TR4/4A TR4A Overdrive Relay

[rlich8]

Hello all,

My TR4A was converted to OD at some point, which is great. The switch is proper and the OD works great, but I have a few questions.

The OD is supposed to operate in 3rd and 4th gear only, correct? I can switch it on and off in any gear (including reverse! EEK!), which I know is not right!

I am suspecting 1 of 2 problems:
1. The lockout switches are incorrectly wired and perhaps the circuit is closed all the time.
2. The shift tower somehow got swapped from a standard non-OD transmission, thus, there is no switching.

Also, where is the overdrive relay usually located in the TR4A? In the TR4A, is the overdrive harness built into the main wiring harness of the car? How many switches, total, should be on the transmission? There should be a switch on 3rd, and 4th gear, correct?

Thank you!!!

 

[TR3driver]

You should have OD in 2nd, 3rd & 4th. Two switches on the gearbox, one above the 3-4 rail and another above the 1-2 rail.

There are several different styles of switches, so don't worry if yours look different than mine

 

[Geo Hahn]

And the relay is at the bottom center of the battery box (inside the car) just above the gearbox's bellhousing. The OD wiring harness is separate from the main harness.

 

[hondo402000]

you could also have a problem with one switch stuck in the closed position, have you checked the switches with a volt ohm meter. the reverse switch in my TR6 was stuck in the on position and the Previous owner just un pluged the wires instead of fixing the problem, and FYI the switchs are located opposite to where you think they are first gear is left and up, so the switch is in the right and back position, I think I got that correct

Hondo

 

[Geo Hahn]

Should look something like this (though this one has no reverse lamp switch):

 

[rlich8]

Perfect, thank you gentleman. This is exactly what I needed.

I was able to pull off the radio console, and the rubber boots, and I can see the switches, so that's good (no one swapped out the shift tower/extension.)

I will pull out a seat and the trans tunnel this weekend to diagnose further.

Let's hope the relay is in the correct spot!

 

[rlich8]

HA, So...

Today I got ambitious and took out the seats and trans tunnel. Alas, there is NO overdrive harnesses at all. They literally just stole power from the ammeter, ran it through the switch, to the solenoid. NOT done very well...

So, I called up John at Quantumechanics and bought the wiring harness from him. I'll be ordering new gear switches as well.

Soon enough, this'll be a properly functioning system.

 

[TR4nut]

Is this an A type overdrive? It should be but if a J type were installed it would at least explain the lack of relay. Sounds like bad wiring either way, however.

 

[rlich8]

Is this an A type overdrive? It should be but if a J type were installed it would at least explain the lack of relay. Sounds like bad wiring either way, however.

It's definitely an A type overdrive.

Just wired really, really poorly. I'm surprised the overdrive stalk switch hadn't burnt out by now. Anyways, I've ordered all the bits to properly finish the job. Thank god there was nothing ruined here.

 

[Marvin Gruber]

Years ago before I knew better I ran an overdrive wiring direct thru the sw, never had any problems. The wiring is easy so why risk it.

Marv

 

[TR3driver]

Oddly enough, early Stags had an A-type with no relay, too. Different switch of course, but it was a puny little slide switch.