BENDIX TCH-003-031 Fascicule
Technical
Bulletin
Bulletin No: PRO-03-31
Effective Date: 10/1/90
Cancels: NA
Page: 1 of 2
Subject:
TP-2 TRACTOR PROTECTION VALVE OBSOLESCENCE AND
CHANGEOVER
Effective immediately, the TP-2 Tractor Protection valve will no longer be available for service replacement,
either as new or remanufactured exchange. Because of this obsolescence, when replacement of the TP-2 is
required it will be necessary to change over to a currently produced valve. Mark catalog page 03-M-1.
either as new or remanufactured exchange. Because of this obsolescence, when replacement of the TP-2 is
required it will be necessary to change over to a currently produced valve. Mark catalog page 03-M-1.
BACKGROUND
The TP-2 is the oldest of the tractor protection valves offered by Bendix and has been in production for well over
30 years. Unlike the TP-3, 4 & 5, all of the control functions required of the tractor protection system are
contained within the TP-2 valve itself. Because of this, the TP-2 does not require the use of a specific dash control
as do the more current tractor protection valves. A variety of dash controls can and have been used with the TP-2.
The TP-2 requires three separate air connections to the tractor air system and they are; the control, tractor service,
and tractor emergency. Because of the three air connections it requires, the TP-2 is often referred to as a “three
line” system. Current tractor protection valves and systems split the line closure and automatic functions between
the dash control and the tractor protection valve and thereby eliminate the need for the third line. The PP-7 must
be used with these newer tractor protection valves.
The TP-2 is the oldest of the tractor protection valves offered by Bendix and has been in production for well over
30 years. Unlike the TP-3, 4 & 5, all of the control functions required of the tractor protection system are
contained within the TP-2 valve itself. Because of this, the TP-2 does not require the use of a specific dash control
as do the more current tractor protection valves. A variety of dash controls can and have been used with the TP-2.
The TP-2 requires three separate air connections to the tractor air system and they are; the control, tractor service,
and tractor emergency. Because of the three air connections it requires, the TP-2 is often referred to as a “three
line” system. Current tractor protection valves and systems split the line closure and automatic functions between
the dash control and the tractor protection valve and thereby eliminate the need for the third line. The PP-7 must
be used with these newer tractor protection valves.
CHANGEOVER
Because of the functions contained in the TP-2, it will be necessary in most cases to replace both the TP-2 and its
dash control. The changeover to a TP-3 and PP-7 is the most universally correct and most easily accomplished.
TP-2 valves installed on both pre and post FMVSS 121 vehicles (pre-1975 & post 1975) can be replaced using the
TP-3 and PP-7 combination with a moderate amount of re-piping. It should be noted that by following the
changeover instructions presented, the resulting tractor protection system will be brought up to FMVSS 121
standards with respect to the interlocking of tractor parking and tractor protection.
Because of the functions contained in the TP-2, it will be necessary in most cases to replace both the TP-2 and its
dash control. The changeover to a TP-3 and PP-7 is the most universally correct and most easily accomplished.
TP-2 valves installed on both pre and post FMVSS 121 vehicles (pre-1975 & post 1975) can be replaced using the
TP-3 and PP-7 combination with a moderate amount of re-piping. It should be noted that by following the
changeover instructions presented, the resulting tractor protection system will be brought up to FMVSS 121
standards with respect to the interlocking of tractor parking and tractor protection.