GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Chevy K Silverado - 4WD 🢒 Bulletins 🢒 Transmission 1-2 Shift Shudder, Vibration, Slips, Chuggle (Install Generator Voltage Sense Circuit)

Transmission 1-2 Shift Shudder, Vibration, Slips, Chuggle (Install Generator Voltage Sense Circuit)

Subject:Transmission 1-2 Shift Shudder, Vibration, Slips, Chuggle (Install Generator Voltage Sense Circuit)

Models:2001-2003 Chevrolet Silverado
2001-2003 GMC Sierra
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to August 5, 2003 at Oshawa (Plant Code 1) and Pontiac (Plant Code E) or Prior to August 12, 2003 at Fort Wayne (Plant Code Z)
 
Vehicles built AFTER the dates listed above will have a Voltage Sense Circuit internal to the generator. These vehicles will NOT have a wire in terminal D of the generator connector.


This bulletin is being revised to accommodate for a 2003 model year mid-cycle enhancement. Please discard Corporate Bulletin Number 02-07-30-030 (Section 07 -- Transmission/Transaxle).

Condition

Some customers may comment that the transmission slips, a shudder, chuggle, or vibration is felt when the transmission shifts from first to second gear.

Cause

A 12 Hz electrical feedback from the charging circuit may be affecting the transmission pressure control solenoid, causing a fluctuation of the line pressure within the transmission.

Diagnostic Tip

Road test the vehicle under the following conditions:

    • Throttle position is less than 15 percent.
    • Engine coolant and transmission fluid are at full operating temperature.
    • The outside ambient temperature is warmer than 24°C (75°F).

If the condition is present, disconnect the generator 4 cavity connector (2 wires in the connector) and retest.

If the condition is no longer present, perform the correction listed below.

If the condition remains unchanged, the condition will not be corrected with this procedure. Look for other causes of the condition.

Correction

Install an external sense lead to the generator assembly. This is accomplished by adding a wire from the generator four wire connector to the generator output BAT terminal.

  1. Disconnect the negative battery cable from the battery/batteries.
  2. Slide the protective boot on the generator BAT terminal aside and remove the retainer and wire cable from the BAT terminal.
  3. Unplug the generator 4-cavity terminal from the top of the generator.
  4. Inspect cavity D on the generator connector for a red cavity plug.
    5. • If a red cavity plug is present, it is not necessary to replace the generator connector. Remove the CPA and save. Remove the red cavity plug and continue with step 9.
    • If a red cavity plug is NOT present, continue with the next step.
  5. Remove and save the orange weatherpack seal and CPA from the 4-way connector.
  6. Using the proper terminal removal tool, remove the two or three wires from the 4-way connector.
    7. • On vehicles without Supplemental Brake Assist (SBA), install a red cavity plug, P/N 12059168, into cavity "A" of the new 4-way connector, P/N 12186568.
    • On some 2003 model year vehicles with SBA, install the dark blue (Circuit 5668) wire of the vehicle wiring harness into cavity "A" of the new 4-way connector.
  7. Install the brown (Circuit 25) wire of the vehicle wiring harness into cavity "B" of the new 4-way connector.
  8. Install the gray (Circuit 23) wire of the vehicle wiring harness into cavity "C" of the new 4-way connector.
  9. Obtain a piece of 0.80 mm/18GA black wire, 254 mm (8 in) long.
  10. Install a red terminal seal, P/N 12048086, and terminal, P/N 12048074, (crimp and solder) on one end of the new black wire.
  11. Install the new black wire into cavity "D" of the new 4-way connector.
  12. Reinstall the connector seal and CPA, from the original connector, to the new connector.
  13. Plug the 4-way connector into the generator.
  14. Route the black wire to the generator BAT terminal, sliding the wire into the small end to the output terminal boot, along side the generator output wire.
  15. Crimp and solder the ring terminal, P/N 12103514, on the open end of the new black wire.
  16. Place the generator output wire and the new black wire onto the generator BAT terminal and install the retainer.

    17. Tighten
    Tighten to the BAT terminal retainer to 9 N·m (80 lb in).

  17. Connect the negative battery cable.

    18. Tighten
    Tighten the battery cable retainer to 17 N·m (13 lb ft).

Parts Information

Part Number

Description

Quantity needed for this repair

SPO Dealer Cost

J 38125

Kit Tray Location

Available from Kent Moore (approximately $12.50 per pkg)

12048074*

Terminal

1

$0.57

Tray # 2

50 per package

12059168*

Cavity Plug

1

$2.00

Tray # 3

25 per package

12048086*

Wire Seal, Red

1

$2.05

Tray # 3

25 per package

12103514*

Ring Terminal

1

$1.50

Tray # 19

N/A

12186568

Connector

1

$1.30

Must be ordered from Parts.

N/A

Part numbers shown above which have an (*) are found in the terminal repair kit, J 38125. They may be ordered either from GMSPO or SPX Kent Moore.

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

*N8505

Rewire Generator, 1-2 shudder

0.7 hr

*This is a unique labor operation number for use only with this bulletin. This number will not be published in the Labor Time Guide.