PSP FOR IMPROVING TRAVEL MODULATION, JERKY STEERING, AND/OR TRAVEL DRIFT PROBLEMS ON CERTAIN 235C EXCAVATORS - PS0468 - MAI LED US AND CANADA, COSA Caterpillar

U-134
O-104
4005   PS0468
NOTE: This Program can only be administered after a failure
(complaint) occurs. The decision whether to apply the Program is
made by the dealer. When reporting the repair, use "PS0468" as
Part Number, "7755" as Group Number, and "96" as Description
Code.

July 31, 1991

Certain 235C Excavators may experience one or more of the following problems:
.....Poor travel modulation
.....Jerky steering
.....Excessive travel drift
This program resolves these problems with changes to throttling slots of
thetravel stems and overspeed stems plus brake release timing changes on
certain
machines.

Model Identification Number
235C 5AF1-887, 889, 892, 893, 895, 897-899
2PG1-586
3WG1-117, 119-195
4DG1-446

1. Track Stem Changes - All Machines
2 total as applicable:
6E2215 Stem
6E2216 Stem
6E2217 Stem
Track Overspeed Stem Changes - ALL Machines
4 total as applicable:
6E2332 Stem
6E2333 Stem
6E2841 Stem
2. Brake Release Timing Changes for 5AF1-829 Plus Following PINs (2PG1-557,
3WG1-179, 4DG1-430) ONLY If Equipped with Increased Lift Attachment
1 - 4E0737 Tube A. 1 - 5P4272 Union
1 - 4E0738 Tube A. 1 - 9S4191 Plug
6 - 3J1907 Seal 1 - 307942 Elbow
1 - 8J6875 Valve A. 1 - 307947 Elbow
2 - 6M6853 Tee

Use the attached procedure to install:
.....track stems with improved throttling slots
.....overspeed stems with improved throttling slots
.....brake release timing changes (resolver valve)

Product Caterpillar Dealer Suggested Customer Suggested
smu Parts Labor Hrs. Parts Labor Hrs. Parts Labor Hrs.
(D/N) (Cost)  (C/L) (Sell)
***** Stems Only *****
0-3000 100% 4 0 2 0 0
3001-5000 33 1/3% 2 0 2 50% 2
***** Stems & Brake Release *****
0-3000 100% 6 0 2 0 0
3001-5000 33 1/3% 4 0 2 50% 2
NOTE: This is a 2-hour job for installing new stems and a 4-hour job to
bleed air, adjust system, etc. It is an additional 2-hour job
for the brake release timing changes, If the problem has been
documented for a particular PIN and reported via SIMS (or other
documented correspondence) to Caterpillar, the SMU when the
problem was documented will apply.

