests. In the meantime, I'm wondering if I need to ground the body of the solenoid if I want to test the current draw? The Buckeye Triumphs' article mentions they held the body of the solenoid against the negative terminal of the battery. Do I need to ground the body (jumper cables to negative post?) if the solenoid is installed?

 

[TR3driver]

It's a bit hard to tell from your photos, but it looks to me like the nick is entirely outside of the band where the ball contacts the spindle. If so, then I'd say it is fine.

The solenoid definitely needs a return path to the battery. But if you have it already installed in the car, then the usual path through the gearbox, engine, ground strap at the LF motor mount and so on should do. Still, if you have any doubts about that, then adding an extra temporary jumper certainly won't hurt either.