1. Use a puller to compress the primary shaft retaining ring...
2. ...and remove it from the gear block groove.
3. Unscrew the centering sleeve of the primary shaft.
4. Press the rear bearing of the primary shaft from the journal of the gear block...
5. ...and remove the bearing from the shaft.
Note: The snap ring and 5th gear pinion that hold the input shaft rear bearing to the shaft were removed during transmission disassembly.
6. Release the retaining ring of the III and IV drive gear block...
7. ...and remove the ring.
8. Remove the primary shaft itself from the gear block.
9. If necessary, press the III and IV gear block off the journals of the I and II gear block, as well as the reverse gear...
10. ...and separate the gear blocks.
11. Inspect the primary shaft and gear block. There should be no chips, wear marks or pitting on the working surfaces of the gear teeth, and no chips, pitting or dents on the ends of the gear splines. The bearing, lubricated with transmission oil, should rotate easily, without noise, knocking or jamming. There should be no signs of fatigue damage on the surfaces of the rolling elements. The bearing separator should not be damaged. When replacing the primary shaft, check that it moves easily in the hub of the driven clutch disc.
12. Assemble the primary shaft in the reverse order of disassembly. Press the rear bearing onto the shaft, applying force only to the inner ring, otherwise the bearing will be damaged.
(Original version of the article on the website: CHEVYMAN)