Now that this is a discontinued part, no one has them. Does anyone know of any secret source with NOS? Does this mean the junkyard is the only way to keep the M46 going? Are their british tranny's with similar solenoids?

 

the overdrive on a m46 is a Laycock J-unit, same as many british sports cars from the late 60s, early 70s.

a solenoid is just a electromagnetic coil with a iron or magnetic slug inside, energize the coil and the slug is pulled in or out depending on the design. if the coil is burned out, it should be possible to rewind it, you need the right gauge enamelled magnet wire, and the correct number of turns, winding is usually done with a motor spinning the spool form at an even speed so you can carefully layer the windings. when you remove the original wire, count how many layers are wound around the form and how closely packed they are (how many turns per layer), if you reproduce this, you should get the correct inductance for it to work.

 

Welp, if that's my only option I'm screwed, because it will take me 5 years or so to get around to doing that. Any other options besides winding my own coil?

 

well, whats wrong with the solenoid? are you SURE the solenoid is the problem?

we had a TR6 that had a J overdrive, and the OD itself needed rebuilding at some point, I don't recall the solenoid was ever a problem. on the TR6, the OD switch would fry itself, the solution was to add a Bosch relay between the switch and the solenoid, but I'm pretty sure the Volvo already has a relay in the circuit.

 

Good point...I'm not 100% sure, just going off what my mechanic said. The OD goes in and out of 5th gear randomly. Asked him to diagnose it and he said it was the solenoid. Any exact tests I can do to rule it out?

 

is the dashboard light reliable? it comes on and goes out consistently when you toggle the button while in 4th gear? or does it blink with the OD going in/out randomly ?

if it blinks with the random shifting, then you have an electrical problem upstream.

find connector "E", this is a 3 pin flat connector on the right side of the transmission tunnel under the carpet and somewhat forward of the shifter, pin 1 is black on one side and brown on the other, pin 2 is yellow, pin 3 is red. the 'forward' half of this connector goes to the OD relay and rest of the car harness behind the dashboard, while the rear half of the connector goes to the OD solenoid and OD shifter switch and gearbox switch.

yellow wire on pin 2 goes to the OD solenoid, the other side of the solenoid is a black wire thats grounded on the bottom of the OD unit under the car. the red wire on pin 3 comes from the gearbox switch that tells it you're in fourth (this gearbox switch grounds that red wire if it is in 4th, otherwise the wire 'floats').

Assuming the dashboard OD light is toggling as expected, I would be looking for signs of damage to that yellow wire, or the black ground wire under the OD unit under the car.

 

the other thing I would do if you get this far...

pull that solenoid out of the car (probably have to drain the transmission, and for sure clean the area around the OD solenoid really well before removing it, any grit gets into the tranny, its death). clean it, visually inspect it. hot-wire 12VDC to its leads, and verify that the fluid openings open and close as you connect/disconnect power. I believe it looks like this?



when its 'open', I believe I would try to blow it out with a compressor.

 

these guys claim to have 4 in stock.
SKANDIX Shop Volvo parts: Solenoid, Overdrive Typ J 1232101 (1001129)

 

Thanks for your help Pierce, per my son, the light matches the OD going on/off randomly. So we will follow your advice on tracking down the electrical fault....sometime, soon, hopefully.

 

does the light and OD unit ever engage when its not in 4th gear ?

does the light and OD unit ever engage when it is in 4th, but the switch is off?

does it ever blow fuse 11?

here's the wiring diagram.



I surmise there's at least three possible failure modes...

1) the switch D on the shifter **** or its wiring is intermittent.

2) the OD relay is bad

3) the wiring to the solenoid is intermittently shorting to ground, or intermittently broken/open.

 

the parts locator to go with that wiring diagram