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

will cause the various hydraulic actuators to engage faster. This will feel like a sudden and rough engagement. On the one hand, with fast
engagement, there is little chance for the clutches and brakes to slip. This means less wear, and hence a longer lasting tranny. On the
other hand, these fast engagements result in a bit of jarring to the occupants of the car. The solution is to have the valve body serviced.
This can usually be done without removing the tranny. So you have to decide. Can you live with a little jarring, or do you want to spend
some money and see if it can be smoothed out.
Overdrive Relay and Function:
Overdrive Operation. [Roger Scott] The "overdrive" electrical circuit works works like this -- the A-70/1 automatic transmission is a 4-speed
transmission, but, unless the "overdrive" solenoid is energized, it is by default a 3-speed automatic transmission. When you hit the
"overdrive" button what really happens is you de-energize the solenoid, disabling 4th gear; you get a downshift to 3rd gear and the "uparrow"
light on the instrument panel.
Basic Diagnostics. [Roger Scott]
● Check fuse 12: intact, ends are clean and it fits tightly.
● Check for fraying or severing of the wires to the solenoid - under the car on the left side of the transmission. Pay particular attention
to the metal retaining clamp near the front end of the shift lever where the wires pass through.
● Make sure the wires to the switch on the shifter head are in good order. You can remove the relay and test for continuity between
terminals 1 (15 on the relay) and 4 (86 on the relay) which are the switch wire terminals.
● You can test the relay and solenoid by jumpering with a spade-terminal jumper wire. Pull the relay, jumper between terminals 1 (15
on the relay, or +12V) and 3 (87 on the relay, or the solenoid). This bypasses the relay and energizes the solenoid directly. Or run
+12V directly to the solenoid through a long jumper wire from the battery.
● [Don Foster] All this having been noted, 90%+ of overdrive failures result from relay solder cracks. See below for instructions for
relay repair.
Relay Problems and Repair:
[See Relay Locations for a detailed picture of relay location and removal instructions.] [Symptom:]I have a friend with a '90 740 automatic
and he is having intermittent OD problems that seem to be weather related. It won't go into OD when the weather is
cold. Is the relay on the relay tray? If so, which one is it? [Diagnosis:] Yes it does sound like an OD relay. If I remember
correctly on 740 it is by the Ashtray/FuseBox. It is pretty common component failure on the bricks. It will be a white Overdrive Relay
Hella relay. Pretty simple to change. The relay is about $40-43 through Mail order from dealership. In my case I was
"sure" it was the wiring, switch or solenoid, as the relay "looked" just fine. But as soon as I replaced the relay, all