Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

You can also pull the solenoid entirely, replacing it with a
metal plate, and remove the ability to use the button to
manually shift down into third. See the link below for IPD's
solution to solenoid troubles.
[E. J. Ohler] Forget about a new $150 solenoid and $50
relay: take the solenoid out, cut the wire off, grind a small
groove between the center hole and aft hole in the
solenoid face, and reinstall to allow fluid to move and
disable the solenoid as a solution to solenoid troubles.
Use a Dremel 1/8 inch grinding tool (the metal is hard so
you will use two) or a diamond bit. Clean the matching
holes in the tranny using drill bits the same diameter, but
don't drop them into the transmission. Replace the outer Oring
but not the inner where the groove passes through.
From start to finish this is a 3 hour job that saves you a lot
of headaches. You don't need the manual 4-3 downshift in
most instances anyway.
Solenoid with Ground 1/8 Inch
Groove
Solenoid Quality Reports:
Solenoid Modification for OD Troubles
[Tip from Dan Marino] My recently-installed Scantech OD solenoid failed. I discovered that the rubber
top cap (the part where the electrical wire attaches to the solenoid) had totally split away from the
metal solenoid valve parts. Basically, the top blew off of the thing. The result, massive transmission
fluid leakage. My conclusion is that this ScanTech overdrive solenoid suffers from poor quality
construction, cheap-o materials, and design flaws. The next day I was able to pull an original Volvo
overdrive solenoid from a junker for a cost of $5.25. A quick comparison showed the Volvo part to be
of superior design, more metal, and less plastic/rubber.
Overdrive Switch Replacement. [Kevin] Last summer I had the entire shifter assembly apart replacing the overdrive switch and cleaning
out 9 years worth of crud built up in the bottom of the pan. All you need to do is set the parking brake, put the transmission shifter in
neutral, and pull the handle straight up: it just 'snaps' into position. The overdrive switch is about $35 (US) from the dealer and it's just a
matter of threading the lead down thru the shaft and back up to plug in to the connector on the front right portion of the 'hump' behind the
ash tray. You'll have to remove the ash tray in order to reach it, and you may need to remove some other stuff: look to the right of the fuse
bus.