86 740 GLE has no overdrive, it's the automatic, Mileage is unknown because the odometer stopped working at 98k miles. I've replaced the fuse, Seeing how it was blown. I also don't have reverse lights, And I checked the wiring for the the button and it seemed to be okay. What else can I check?

 

Check the relay. Dollars to doughnuts it's the relay. If not that it might be the wire to the solenoid or the solenoid. But most likely it's the relay. I dont know much about 700s but the 240 1989 has the o/d relay in the mid console under the left heater vent. I took out my glove box and could reach it that way. It should be orange or white little rectangular box. To check it, jump the proper terminals on the plug it attaches to and drive it around. If the O/D engages, then you know it's the relay.

 

Where would it be located on the transmisson? Also my fuse block is right under where the stereo and hvac controls are. Any diagrams I can look at? Thanks.

 

http://en.allexperts.com/q/Volvo-Rep...-overdrive.htm found this googling.

If you can get your hands on a haynes manual it's an invaluable resource for things like wiring diagrams. Some time ago i stumbled on a PDF showing where all the relays were in the cab, but damned if i remember where.

 

Okay, I checked the relay, Was afraid to jump it, so I got a new one. Didn't work, so I'm guessing it's the wire to the solenoid on the transmission.

 

Ugh, It's just too much BS to work on, I heard something about a bypass kit, but does that work with the 86 model 740's?

 

All you need to know: http://www.ipdusa.com/Volvo-200/Tran...-266-672-1891/

 

Question: Could I just wire like a 12v power with a switch to the solenoid to get it to work? I am getting really desperate and ordering online isn't an option

 

Most 740's have the overdrive in the rear axel. Read the owners manual and see what it says about overdrive.
http://www.volvocars.com/us/top/comm...yourvolvo.aspx

 

Rear....Axle......Over...drive...?

How does that work?

I noticed some wiring and a plug going into the pumpkin, But I thought that might've been for like traction control or something

 

If replacing the relay didn't do it, and you have checked for power at all points in the circuit, then the solenoid itself is broken. The diaphragm no longer pushes air to trigger the switch. No amount of new switches is going to help that. You can double check that the solenoid is broken. It's in the Haynes manual for the car. I don't know the process off hand. But if that's the case you either get a new solenoid, or find someone who can order online because nothing else is going to do it.

 

When the rear axle senses that you are going over a certain speed, like 45 MPH or 50 mph, it will switch the rear axle gear ratio. The owners manual should explain how it works.