General Motors — Engine Alignment
Adjustments · Engine mounts / propeller shaft coupling
From a General Motors owner's manual covering: Carb 5.7L, MP 5.0L, MP 5.7L, MP 6.0L. Check it applies to your exact model before use.
Before you start
- Engine must be properly aligned, or vibration, noise and damage to the transmission output shaft oil seal and bearings may result.
Procedure
- Check the mating surfaces on the transmission and the propeller shaft couplings for cleanliness and flatness.
- Center the propeller shaft in the shaft log by pushing/lifting and moving port/starboard, placing the shaft in the middle of the movement.
- Butt the propeller shaft coupling against the transmission coupling; the shoulder should engage the recess with no resistance.
- Check for angular misalignment with a 0.003 in. (0.07 mm) feeler gauge at 90-degree intervals.
- If misaligned, adjust the engine mounts: loosen the lag bolt 1/4 turn and turn the adjusting sleeve to raise or lower the engine; turn both front (or rear) adjusting sleeves equally.
- For left/right adjustment, loosen the trunnion clamping bolt and the nut on all four mounting brackets and move the engine as necessary.
- Secure the engine mounts.
- Connect the propeller shaft coupling to the transmission coupling and tighten the bolts and nuts to specifications.
Tools required
- mount adjusting tool or 3/8 in. or 1/2 in. diameter rod Amazon
- 0.003 in. (0.07 mm) feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Coupling faces parallel within 0.003 in. (0.07 mm)
- Propeller coupling torque 50 (68) Lb-Ft (N.m)
- Trunnion bolts torque 45 (61) Lb-Ft (N.m)
- Trunnion must not extend over 1.0 in. (25.4 mm) from the mounting brackets
Source: General Motors owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.