Starter Overhaul 28-MT

If the 28-MT motor does not perform to specifications, disassembly may be necessary in order to perform further testing of the components. Disassemble the starter motor only as necessary in order to perform repair or replacement of the components.

Do not attempt to disassemble the following components that are serviced as assemblies:

1. Scribe marks completely down 1 side of the starter motor in order to ensure proper alignment of all of the components during assembly. Use a colored pencil or a marker that will show on all of the components.



2. Use the following procedure in order to remove the motor lead on the frame assembly from the solenoid assembly:

2.1.	Remove the nut from the motor terminal.

2.2.	Slip off the motor lead.

2.3.	Reinstall the nut.

3. Remove 2 through-bolts.
4. Remove 2 brush plate screws.
5. Remove the commutator end frame and the O-ring seal.

Important: Do not lose the small dowel pin that is installed between the frame assembly and the gear reduction and drive group. The dowel pin is necessary for assembly. If the dowel pin is lost, replace the dowel pin with a 2 mm X 10 mm (0.79 in X 0.394 in) long pin. Obtain the new pin or manufacture the pin locally.

6. Remove the following components:

•

The frame

•

The field

•	The brush holder group

•	The dowel pin

•	The O-ring seal

•	The armature may come off with the frame, the field and the brush holder group or the gear reduction and drive group.

7. Remove the armature assembly that has the bearings.

Do not remove the bearings from the armature assembly unless replacement of the bearings is necessary. Refer to Armature Bearing Replacement.

8. Remove the solenoid screws.
9. Remove the solenoid assembly.

Pivot the inside end of the solenoid assembly out of the engagement shift lever drive group in order to withdraw the solenoid assembly.

1. Disassemble the insulated brush screws. Move the brush holder assembly with the brushes slightly away from the frame and the field assembly in order to reach across with a screwdriver and remove the screws.
2. Disassemble the frame and the field assembly.
3. Disassemble the grounded brush screws.
4. Disassemble the brushes if the brushes need replacement.
5. Use the following procedure in order to disassemble the brush springs if the brush springs need replacement:

5.1.	Grasp the brush end of each brush spring with needle nose pliers.

5.2.	Twist the spring end away from the brush. Remove the brush.

1. Disassemble the housing bolts.
2. Disassemble the armature support bracket.

Important: Washers may stick to the bracket or to the driveshaft and the clutch group as the bracket is removed. In either case, note the position and the number of each of these washers.

3. Disassemble the washers.
4. Disassemble the drive housing plug and plate. Pry out the housing plug with a large flat-bladed tool.
5. Disassemble the following components:

•	The shift lever nut

•	The washer

•

The screw

6. Disassemble the shift lever and the driveshaft and clutch group from the drive housing together. Then separate these components. Do not remove the bushing plug or the bushing from the drive housing unless replacement is necessary.

Disassembly of the driveshaft and clutch group is not required unless it is necessary to clean, inspect, or replace one or more parts of the group separately.

1. Disassemble the stop rings and the pinion stop.
2. Position the driveshaft and clutch group on a work bench with the internal gear end down.



3. Fabricate a tube approximately 22 mm wide (2). Drive the pinion stop toward the clutch drive assembly until the pinion stop clears the stop rings.
4. Pry the stop rings out of the driveshaft groove. Slide the stop rings off the end of the shaft. Do not scratch the driveshaft.
5. Inspect the edges of the shaft groove for burrs that may form through repeated cranking cycles. These burrs may make removal of the pinion stop and the clutch drive assembly difficult.
6. Slide the pinion stop off the driveshaft. Discard the old pinion stop and the stop rings. Use new components for assembly.
7. Disassemble the driveshaft support from the driveshaft. Do not remove the bearing from the driveshaft unless replacement is required.

Notice: Ball bearings that are removed from the armature must be replaced with new bearings. The removal procedure causes internal damage to the bearings.

1. Remove the armature bearings (1,3) and the armature (2) if replacing the armature and the bearings is necessary.
2. Use a suitable bearing puller in order to remove the commutator end or the drive end bearings from the armature assembly.

1. Use a tube that bears only on the bearing inner race in order to install the new commutator end and/or the drive end bearings to the armature assembly.
2. Press on the bearing until the inner race bottoms out against the shoulder of the armature shaft.
3. Install the armature and armature bearings.

Tools Required

Locally Fabricated Tool

Use the following procedure in order to remove the center support bearing from the driveshaft if the center support bearing needs replacement:

Notice: Ball bearings that are removed from the armature must be replaced with new bearings. The removal procedure causes internal damage to the bearings.

