J Type Overdrive issues

[Radders]

Why would an overdrive cut in and out of its own accord???

You can be hurtling along the motorway at erm.........70 mph (we'll say) and all of sudden it will change itself down!

Any ideas?

[Jason]

The last time that happened to me it was a broken wire, inside the insulation, it had gone brittle with the heat, the insulation had cracked and then the wire corroded inside. Replaced easily and all sorted.

[rotoflex]

It sounds like an electrical issue to me, too.

If the OD switch is off when this happens, I would look at the schematic to see a likely spot for an electrical fault to complete the circuit to the OD solenoid.  

It may be a bad switch, wires connected to the switch shorting, or something interesting at the relay.

[Pete Lewis]

if it has the switch on the gear knob the wires inside the hollow stick fracture, use silicon sheathed wire to cope  with the heat   Pete