• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Overdrive indicator

Share this page

Tabcon

Tabcon

Jedi Warrior
Offline
I'm having a little difficulty with the overdrive switch in my car. The Healey 3000 I used to have had a toggle switch on the lower part of the dash and it was easy to see when it was engaged. The problem with the TR4 blinker type switch is that sometimes it's on and I don't know it. I suppose I may hit it sometimes before driving and not even know it, then when I shift into 3rd gear, it becomes evident.

I was considering installing a small indicator light somewhere that lets me know when the OD is engaged. Has anyone here ever done that, or does someone actually sell such a thing?

Thanks, and one day when I have learned more about this car, I'll make some contributions to the brain trust. For now though, I'm still ignorant.

Tab
 
I have not done it, but I've often thought it would be a good idea. The TR3A does have a toggle switch on the dash, but I frequently forget to check it. A red LED or similar wired across the isolator switches, so that it came on only when the switch was on but the isolator switches were holding the relay open seemed like a good idea to me.

However, there is also a fellow selling a "logic device" that basically converts the OD to pushbutton operation. It drops out of OD for every shift, then you push the button to engage OD. If you want to disengage OD without shifting, push the button again.

Don't have the link handy, but maybe someone will be along that does. Or it's been discussed here before, you might search the archives.
 
BTW, your TR4 should hit OD in 2nd gear ...
 
I put one on my TR4. Used a blue light just because there was no other blue in the cockpit. My 4 has no heater, thus no heater controls so there was an unused hole in the dash support that was just the right size. Helpful when driving at night.

The light I used was rather like this, though it was readily available at my local CarQuest store:

https://www.speedwaymotors.com/Universal-LED-Indicator-Bulbs,3034.html

You want to get one specifically for automotive applications as a 12V light from Radio Shack (for example) may not withstand the actual car voltage and vibration.
 
I drilled a small hole in my wooden dash below and to the right of the speedo and installed a small round LED light that I wired to go on with the OD. To me, a very helpful addition. The light color I chose was orange.
 
Great. I'm happy to know that it's not just me with this problem.

I think the light is the way to go. I have a spare blinker and generator light set. I was thinking about using the green on and installing it with the chrome matching bezel somewhere on the dash. I tried it below and in the center of the blinker and gen lights, but it looked like two eyes and a nose. I was thinking of removing the windshield washer pump button, which I keep disconnected anyway, and installing it there. Fairly unobtrusive, no drilling required and easy to switch back if I wanted to later.

TR3, since my OD switch is stalk mounted to the steering column, do you have any idea how I should wire it?

I've located the overdrive relay, which is mounted just above the high beam floor button and was wondering if I could somehow wire it to that. I was afraid of shorting something out, so I haven't tried it yet.

Thanks!

Tab
 
Sure, peice of cake,
choose the indicator of your choice, one side goes to the wire that goes to your solenoid from your relay, the other side of the indicator goes to ground.
 
Depending on the relay you have, you may find an unused spade on the relay that is hot when the OD is switched on. Another easy way to connect (if there is no extra lug) is a 2-into-1 spade connector that allows two female connectors to attach to one male lug (the French probably have a name for that).

This approach, of course, only illuminates when the OD is 'on'. What would be more useful in my opinion is a light that indicates that the OD switch is in the 'on' position and would illuminate even if the gear selector is in 1st, neutral or reverse. This is a little more complicated since the column switch is actually switching the ground side, not the hot side -- though it can be done.

The advantage of the latter approach is that it would warn you if you were about to shift into reverse with the OD switch in the 'on' position. Mostly harmless if your lock-outs are adjusted and working correctly but very expensive if they are not.
 
Ah ha!

I spent the last few hours getting all the junk I need to do this, installed it...darn the British must have had really teeny tiny hands in the '60's, and discovered that, as you said, it only lights when you are in an OD gear.

What I was hoping for was for it to be lit whenever the stalk was depressed and in the on position. Reverse was my main problem. Last night, I went to back up and the transmission kept slipping out of reverse. Then I discovered the OD was engaged. No harm though, as reverse and all forward gears and OD seem to work fine. One great thing is that the transmission and OD were professionally rebuilt during the restoration at a cost of almost $4,000.00. I really don't want to run into an expense like that, hence the indicator light idea.

Are you supposed to be able to hear the OD solenoid click, or clank on when you engage it?

Hey Geo, do you think you could possibly provide instructions on how to direct wire it so the indicator light comes on when the OD switch in engaged?

