Overdrive issues

[Mike Stevens]

There is a switch contact on the top of the solenoid as the solenoid has 2 windings one is the main pull in coil and the other is the hold coil as you need a large amount of power to get the solenoid to pull in but once it is in it requires very little current to stay there.

True for the 'A' type but not the 'J' type. The 'J' type operates directly on the hydraulics and draws much less current. In fact the 'J' type doesn't use a relay to operate the overdrive but I think it should as the gear lever switch would probably last longer if it did!

What I find confusing is that the OP said that he's wired a lamp in place of the solenoid and it operated OK, but not with the solenoid connected. This can only imply a fault with the solenoid - but it's been replaced (and the 'J' type ones are not cheap!).

Maybe do some resistance measurements of the solenoid itself and also try it 'on the bench'.

Cheers,
Mike.