How do I know if the overdrive is working correctly? I have a 1992 245 170,000 -- The button on the shifter does nothing....or at least I think it does not do anything?

When I am driving it and I am going up a hill and if I push the car hard..the overdrive does kick in.
Is there something I should check?

thanks -

With a manual transmission, you drive your 4-speed + OD transmission like a 5-speed, except that instead of moving the shifter between the 4th and 5th gear positions, you press the button. A green light in the dash will tell you that you are in "5th" (4th with overdrive on).

With an automatic transmission, the overdrive is treated as a 4th gear on top of the other 3 speeds. Pressing the button changes from normal ("4th" (3rd with overdrive) can be used) and overdrive locked out (which will only allow shifting up the 3rd with no overdrive). If the overdrive is locked out, a yellow light in the dash will light up. You can test it by accelerating to freeway speed and feeling how many upshifts the transmission makes.

But would a 1992 car have a transmission with a separate overdrive unit, as opposed to a true 5-speed manual or 4-speed automatic? In a true 4-speed automatic, an overdrive button would simply allow or disallow the transmission to use the 4th gear.

AT or MT? This would help some of use out.

Sincerely,
--
Julio Meza

1979 264GL B27F 122K

Features Added:

BW55 To M46, Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

+Cruise Control

automatic transmission

thanks

Read this post regarding on how the OD on the AT work. This should help shed a bit of light on the subject. Other than that I would use a volt meter and a wiring diagram to figure out where the problem lies. Usually the problem is either in the OD Relay (White relay to the left of the glovebox once removed) or the actual wiring itself. You could take out the relay and resolder it to make sure all the contact points are good so the current flows just fine. You could look under the shifter cover to see if any of the wiring is frayed or cut, also under the car above the tranny and at the OD solenoid on the drivers side to see if any of the wiring has gone bad. To rule out the OD Solenoid supply 12V from the battery/hot wire from fuse box and listen for the CLICK. If it clicks it works and move on to the wiring, relay, or button. If it does not click then thats when the post below would come in handy. Also check your kick-down cable to make sure it is not binding. This would make the tranny wait until the RPM's are high before going into the next gear so I do not think this is the direct problem for your OD situation but it is a good place to check. Good Luck!

http://www.brickboard.com/RWD/index.htm?id=737805

Sincerely,
--
Julio Meza

1979 264GL B27F 122K

Features Added:

BW55 To M46, Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

+Cruise Control