I have a 1987 raider with auto trans that will not upshift into O/D. The O/D on-off button lights the dash indicator but no up or down shift. Other than that, the trans works very well... good shift timing and very good shift feel. Trans engages in drive or reverse firmly and quickly.I have about 40 miles on rebuilt 2.6. Prior to that the truck was not licensed since 1998. Any ideas on whats up with O/D? Fluid is clean and nice cherry red... no discernable odor. Also tach is not working so I cannot watch for RPM variance.

The od is electric valve controlled. There's a wiring harness from the engine compartment down the trans tunnel underside to the od solenoid valve on the top of the tranny. There's a connector to check near the tunnel/firewall area.

Second, od enable is controlled by a temp sensor on the engine, behind/below the distributor cap. There are several sensors there. The one you want will have a single wire connection, and be one of the smallest. If the sensor is bad, grounding the sensor wire should enable od. You should see 12v at the sensor wire with ign on and od switch on.

Report back....

Thanks fasteddy for the info. I will check it out this weekend and let you know.

Just got finshed troubleshooting the no OD situation.I found the wiring harness and switch on the pass side of the tranny, traced it to the connector at the fire wall(sort of behind the air cleaner,right?) and then to what I thought might be the temp sensor sort of up by the dizzy. I turned on the ignition with OD on. At the temp sensor,my test light would blink on and off in a rythmic manner. I then checked for continuity at the firewall connector and the plug on the tranny. The test light would barely glow as if the voltage was very weak at these two locations. Oddley, I had noticed this same condition a few weeks ago on the ballast resistor on the coil. One side of the resistor would be very bright, the other side is noticably dimmer. I ground the wire from the sensor and on my test drive saw the temp gauge was maxed out. Once I removed the jumper wire and plugged the wire back on the sensor the gauge returned to normal. Whew... Oh yeah, also now I find that most of the time the turn signals will blink once or twice and then stop. They seem to work a little better with more RPM but once I stop, so do they....at any rate I am really pleased with my bouncy seat... got it in Saturday..... if nothing is going to work,I might just end up sitting in the driveway bouncing to the oldies......

I think you got the wrong one wire sensor. Regular pusing 12v is the dash gauge wire. There are three. There is one with two wires, connector in a tee shape. That's the one for the carb ecu water temp signal. There is one fatter single wire for the dash gauge. If you ground that one, the gauge goes to max. If you meter the gague wire at the sensor, you see the gauge bimetal make/break the circuit. I think those two are close together. There should be one more smallest single wire sensor for the o/d. In the 87, this switch kills overdrive if the truck water gets too hot, so when cold, the sensor should be grounded. Go from battery + to sensor and test light should glow. If that sensor's wire is grounded, o/d should work even if sensor is bad. I've been calling it a sensor, but it's really a normally closed temperture limit switch.

If o/d does not work with working sensor/switch or with wire grounded, either the o/d solenoid valve on the top of the tranny is bad, or the wiring to it is bad.

Unplug and replug all the harness connectors. I think that's where the trouble is, or in the valve itself.

Question for fasteddy:

I am having the same exact problem down to the signals blinking slow or staying on. I have a 91 Montero LS. My sensor wiring is not quite the same as yours, but I am hoping you can be of some guidance anyhow. When you spoke of the switch/sensor to be grounded, I found two likely suspects. One is the Thermo Switch, the other the Engine Coolant Temp Gauge Unit. Both are small, both have a single wire coming from them. Could you tell me which one you were speaking of? I don't want to ground the wrong think and fry something. <img src="/forums/images/graemlins/confused.gif" alt="" />

New to all this

Aaron

"the wrong think?" Aren't I the smart one? I got called out to work last night at 12:15am, so I had no sleep when writing this. I reread your post and to clarify what I said earlier, I think you mean the thermo switch, but I want to be sure that if I ground that it will not affect my fan running to cool the engine. I don't know much about these, the last car I did all my own work on was a 71 VW fastback.... slightly more techology on this one.... <img src="/forums/images/graemlins/lol.gif" alt="" />

If you ground the gauge wire, the gauge will go to full hot. Unground that one and ground the other one and try for od engagement on the road.

Tested with an ohmeter, the tranny temp switch should have continuity from terminal to ground, and the sender tested between wiring harness connector and ground with a test light should show a flashing light, and gauge should move.

tranny temp switch is the highest and furthest aft, I think. Coolant temp sensor is further forward and lower.

Good INFO, I am having the same problem. Tranny worked fine ...changed out the fluid/filter now no O/D. I'll be checking the stuff mentioned above.
Thanks,
Terry <img src="/forums/images/graemlins/cheers.gif" alt="" />