Product Support Program For Reworking The Disc Brake Modules On Certain D11N Tractors Caterpillar

Product Support Program For Reworking The Disc Brake Modules On Certain D11N Tractors

Usage:

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Caterpillar: Confidential Yellow

NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

NOTE: This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS8064" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

Termination Date

August 31, 1994

Problem

The brake modules may exhibit braking and/or steering actions that are too aggressive in some applications on certain D11N Tractors.

Affected Product
Model & Identification Number

D11N 74Z1-1031

NOTE: This Program applies to machines with identification number 74Z1-456 only if the machine has been converted to a ten-disc brake module.

Parts Needed

4 8E8854 Spacer

10 7G3046 Shim

10 7G3177 Shim

4 6I9417 Plug Assembly

2 6I9522 Spring (orange-109.4mm free length)

4 6L8598 Ring

10 3T6822 Shim

2 7T1112 Spring (105.4mm free length)

2 7T1113 Spring (122.9mm free length)

2 7T8568 Spring (red-62.2mm free length)

4 9W5605 Retainer

2 6Y6562 Spring (light blue-58.5mm free length)

2 6Y6564 Lever

Action Required

See attached rework procedure.

Service Claim Allowances

NOTE: This is a 6-hour job.

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Attach.

(1-Rework Procedure)

Rework Procedure

Reworking the machine following these procedures will provide a valve with new cam levers and springs to ensure adequate "dead band" between the "clutch-release/brake-applied position". Also, an external valve pressure adjustment is provided along with instructions for adjustment.

NOTE: Rework D11N Tractors with a serial number of 74Z1-456 only if they have been previously converted to a ten-disc type.

1. Remove the four 3P3202 Plunger Springs (Illustration 1, Item 6) and discard them. Disassemble and assemble the plunger springs through the end of the valve with the ten- bolt cover.

2. Replace the two 7T4623 Cam Levers with two 6Y6564 Cam Levers. Drive out the two cup plugs on top of the valve and remove bolts and washers on top of levers; the shafts can then be pulled out of side of valve. Transfer parts from the existing levers (rollers, pin, and snap rings) to the new levers. Be sure the new levers are installed in the same orientation as the existing levers. Refer to Illustration 2.

3. Remove plugs, shims, and all pressure control springs from the valve body (Illustration 1, Items 1, 3, and 4). Discard the springs since they will be replaced with new ones. Remove the spool assemblies from the valve body noting the bore from which they are removed.

4. Remove the 7T1118 Modulation Spring, shims, retainer, and snap ring (Illustration 1, Items 5, 7, 10, and 11) from the clutch spools (bores #1 and #4). Discard the spring and retainer. Before assembling a new 6Y6562 Spring to the spool, adjust the free-stack-height of the spring plus shims to 63.50 ± .13 mm (2.500 ± .005 in)(measure free-stack-height with a vernier caliper.) Assemble the 6Y6562 Spring and shims to the clutch spools with a 9W5605 Retainer and 6L8598 Snap Ring. See Illustration 3.

NOTE: After assembly, check to be sure the spring is .13mm (.005 in) loose axially. See Illustration 3.

5. Remove and discard the existing 7T8568 Modulation Spring, shims, retainer, and snap ring (Illustration 1, Items 8, 9, 10, and 11) from the brake spools (bores #2 and 3). Before assembling a new 7T8568 Spring to the brake spool, the free stack height of the spring plus shims must be 63.50 ± .13mm (2.500 ± .005 in)(measure overall length with a vernier caliper). Assemble the 7T8568 Spring and shims to the spools with a 9W5605 Retainer and 6L8598 Snap Ring. See Illustration 3.

NOTE: After assembly, check to be sure the spring is .13mm (.005 in) loose axially. See Illustration 3.

6. Install the spools into the valve body. the clutch spools (valve bores #1 and #4) can be identified by having only one set of slant lands on the spool. The brake spools (valve bores #2 and #3) can be identified by having two sets of slant lands on the spool. See Illustration 3.

7. Assemble new pressure control springs into the valve body. the clutch bores (bores #1 and #4) take 6I9522 Springs (orange stripe on spring, see Illustration 1, Item 1). The brake bores (bores #2 and #3) take 7T1112 and 7T1113 springs (see Illustration 1, Items 2 and 12).

NOTE: The shims and o-ring plug can be directly replaced with one 8E8854 Spacer and 6I9417 Plug Assembly (Illustration 1, Items 3, 4).

8. Install the spring detent blocks into the valve. See Illustration 2. Follow the adjustment procedure carefully.

NOTE: After the adjustment bolt (Item 6) has been tightened, the roller (Item 2) should be in contact with, but not depressing the clutch plungers (Item 1).

9. At high idle and warm oil, adjust brake control pressure (bores #2 and #3 to 360 ± 25 psi). Adjust the clutch control pressure (bores #1 and #4) to 335 ± 15 psi.

NOTE: If the specified control pressures cannot be attained,remove .50 mm (.020 in) of shims from the modulation spring end of the spool (Illustration 1, Item 5 or 9) and readjust the control pressure.

10. After the control pressures have been adjusted, check clutch and brake pressures at the two following control lever positions.

a. When the levers are pulled back to the "bump", the clutch pressure should be zero psi and the brake pressure greater than 300 psi.

NOTE: The "bump" is the control lever position when the levers are pulled back about half-way back and you feel a higher lever force.

b. When levers are pulled all the way back, the clutch pressure should be zero psi and the brake pressure 90 ± 10 psi.

Steering And Brake Control Valve

Illustration 1