Looking for the gearbox cutoff switch on a 240 year 1985 drives ok but wont get out of 4th gear, looked everywhere on car but cannot find the damn thing!

 

You won't be able to find a replacement one. Obsolete most likely.


OD problems are easy to fix if you know how to diag circuits with a multimeter. Or just go lo tech and look for frayed wires in the tranny tunnel and repair.

 

gearbox cut off switch? not sure what you're referring to.

is this an automatic or stickshift/manual transmission?

the automatics have an electric enabled 4th gear overdrive. pushbutton on the stickshift toggles a relay behind the dash... the relay output is ON to enable OD/4th, and OFF to disable it. the yellow up-arrow light is lit when the OD is OFF. and not lit when the OD is enabled. The actual OD is controlled by a solenoid valve on the side of the transmission, this solenoid is powered ON when the OD is enabled, and powered OFF to disable OD (so, light ON == OD solenoid OFF, confusing, eh?).

if the light isn't toggling when you push the button, it could be either the wiring to the button inside the shifter lever, or the OD relay behind the dash. if the light IS toggling, but the OD is never enabled, such that you get max 3 gears, then it might be the wiring at the tranny that REVOLV refers to, or the solenoid itself, or the transmission innards.

 

When I was a rookie I had more than one RWD Volvo with OD issues. I dug deep into circuit diag and taught myself how to do it. I personally loathe the Volvo OD stuff. They put an OD on the back of the manual tranny and hacked it in there. Auto tranny: the wires fail commonly. The solenoid poops less commonly. 8/10 it's a wiring issue.

I went with the other backdooor method. The M47. 5th gear is bolted to the back of the trans and it works WAAAAY better than the electromechanical baloney Volvo engineered. Well, it works well when the wires arent frayed from heat and oil after decades.

These RWD bricks still last longer than the overengineered modern cars.

 

those manual OD's were right out of a brit car from the 60s, same Laycock Type J OD as our TR-6 had. on the TR6, it was controlled by a steering wheel stalk, up for OD, down for normal, and this stalk switch directly controlled the OD solenoid... needless to say, that switch, being Lucas, was subject to frying itself, so ours was modded by the previous owner with a Bosch relay, switch turns on relay, relay turns on OD, all worked much better.