Article 99 - Delayed or Erratic Shifts

TSB #9 - January 14, 1972
(1971-72 F, B, C, and LN 600-750 and C 800 Trucks with Allison AT-540 Automatic Transmission)


Delayed or erratic shifting of Allison AT-540 Automatic Transmissions on the subject trucks, is corrected by using one of the appropriate procedures set forth in this article. There are two different groups of transmissions and the service procedure is different for each. Each of the transmission groups are identified by serial number and have separate instructions and parts requirements.

Transmissions with serial numbers falling in Group A may require removal of the governor oil tube screen which is located in the end of the governor feed tube and installation of a larger screen which slips into the valve body governor port before the governor feed tube is installed in the valve body. Group B transmissions may require the above plus a new valve body assembly and governor assembly.

NOTE: Record the Transmission Serial Number on the Repair Order. The serial number is stamped on the transmission name plate which is located on the right hand side of the transmission case at the lower rear corner.

A. Group A Transmissions
1. Transmission Serial Numbers Affected
    All ATC 540 units with serial numbers from 3971 through and including 6291 PLUS the following (But NONE with"V" or "W" stamped in lower left hand corner of transmission name plate):
    1286 1556 1896 2417 3385
    1343 1581 1936 2439 3413
    1369 1584 1947 2444 3619
    1387 1876 1957 2517 3701
    1397 1877 2388 2526
    1540 1880 2409 3371

2. Group A Parts Required
PART NO.QTY.PART NAMECLASS
D2TZ-7E242-A1Screen, governor tubeCT
D2TZ-7B391-A1Gasket, governor coverCT
353351-S1Ball, governor pressure checkBS
D2TZ-7A191-A1Gasket, Oil panBT
D2TZ-7B122-B1Seal, modulator to trans, caseCT
D2TZ-7B122-A1Seal, oil filter intake pipe "O" ringCT

NOTE: A spare governor pressure check ball is included because original ball may be lost during removal of valve body.

3. Group A Procedure (in vehicle)
    (a) Drain oil from transmission (loosen oil fill tube connection on pan to drain oil). After oil has drained, remove oil fill pipe from oil pan. Discard the oil. Thoroughly clean the transmission oil pan.
    (b) Remove vacuum hose, vacuum modulator, modulator to case retainer and modulator actuator rod from transmission. Remove and discard the seal on modulator.
    NOTE: Inspect modulator and modulator actuator rod for nicks, burrs, dents or other damage. If present, replace part.
    (c) Remove transmission oil pan and gasket from transmission. Discard gasket.
    (d) Remove transmission oil filter and oil filter intake tube from the transmission. Remove and discard the "O" ring seal on intake tube.
    (e) Remove range control valve body assembly and three tubes. Refer to Fig. 6. (1st-rev. oil tube not illustrated).
    CAUTION: A 1/4" diameter governor pressure check ball (Fig. 7) is free to roll or fall out of transmission —be sure to observe its presence. Range selector valve is free to slide out of valve body — be sure to retain during removal of valve body.
    NOTE: Only one (1) governor check ball is required in the transmission. The new ball under "Parts Required" is listed so that a new one is available should the original ball be lost during removal of valve body or found damaged.
    (f) Remove and discard the governor screen from the end of governor feed tube as instructed in (Fig. 6).
    (g) Remove transmission governor assembly cover gasket and governor assembly from the transmission. Rotate the governor assembly clockwise to disengage from drive gear during removal. Discard the governor cover gasket.
    (h) Prior to cleaning governor assembly check and inspect for free movement of governor weights. Clean and flush governor assembly thoroughly with solvent. Recheck governor for free movement of governor weights.
    (i) Install new governor cover gasket onto transmission using an oil soluble grease to retain it in position.
    (j) Install governor oil assembly by pushing it inward with a slight rotation counter-clockwise.
    (k) Install governor cover and secure it with four 5/16-18 x 9/16 inch bolts. Torque bolts 15 to 20 ft. lb.
    (I) Install new governor oil screen D2TZ-7E242-A, closed and first, into range control valve body assembly at the location indicated in Fig. 6, then install governor feed tube. Install the remaining two (2) pressure tubes (1st-rev. tube not illustrated in Fig. 6) into control body assembly.
    (m) Locate and position governor check ball 353351-S at the oil port as illustrated in Fig. 7, it will be properly located when the control body assembly is installed.
    NOTE: Apply a small amount of petroleum jelly on governor ball to retain it at this location during installation of control body assembly.
    (n) Install range control valve body assembly including the oil tubes (3) and governor check ball as an assembly onto the transmission.
    NOTE: For ease of control body assembly installation, use two (2) 1/4-20 x 3-1/2 inch bolts to guide, hold body assembly weight, align and index oil tubes, shift selector components and to maintain governor ball and selector valve in location during installation. Be sure guide bolts are replaced with the standard mounting bolts as related in next step (o).
    (o) Secure the control valve body assembly with nineteen (19) bolts in the following manner.
      (1) Install the detent roller and spring assembly with its roller centered exactly over the selector lever detent and its rear tab in the hole immediately behind the bolt hole. Install a 1/4-20 x 1-3/4 inch control body mounting bolt through the spring and valve body into transmission case. Be sure spring roller is centered laterally on the selector lever detent.
      (2) Install a 1/4-20 x 2-3/4 inch bolt near the center of the valve body.
      (3) Install the remaining seventeen (17) 1/4-20 x 2-1/4 inch mounting bolts.
      NOTE: Replace the two (2) guide bolts used for installation of body assembly with two of these 2-1/1- inch bolts.
      (4) Torque the nineteen bolts evenly to 8 to 12 ft; lb.
      CAUTION: Do not overtorque the mounting bolts. Be sure the detent spring roller is still aligned over the selector lever detent after the 1-3/4 inch bolt is final torqued.
    (p) Install new "0" ring onto the straighter end ill filter intake pipe and install pipe, end first, into transmission.
    CAUTION: Be sure pipe is rotated to a position whereby full movement of the selector lever does not contact the side of intake pipe.
    (q) Install transmission oil filter and secure with one (1) 5/16-18 x 5/8 inch washer head screw. Torque screw 10 to 15 ft. lb.
    CAUTION: Again check for full movement of selector lever to be sure it does not contact the side of filter intake tube.
    (r) Be sure transmission oil pan has been thoroughly cleaned. Install oil pan and new pan gasket onto transmission. Secure the oil pan with twenty-one (21) 5/16-18 x 5/8 inch washer head screws. Torque the screws evenly to 10 to 13 ft. lb.
    (s) Install vacuum modulator actuator rod, larger end first, into transmission.
    (t) Install new seal ring onto the vacuum modulator and install modulator into transmission. Rotate modulator until hose nipple faces toward the front of transmission at an angle of 10° below horizontal.
    (u) Install modulator retainer with the bent tabs toward transmission, and secure it with a 5/16-18 x 3/4 inch bolt. Torque the bolt 15 to 20 ft. lb.
    (v) Install vehicle vacuum hose to the transmission vacuum modulator.
    CAUTION: Check hose for splits, kinks, obstructions or general deterioration. Replace if necessary.
    (w) Install and secure transmission oil fill tube to transmission oil pan.
    (x) Connect vehicle range control linkage to the transmission.
    NOTE: Check all range linkage from vehicle cab area to transmission for proper adjustment and that it is in good repair. Be sure proper range indication is present at the shift toiler and that the vehicle neutral start switch adjustment is correct — that is, the vehicle can be started only when the ignition switch is "on" and the selector lever in vehicle cab is in the "neutral" range position.
    (y) Refill transmission with the approved fresh automatic transmission fluid using a clean oil fill container.
    NOTE: Pour approximately 10 quarts of oil initially into the transmission. After vehicle is started and normal operating oil temperature (150° to 200°F., sump) is reached, the oil level should be checked prior to road testing.
    (z) Prior to actual road testing, check for oil leaks and proper oil level after vehicle has been operated enough to warm up engine and transmission, to be sure sufficient oil is in transmission.
    CAUTION: Do not overfill with transmission oil. The oil level rises 0.5 to 0.6 inch as sump temperature increases from 75-80°F. to 180°F. It is important not to fill above the "ADD" mark (approximately 10 quarts) on the dipstick before the transmission has run enough to reach operating temperature. One quart of oil raises the oil level approximately 0.55 inch.

