TR2/3/3A TR3 overdrive question

[TFR]

Where does the OD activation solenoid mount? I know where the transmission solenoid is located, this is the solenoid with for wires.
Also, where does the wiring run from inside the cab to the fuse panel and regulator. Through the harness grommet?

Thanks for your help again...

 

[TR3driver]

The relay mounts to the rear surface of the battery box, under the dash. Here's a (poor) scan from the workshop manual/Bentley.

The OD wiring did not originally run to the fuse panel & regulator. Instead, the power for the solenoid comes from the back of the ammeter (battery side, oddly enough), while the power for the relay coil comes from the white wire terminal of the starter pushbutton (through the operating switch on the dash). Then two wires go from the relay to the gearbox, I believe under the carpet and through a grommet on the LH side of the tunnel. One from the coil to the lockout switches on top of the gearbox, and the other from a contact to the solenoid.

I know, several sources show the operating switch on the ground side of the relay. But what I've described above matches what I found on TS39781LO (with original-looking wiring in sub-harnesses), and makes more sense than the scheme given in the book (which requires an extra run of wire from the relay to the dash).

PS, it also matches what you can see in the photo

 

[Geo Hahn]

The relay mounts to the rear surface of the battery box, under the dash...

To state something obvious... if you go do drill two holes for mounting screws for that solenoid remember that your battery is on the other side of that sheet metal.

 

[TFR]

Obvious or not, I thank you for the reminder.

As for the power source and relay power I think it might be best on a driver to find the most reliable location. Perhaps the most reliable may be the above stated locations.

Thanks for all your help... again.

 

[Harry_Ward]

Randall is right on with the location. Here's the first photo I posted on BCF. I ran the wires for the OD solenoid up and then to the back firewall so they came down along the firewall in the squared off corner to the right side of the gas pedal down and then along the floor tight against the tranny tunnel then up to the hole on the left side of the tranny cover. make sure you have a rubber grommet in the hole or the wire will wear and short. That's how and where the original solenoid wiring harness met it's fate in my car.

 

[Don Elliott]

My relay for the overdrive is the original one that came with my 1958 TR3A. It has screw-on terminals. There are two flat-head screws which are in two holes in the lower corner of the battery box. The flat heads are on the battery side and are MIG welded & ground smooth on the flat-heads not to make an indent in the back of the battery. I also use a piece of 1/16" thick rubber on the back of my battery to take up any irregularities with these flat-head screws.

When I replaced my battery box, the box was about 1/2" shallower than the original box so I had to make an adapter plate to lower the relay so it would not interfere with the heater.