First a bit of background....
Most of us know that the overdrive / torque converter lockup function on various 740 940 etc auto transmissions can have a fault where the operation fails and the gear change will not progress past third. This is often due to one or more of- faulty switch on gearshift, faulty wiring ( commonly at the rubber on the solenoid itself ), faulty fuse 12 ?, faulty relay ( most common of all ), or faulty solenoid valve. A permanent solution can be to modify the existing solenoid so that it is always open or replacing the solenoid with a bypass plate like IPD sell.
The Bundy bogan solution....
My daughter picked me up in BrisVegas, for the trip home to Bundy in her 940. She was driving. The first thing I noticed was that the front number plate was more mangled than usual. ‘parking by touch again ?‘ She just smiled.
When we hit the freeway, I noticed the car felt like it was in third. She was doing approx 100 and the revs were about 4k from what I could see. I pushed the button on the gearshift, but it made no difference. I asked what gear she thought the car was in, she said 4. I asked how she knows that, and then she pointed at the tacho- it says 4. After i finished laughing, I told her that was 4000 rpm, not 4th gear.
I asked how long it’s been like that, and she said – ‘a few months, buts it’s ok, I just turn the stereo up so I don’t hear it’.
( By the way, this is a true story that happened yesterday. )
When we had a chance, we pulled up at a rest area, and parked the car over a gutter so I could slide underneath. Everything looked as it should, no loose wires. We then checked the fuses, all good. We then pulled the relay, and took the cover off, and then applied the Bundy bogan trick – one zip tie that permanently closes the relay contact. Put the relay back in position, and drove off.
Like magic the tranny shifted into 4th, and then into ‘ overdrive ’ for a comfy ride home at 2500 rpm. So the problem was with the relay, which should be the first place to look; In fact I could have done this fix from the passenger seat while she kept driving.
( If the zippi didn’t work, I was thinking of running a wire from the cigarette lighter power supply, out the door, under the sill, and connect direct to the solenoid connection, so it was permanently powered and bypassing most of the electrical problems. Not the most elegant solution, but better than driving for 4 hours at 4000rpm. )
Pics of fuse box access , and the zip tie bogan relay.