Any parts removed (with the exception of cores used for Caterpillar
Remanufactured parts) can be rendered useless and scrapped immediately upon
completion of the repair.
Attach. (1-Rework Procedure)
Rework Procedure
TRACK STEMS (2) AND OVERSPEED STEMS (4)
1. Remove end cap housing with seal for a track spool.
2. Remove track stem.
3. Remove housing with seal for one overspeed stem in same valve body.
4. Remove overspeed stem. A longer cover bolt (7X0316 or 7F8698) may be
used to remove tension from the spring for the overspeed stem.
5. Measure diameter of overspeed stem removed. Make two measurements 90
deg. apart.
6. Select a new stem. New stem diameters are:
6E2332 = 31.653 +/- 0.002 mm (1.2462 +/- 0.0001")
6E2333 = 31.689 +/- 0.002 mm (1.2476 +/- 0.0001")
6E2841 = 31.725 +/- 0.002 mm (1.2490 +/- 0.0001")
Because there can be differences in results from using different
measuring equipment, it is necessary to measure the diameter of a new
stem and compare it with the diameter of the old stem. The diameter of
the new stem selected can be + 0.010 mm (0.0004") - 0.026 mm (0.0010")
the diameter of the old stem.
7. Install the new overspeed stem. Install housing with seal for overspeed
stem.
8. Repeat Steps 3 through 7 for other overspeed stem in same valve body.
9. Measure diameter of track stem removed.
a. Measure and record diameter of three different lands.
b. Make two measurements per land, 90 deg. apart.
10. Select a new stem. New stem diameters are:
6E2217 = 38.037 +/- 0.002 mm (1.4975 +/- 0.0001")
6E2215 = 38.057 +/- 0.002 mm (1.4983 +/- 0.0001")
6E2216 = 38.077 +/- 0.002 mm (1.4991 +/- 0.0001")
Measure the diameter of a new stem and compare it with the diameter of
the old stem. The diameter of the new stem selected can be + 0.002 mm
(0.0001") - 0.018 mm (0.0007") the diameter of the old stem.
NOTE: It is possible that new stems will not fit every diameter.
Contact your product analyst for assistance if none of the new
stems fit within tolerances given.
11. Install the new stem so the end with the part number is toward the
outside (left) of machine.
12. Install end cap housing with seal
13. Repeat Steps 1 through 12 for the track stem and overspeed stems in the
other valve body.
BRAKE RELEASE TIMING CHANGES
14. Remove the tube assembly (3) that connects the track brake valve to the
logic valve. This part will not be reused.
15. Install a 9S4191 Plug with 3J1907 Seal (8) in the logic valve where the
tube assembly was previously connected.
16. Install a 5P4272 Union with 3J1907 Seal (9) in the track brake valve
where the tube assembly was previously connected.
17. Install an 8J6875 (Resolver) Valve Assembly (13) on the end of the
union.
NOTE: Do not tighten fittings until all lines are connected.
18. While facing the track brake and logic valves, disconnect at the right
side of the logic valve the tube assembly (5) that connects to the speed
control valve group.
19. Remove the elbow (4) from the logic valve.
20. Install a 6M6853 Tee with 3J1907 Seal (7).
21. Install a 307947 Elbow with 3J1907 Seal (14) in the 8J6875 Valve As.
22. Install a 4E0737 Tube Assembly (6) between the elbow and tee.
23. Reconnect the tube assembly (5) that connects the speed control valve
group to the tee in the logic valve.
24. Disconnect at the left side of the logic valve the other tube (1) that
connects to the speed control valve group.
25. Remove connector (2).
26. Install a 6M6853 Tee with 3J1907 Seal (12).
27. Install a 307942 Elbow with 3J1907 Seal (10) in the 8J6875 Valve
Assembly.
28. Install a 4E0738 Tube Assembly (11) between the tee and elbow.
29. Reconnect the tube assembly (1) that connects to the speed control valve
group to the tee in the logic valve.
30. Tighten all fittings.
TRAVEL ADJUSTMENT
31. Install gauges in the valve and housings for travel stems to monitor
"partial pedal" settings. Partial pedal is defined as having control
valve pilot pressure between 970 and 1105 kPa (140 and 160 psi).
32. Move machine to a flat, level area with markings to determine travel
drift.
33. Work machine until hydraulic oil temperature is in the operating range
on the gauge.
FULL PEDAL
34. Drift at full pedal (maximum control valve pilot pressure) is caused by
a difference in flow from the pumps. This should be corrected before
adjusting for partial pedal.
PARTIAL PEDAL
35. Adjust travel pedal until travel stem pilot pressure is between 970 and
1105 kPa (140 and 160 psi).
36. Determine the amount of drift from straight line travel and adjust as
needed until drift while traveling in a forward direction (in the
direction of the front idlers) and reverse (in the direction of the
sprocket) is 3' per 100' or less.
Travel Drift* Turn Adjusting Screw No. **
Direction Direction In - or - Out
Forward Right  15 18
Forward Left 18 15
Reverse Right  16 17
Reverse Left 17 16
* Drift direction is based on forward travel.
** All adjustments should be by turning the adjusting screw inward unless
travel initiation pilot pressure is above 120 psi. If the valve is
"over-adjusted", the screw should be turned back to its previous
position and then turned in a lesser amount. If travel initiation pilot
pressure is above 120 psi, the "out" adjustment direction should be
used. Travel initiation pilot pressure should not be below 100 psi.
Turning the screw "in" increases pressure requirements and turning it
"out" decreases pressure requirements.
37. Remove gauges from valve and housings.
38. Make sure all air is bled from tank circuits.
39. Check for leaks. Correct as necessary.
Item Part
Number Number Description
1 Existing Tube Assembly
2 Existing Connector
3 Existing Tube Assembly
4 Existing Elbow
5 Existing Tube Assembly
6 4E0737 Tube Assembly
7 6M6853 Tee
3J1907 Seal
8 9S4191 Plug
3J1907 Seal
9 5P4272 Union
3J1907 Seal
10 307942 Elbow
3J1907 Seal
11 4E0738 Tube Assembly
12 6M6853 Tee
3J1907 Seal
13 8J6875 Resolver Valve Assembly
14 307947 Elbow
3J1907 Seal
****** IMAGE: SEBE4342.00001.001
CAPTION: Illustration 1 - Location Of Existing Parts
****** IMAGE: SEBE4342.00001.002
CAPTION: Illustration 2 - Location Of New Parts
****** IMAGE: SEBE4342.00001.003
CAPTION: Illustration 3 - Location Of Adjusting Screws