Three Fat Tigers

Odds are the OD solenoid is toast, where the wire coil part of the electromagnet has suffered an internal breakdown.

Normally, in a quiet neighborhood, you can lean way over down toward the sill, or lie down under the driver's side of the car, and hear the solenoid on the trans clicking while you/someone operate the OD button (ignition on, engine not running). Otherwise you should be able to put your hand on it and feel the solenoid clicking while it is operated. If you hear/feel nothing, disconnect the electrical connector and test for power reaching that point, best to use an incandescent test lamp (like a brake lamp) that draws some power to verify enough amperage is reaching the connector; or pull the solenoid off and bench test it, touch the wire to the positive cable on the battery and touch the case of the solenoid to a ground point; again it should click. No power at the connector would indicate the relay where in rare cases the relay can burn out a contact or suffer a failed solder joint while still allowing the dash light to operate normally; simple to pop the cover off the relay and have a look; although a bruned relay contact failure is usally caused by a defective solenoid or the wiring to the solenoid shorting to ground.

Odds are attempts at cleaning out the solenoid will do nothing for it, but you might try some carb cleaner, then bench test it. Should the solenoid need to be replaced, it can be expensive new, same part is used on all 240/740/940 with similar transmission; going with a used part can be hit or miss as this is a common failure.

You can also take the defective solenoid and cut a channel between the holes, this would allow the OD to stay available, it will still downshift out of OD when you give it throttle, you just won't have the option to manually turn it off. Use a drill bit and drill in the holes at an angle to cut over into the groove (mounting it in a vise helps), the idea is to create a fluid path between the holes, the metal is very soft so it's quick and easy to do (note this might actually work without the drilling if you just reintall minus the center o-ring, though I've never personally tried it that way). Reinstall minus the center o-ring, RTV sealant on the large o-ring should be sufficient, you can cut the wire off the solenoid as it won't be needed. To access: jack up the entire driver's side of the car, clean the area around the solenoid first with brake/carb cleaner +rags to minimize dirt contamination, remove the two bolts (12mm, flex head gearwrench works best) be ready for some fluid leaking out, but it shouldn't be too much. If the outer larger o-ring is too old it may be rock hard, but it will still work with some RTV if not broken. It's an odd size so finding an exact replacement without a trip to the dealer might be difficult, you can take a larger diameter o-ring and cut out a section where the remainder joined together will complete the correct size, then glue the ends together with super glue; this plus RTV should work fine.


For reference:
Driver's side: http://www.threefatt...reOutSide2c.jpg
Solenoid: http://www.threefatt...Dsolenoid-1.jpg
Modify: http://www.threefatt...olvo/ODmod1.jpg
As on the 240: http://www.threefatt.../ODsolenoid.htm

FCPGroton likely has the best price on a new one:
http://www.fcpgroton...category_id/208

The vacuum line is an hard plastic line that runs through a rubber grommet somewhere below the the firewall heater hose connections; from there it goes to the control panel (if you have MCC, manual controls) or to a solenoid valve pack mounted approximately behind the glove box (if you have ECC, electronic controls)

IIRC vacuum applied to that valve causes it to close.

Are you saying that the lever won't move over to the left into the reverse gear plane?  If so the guide bolted to the top of the shifter support cage (up under the shifter boot) is likely loose or somehow out of position.  When you lift the detent collar, it lifts a block, that is built into the shifter, up and above the guide so that the lever can move over to the left. There is no electrical component, micro switch or otherwise, that would prevent the shifter from moving into position.

If the lever is moving over to the reverse gear plane but when you push forward it won't go in, try putting the shifter into 4th gear, then directly into reverse.

Otherwise it might be failed shift linkage bushing where the shifter can't quite twist the shift rod enough. Or the clutch might be dragging; try putting it in a forward gear on a level road and if the car creeps forward, it is dragging.

Yeah I should have mentioned that you might have to hold it above idle while going through the injectors.