4. Special Instructions - Group A
After completing the corrective action, stamp the letter "W" on the transmission name plate in the in the lower left corner as close as possible to the "are" on the left and down to the bottom line of the "Serial No."

B. Group B Transmissions
1. Transmission Serial Numbers Affected
    The transmissions in this group include all those with serial numbers BEFORE (but not including) 3971 EXCEPT the following (but NONE with "V" stamped in the lower left corner of transmission name plate):
    1286 1556 1896 2417 3385
    1343 1581 1936 2439 3413
    1369 1584 1947 2444 3619
    1387 1876 1957 2517 3701
    1397 1877 2388 2526
    1540 1880 2409 3371

2. Group B Parts Required
PART NO.QTY.PART NAMECLASS
D2TZ-7E242-A1Screen, governor tubeCT
D2TZ-7B391-A1Gasket, governor coverCT
353351-S1Ball, governor pressure checkBS
D2TZ-7A191-A1Gasket, Oil panBT
D2TZ-7B122-B1Seal, modulator to trans, caseCT
D2TZ-7B122-A1Seal, oil filter intake pipe "O" ringCT
D2TZ-7A100-A1Kit, control body and governor assemblies for transmissionB
NOTE: A spare governor pressure check ball is included because original ball may be lost during removal of valve body.

3. Group B Procedure (in vehicle)
    (a) Perform steps (a) thru (e) as described in Group A EXCEPT discard the range control valve body assembly.
    (b) Remove governor screen from the end of the governor feed tube or governor screen from the port in the valve body and discard screen.
    (c) Perform step (g) from Group A Procedure EXCEPT discard the governor assembly.
    (d) Omit step (h) and perform steps (i) thru (z) using the new range control valve body and governor assemblies.

4. Special Instructions - Group B
After completing the corrective action, stamp the letter "V" on the transmission name plate in the lower left corner as close as possible to the "are" on the left and down to the bottom line of the "Serial No." block.

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Figure 6
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Figure 7


PRODUCTION CORRECTION: 9/2/71
WARRANTY STATUS:
Reimbursable within the provisions of the Warranty and Policy Manual.
OPERATION NO: SP-7-7131-A-71
TIME: 2.3 hrs.
DLR. CODING: Basic Part No. 77131 - Code 49