Overdrive wiring

[autoheart]

Hello all. I'm installing an A-type o/d, recently rebuilt by John Esposito, in my TR4A (which never had one before). I have all the bits, but I can't figure out where the o/d relay is supposed to mount in the engine bay, and where the harness is supposed to go from the o/d to the relay. And while I'm at it, where does the speedo cable route?

 

[pa297pass]

Hi Joel, welcome to the Forum.

I can't speak to the TR4a, but on my 1962 TR4 which came with overdrive from the factory, the OD solenoid is mounted in the interior, on the passenger side.

Here is a picture taken looking up into the passenger side footwell... the OD solenoid is to the left side of the picture with the yellow wires coming out of it.

Hope this helps.

Matt

 

[autoheart]

Thanks, Matt - especially for the photo. I suspect this is the same on the 4A. So there's a harness that penetrates the firewall in front of the relay? And the wire bundle from the o/d itself goes ???. I'm totally befuddled.

 

[pa297pass]

Joel:

Unfortunately, my car didn't still have the OD transmission when I bought it, so I don't really know where the wiring goes from the solenoid. There is no hole in the firewall in front of the relay. I will take another look at my car tomorrow and see if I can decipher anything.

Matt

 

[TR4nut]

Assuming a 4a is just like a 4, the wiring goes through the trans cover itself. On my 4, there is a grommet on the cover about 9" off the floorboard, and 2.5" from the firewall. I have the same location for the relay as in Matt's picture.

Welcome to the forum, by the way!

Randy

 

[MichaelG]

Yes the 4A and 4 are similar.. Solenoid as shown in the picture and wiring harness through grommet in the transmission cover. No wiring goes through the firewall.

Are you replacing the transmission tunnel? There are a couple of mods you might need or want to make. I had to cut out a small area over the 90 Degree speedo connector coupling in order to make the plastic replacement cover fit. Also, the workshop manual shows a cutout that provides access to the solenoid from inside the car...access to both of these would make it much easier to diagnose future O/D performance issues.

 

[autoheart]

Thank you everyone - this is most helpful. I assume the grommet is on the right side of the tunnel? I'm not replacing the tunnel. I have a plastic one, and plan on making an access panel for the solenoid, as well as any other mods that may be necessary.

I also assume the speedo cable goes over the top of the tranny then down into the right angle - is that correct?

 

[TR4nut]

Yep, grommet is on passenger side. On the TR4 (and I think on the TR4a) speedo cable is quite a bit longer than the non-od cable. Cable routes from speedo to outside firewall, then behind engine, then down the right side underneath to the tranny. I believe there usually is a clip on the cable that mounts it to the outside firewall right behind the engine, but that one is a real pain to install and I don't think is critical.

Randy

 

[autoheart]

Perfect! Thanks again.