Alternator Bearing replacement question

[dkamp]

On a square back alternator, when you press in the new bearings, how do you know how far to press them on?

 

[Vaanth]

On a square back alternator, when you press in the new bearings, how do you know how far to press them on?

For the drive, or front, end shield (aka. case half), the bearing in the end shield recess and press in until it bottoms. Install the retainer. Then, supporting the rotor back end, align the bearing/end shield,and using a sleeve that fits around the shaft and on the bearing inner face (or Chrysler tool C-3858), press the bearing down on the shaft until it bottoms. The collar on the rotor shaft limits and places the bearing correctly.

To install the rear bearing properly in the rear, or rectifier, end shield use Chrysler tool C-4201 (parts C-4201-1 and C-4201-2). Position the rectifier end shield bearing on base of tool C-4201 (C-4201-1). Place the rear end shield on top of the bearing aligning it to press evenly. Use the other part of tool C-4201 (C-4201-2) on end shield, and press it into place until it bottoms. The lower part of the tool limits and places the bearing correctly.

Without the Chrysler tool, support the rear, or rectifier, end shield around the bearing area with an open sleeve or similar. Align the bearing in the opening to press in evenly. Using a cylindrical block slightly smaller in diameter than the bearing press in until the bearing is as follows:

- For an aftermarket smooth bearing, in a 1972 -1977 alternator, press until the surface of the bearing is slightly above the surface of the end shield.

- For an original ribbed bearing, in a 1972 -1977 alternator, press until the surface of the bearing is slightly higher above the surface of the end shield than a smooth bearing.

- For an aftermarket smooth bearing, in a 1978 -1987 alternator, press until the edge surface of the bearing is slightly more than 1/8" below the surface of the end shield.

- For an original ribbed bearing, in a 1978 -1987 alternator, press until the edge surface of the bearing is about 1/8" below the surface of the end shield.

NOTE: Describing the depth of the surface in relation to the shield surface is a little difficult to do quantitatively, but after doing a few, one gets a feel for it. Depending on component variances and possible manufacturer depth difference, the depth can vary.

NOTE:Adjustment may be required if binding occurs when the unit is assembled. Before tightening the shield mating bolts fully, or installing brushes, spin the rotor and feel and listen for roughness and binding. If detected, disassemble, and press the rear bearing back slightly, until the rotor spins freely.

NOTE: If using the bearing grease shield on the slip ring end of the rotor, slightly more clearance may be required to prevent rubbing of the shield on the bearing.

Following are a few images of alternators I have done for reference:

1972-1977 with smooth bearing. Bearing surface slightly above shield.

1972-1977 with smooth bearing. Bearing surface even with shield surface.

1978-1987 with ribbed bearing. Bearing surface edge ~1/8" below the shield surface.

NOS 1978-1987 with ribbed bearing. Bearing surface edge ~1/8" below the shield surface. This bearing has never been out, but I did disassemble the alternator to inspect and change the pulley.

I didn't have an earlier alternator with the ribbed bearing handy to show.