Thanks-

Tab
 
Hard to hear the OD engaging in a moving car/running engine -- but you can switch it on with the engine off and shift thru the gears. You should hear the solenoid click on as you shift into 2nd, 3rd and 4th. You should hear it click off as you shift from those gears back into neutral. You should not hear it click as you shift into 1st or reverse. If it does click on those shifts then the lockouts on the top cover are faulty or maladjusted or otherwise not doing their job which is to assure that the OD does not operate in 1st & reverse.

I will give a think to the alternate wiring of the light to indicate the switch is on. I figured it out once while daydreaming but was blasting down the highway at 85 mph at the time so I didn't make any notes (rather like Fermat's theorem).
 
A friend of mine came up with a place that will make what looks like photo negative with the word overdrive on it. For TR6 you put it it the HAZARD light in the center of the dash in front of the driver. You wire it into the switch for power and it glows with the overdrive on. I have not installed it on my 6 but I will. Sorry about the picture but it's so small it's hard to focus.
 

Attachments

  • 15963.jpg
    15963.jpg
    52.5 KB · Views: 306
Uh oh.

The OD light comes on when I shift into reverse and I can hear the solenoid engage. This is when the car is not running. Also, the OD does not engage in 2nd gear. Apparently the guy who rebuilt the transmission forgot to adjust it properly.

How big a job is it to have this done by someone who knows what they are doing?
Is it something I could do without a bunch of special tools?

Tab
 
It may just be a matter of removing the dash support, then the tunnel to get at the swtiches on the top cover. These can then be adjusted or replaced as needed.

There are 2 switches -- one provides a ground for the relay when 3rd or 4th is selected, the other provides a ground when in 2nd.

OD-Cover.JPG


Those switches are just upside-down push-buttons that are operated by depressions in the selector shafts.

That much is just wrenching, no special tools. Also a good time to check out all the wiring to the unit.
 
Thanks!

That looks do-able.

Would a loose connection cause OD to engage in reverse and not in second gear?

It's very possible that the muffler shop may have knocked a wire loose when installing the new exhaust.

Tab
 
Tabcon said:
Hey Geo, do you think you could possibly provide instructions on how to direct wire it so the indicator light comes on when the OD switch in engaged?
Click to expand...

This may be one way. I must emphasize this is untested and possibly only half thought-out. I need to take a look at the wires from the column switch to confirm this is reasonable. Not an ideal solution, I admit.

Here is the OD wiring on a TR4:

OD%20Wiring.JPG


The column switch provides a ground path that is completed by one of the lock-outs when 2, 3 or 4 is selected.

An alternative to permit the addition of a light that comes on when the column switch is on (irrespective of the gear selected) would be to move that switch to the power side of the relay. I think this may be how TR3s' ODs were wired. Would look like this with the addition of an indicator bulb:

OD%20Wiring%202.JPG


I welcome any input (especially if this will not work or if there is an easier way).
 
I don't know a thing about overdrives, but is it possible that the wiring for the second gear overdrive and the reverse solenoids were switched?
 
Tabcon said:
The OD light comes on when I shift into reverse and I can hear the solenoid engage. This is when the car is not running. Also, the OD does not engage in 2nd gear. Apparently the guy who rebuilt the transmission forgot to adjust it properly.
Click to expand...
This sounds to me like it's not properly wired, rather than poor adjustment. Some covers are also drilled and tapped for a reverse light switch; I think your OD has been wired to the reverse switch. It's even possible your cover has not been drilled & tapped for the 2nd gear switch. When you pull the gearbox tunnel, compare the switch locations to Geo's photo above. That blank pad closer to the top of the photo is the reverse light location.
 
Geo, I believe that will work.

I would be curious to know if the TR4 OD is actually wired with the operating switch on the ground side of the relay (as the factory diagram shows); since at least one diagram also shows the TR3 wired that way, and as Geo correctly notes, it was not.

However, my preference would be for a warning light that only warns of an unusual condition. If the light stays on all the time, I know I am quickly going to forget that it should not be on in 1st and neutral.

So what I want is a light that comes on only when the interrupter switches are preventing the OD from engaging; meaning the operating switch is on but 1st, neutral or reverse gear is selected. I believe that can be accomplished by using an LED indicator lamp (drawing much lower current than an incandescent lamp) wired directly across the isolator switches. The coil in the factory relay is fairly low resistance, so I believe it would pass enough current to light an LED without activating the relay. If not, it may be necessary to add a parallel resistor to the relay coil.
 
I removed the transmission tunnel and this is what I saw.


My overdrive unit

Obviously, there is no switch for second gear. I don't even see the switch for 3 7 4th.

My OD works in 3 & 4th, so what's the deal? Do I need to install a switch in the 2nd gear spot? Why does my OD work with no switch for 3 & 4th and how do I get it to not engage in reverse? Where do you purchase these switches?

I'm totally confused!

Tab
 
Back
Top