I Don’t Like the Cold
By
Wayne Colonna
The past winter months brought to surface a no up shift out of first gear when cold with the SAAB/Volvo 50-
42LE transmission. When it warms up all shift sequences are restored. The time varies in which this occurs.
The problem has been traced to a mechanical failure of the number 1 shift solenoid with the black connector as
seen in figure 1. Both the number 1 and number 2 shift solenoids are normally closed solenoids when off and
opens to exhaust when energized. Figure 2 provides a first gear hydraulic. Shift solenoid 1 is off and shift
solenoid 2 is on. With shift solenoid 1 off, pressure is allowed to stroke the 1-2 shift valve. When the 1-2 shift
needs to occur, this solenoid is energized. The pressure from the solenoid stroking the 1-2 shift valve is
exhausted and the valve closes by spring force. Line is then directed into the B2 circuit as seen in figure 3. And
as previously stated, in cold climate conditions, this solenoid does not open to exhaust when energized
preventing the up shift.
Since shift solenoid number 2 has not exhibited this malfunction when cold, it is the only solenoid you can
purchase for both shift solenoid 1 and 2. Everything about the two solenoids are the same except for the
direction of the connector as you can see in figure 4. There is enough length with the internal wiring harness to
use a green connector style solenoid in the shift solenoid 1 location as you can see in figures 5 and 6. The
Volvo part number for this solenoid is 6843783.
On another note, each of the shift solenoids and the TCC solenoid have a basket style filter as seen in figure 7.
The open top of the basket must face the spacer plate. If these filters are installed upside down the solenoids will
be rendered inoperative. The result of all three being upside down would be, no TCC, no 1st, no 4th and no
reverse. What a mess! ATSG has a full service technician guide available for this unit which includes a complete
set of hydraulics as well a mapping of the valve body and case circuits.