1. Inspect the center support bearing in order to determine if the center support bearing needs replacement.
2. Proceed with the following steps if the center support bearing needs replacement.



3. Fabricate a tool for removing the center support bearing using the dimensions shown.



4. Place the bolts in the fabricated tool.



5. Place the driveshaft in a suitable support fixture.



6. Place the bolt ends of the locally fabricated tool through the access holes in the wide end of the driveshaft.
7. Squarely press the bearing (1) off the surface on the center shaft.

1. Install the new bearing into the driveshaft using the locally fabricated tool that bears only on the bearing inner race.
2. Press on the bearing (1) until the inner race bottoms out against the shoulder on the driveshaft.

1. Inspect the drive end housing bushing (9) in order to verify if the drive end housing bushing needs replacement.
2. Use the following procedure in order to remove the drive end housing bushing (9) from the drive end housing (7) if the drive end housing bushing needs replacement.

2.1.	Drive out the plug, if present, from inside the drive housing.

2.2.	Use a file in order to clean away any remnants of the old stake and any metal shavings in order to prepare for installation of a new plug.

2.3.	Use a suitable tool in order to press out the bushing.

1. Use a suitable tool in order to press the new bushing into the drive housing until the bushing is flush with the inside of the housing.
2. Install a new plug, if used, in the drive housing.
3. Stake the housing material over the plug at 3 places, equally spaced.

Armature bearings and the driveshaft support bearing are permanently lubricated. Do not add lubricant to these bearings. Use GM P/N 1960954 grease lubricant or the equivalent in order to lubricate the following areas during assembly. Avoid using excessive lubrication.

If disassembled, position the driveshaft on a work surface with the internal gear end down. Assemble the driveshaft and clutch group in the following way:

Important: If the center support bearing is being replaced, install the center support bearing on the driveshaft.

1. Install the driveshaft support to the driveshaft, seating the bearing in the support.
2. Install the clutch drive assembly to the driveshaft.



3. Install the new pinion stop onto the driveshaft.

•	Slide the pinion stop onto the driveshaft until the recess for the stop rings faces up.

•	Install the stop rings into the groove in the driveshaft.

•	Pick the assembly up. Support the assembly under the pinion stop. A metal block, with a U-shaped cutout that will slide over the shaft between the pinion gear and stop, can be clamped in a vise order to provide support.

•	Ensure that the stop rings are seat fully in the pinion stop recess.

•	Stake the upper edge of the pinion stop over the stop ring at 4 equally spaced places.

•	Do not allow the staked metal to contact the driveshaft.

Important: 

•	If the drive end bushing and the plug are being replaced, install these components into the drive housing.

•	Lubricate the following components:

•	The drive end housing bushing

•	The shift lever

•	The driveshaft

1. Install the arms on the shift lever with the shift collar onto the driveshaft and clutch group.
2. Install the assembled shift lever and the driveshaft and clutch group into the drive housing.

•	Align the holes in the driveshaft support with the holes in the drive housing.

•	Ensure that the driveshaft support fully seats in the drive housing and that the driveshaft bearing remains fully seated in the driveshaft support.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

3. Install the following components:

•	The shift lever screw

•	The washer

•

The nut

Tighten
Tighten the nut to 4.5 N·m (40 lb in).

4. Install the plate, if used, and the drive housing.
5. Install the washers in the same number and position as noted at disassembly.
6. Install the armature support bracket to the drive housing. Align the mark made prior to the disassembly with the mark on the drive housing.
7. Install the drive housing.

Tighten
Tighten the drive housing bolts to 8.5 N·m (75 lb in).

1. Install the brush springs if removed.

1.1.	Start each brush spring onto the post on the brush holder assembly just enough in order to hold the inside end of spring from turning.

1.2.	Grasp the free end of the spring with needle nose pliers. Twist the spring to the right over the top of the brush socket.

1.3.	Push the spring fully onto the post. Then release the free end in order to engage the notch in the brush socket.

Notice: Brush leads may be damaged by excessive handling. Do not overflex the leads near the clip welds or the clips may break




2. Install the brushes (3), to the brush holder assembly (1) with the springs (2).

2.1.	Ensure that the insulated brushes go into the brush sockets of the brush holder assembly that mounts on the insulation.

2.2.	To install each brush, grasp the free end of the brush spring with needle nose pliers Twist the spring to the right in order to clear the brush socket. Insert the brush partly into the brush socket.

2.3.	Gradually release the springs so that the spring end contacts the side, not end, of the brush. This will hold the brushes retracted until the brush holder is installed over the armature commutator.

3. Position the terminals of the grounded brush leads behind the terminal tabs on the brush holder.
4. Install the grounded brush screws.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

5. Insert the brush screws through the terminal tabs on the brush holder. Thread the brush screws into the brush lead terminals.

Tighten
Tighten the grounded brush screws to 1.5 N·m (13 lb in).




6. Install the frame and field assembly to the brush holder assembly.

5.1.	Position the brush holder assembly (with installed brushes) over the terminal end of the frame and field assembly.

5.2.	Attach the terminals of the insulated brush leads to the conductors in the frame and field assembly with the insulated brush screws.

Tighten
Tighten the insulated brush screws to 1.5 N·m (13 lb in).

1. Support the gear reduction and drive group.
2. Place the pinion gear end down.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

3. Use the following procedure in order to install the solenoid assembly:

3.1.	Pivot the plunger of the solenoid assembly in order to engage the plunger to the shift lever in the gear reduction and drive group.

3.2.	Position the solenoid mounting flange.

3.3.	Install the solenoid mounting screws.

Tighten
Tighten the solenoid screws to 2.8 N·m (25 lb in).

4. Install the frame seal.

Important: If you are replacing the armature bearings, install the bearings onto the armature. Refer to Armature Bearing Replacement.

5. Use the following procedure in order to install the armature assembly and the bearings into the gear reduction and drive group.

5.1.	Ensure that the teeth align.

5.2.	Seat the bearing on the armature shaft fully into the housing recess.

6. Use the following procedure in order to install the frame the field and the brush holder group.

6.1.	Place the dowel pin into the hole in the armature support bracket of the gear reduction and drive group.

6.2.	Position the frame the field and the brush holder group over the armature assembly.

6.3.	Align the hole for the dowel pin.

6.4.	Align the marks made during disassembly.

6.5.	Seat the frame the field and the brush holder group into the gear reduction and drive group.

6.6.	Twist the brush springs away from the brushes.

6.7.	Slide the brushes in order to contact the commutator on the armature.

6.8.	Release the brush springs in order to contact the ends of the brushes.

6.9.	Verify that the brush spring tension is 44.5-49 N·m (10-11 lb).

6.10.

If the brush spring tension is not correct, replace the brush springs.

Important: The O-ring seal will damage easily during installation of the commutator end frame. In order to prevent damage to the O-ring seal, use the following procedure.

7. Use the following procedure in order to install the O-ring seal.

7.1.	Install the O-ring seal onto the frame, field and brush holder group in the normal position. The O-ring seal is in the normal position when the seal is against the shoulder on the field frame that will abut the installed commutator end frame.

7.2.	Carefully roll the O-ring seal out of the normal position and up onto the major outer diameter of the field frame.

7.3.	Allow the seal to remain on the outer diameter of the field frame until the commutator end frame is partially installed.




8. Use the following procedure in order to install the commutator end frame.

8.1.	Align the marks on the commutator end frame and the frame and field assembly made at disassembly.

8.2.	Position the commutator end frame onto the frame and field assembly.

8.3.	Leave a gap slightly larger than the thickness of the O-ring seal.




9. Use the following procedure in order to install the brush plate screws.

9.1.	Use a scribe or a similar tool in order to align the tapped holes in the brush holder assembly to the screw holes in the commutator end frame.

9.2.	Install the brush plate screws.

Tighten
Tighten the brush plate screws to 2.8 N·m (25 lb in).




10. Use the following procedure in order to install the through-bolts.

10.1.

Position the through-bolts.

10.2.

Tighten the through-bolts by hand, but do not close the gap between the commutator end frame and the frame and field assembly where the O-ring seal will be located.

10.3.

Roll the O-ring seal down into the normal position. The normal position is between the commutator end frame and the frame and field assembly.

10.4.

Align the timing ribs on the edge of the commutator end frame to the timing spots on the frame and field assembly in order to ensure proper alignment of the brushes.

10.5.

Although the marks are located in 2 places on the motor, the marks will only match in 1 way.

Tighten
Tighten the through-bolts to 8.5 N·m (75 lb in).




11. Use the following procedure in order to install the motor lead onto the frame and field assembly.

11.1.

Remove the nut from the terminal on the solenoid.

11.2.

Install the motor lead terminal.

11.3.

Reinstall the solenoid motor terminal nut.

Tighten
Tighten the solenoid motor terminal nut to 11 N·m (100 lb in).