This procedure covers removal, inspection, and replacement of the limited slip differential clutch pack in the 1966 Corvette rear axle, including complete disassembly of the differential carrier and proper setup of clutch pack preload.

Warnings

Tools required

Parts

• Limited slip clutch pack kit × 1 — Use OEM specification or aftermarket equivalent for Positraction
• Differential cover gasket × 1 — Use OEM specification
• Differential side bearing shims (assorted) × 1 — Use OEM specification
• Clutch pack shims (assorted) × 1 — Typically 0.030, 0.032, 0.034 inch
• Pinion shaft lock bolt × 1 — Use OEM specification
• Gear marking compound × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake.
2. Chock front wheels securely.
3. If vehicle was recently driven, allow differential to cool for minimum 2 hours.
4. Raise rear of vehicle and support on jack stands positioned under frame rails.
5. Remove both rear wheels to improve access and reduce weight on suspension.
6. Mark driveshaft-to-pinion flange orientation with paint pen for proper reassembly indexing.
7. Place drain pan under differential cover.
8. Clean exterior of differential housing thoroughly to prevent contamination during disassembly.

Procedure

1. 1

   Drain differential and remove cover
   Remove all differential cover bolts (verify exact count for this axle) working in a cross pattern. Allow cover to remain loosely in place until most oil has drained from bottom. Once drained, fully remove cover and gasket. Clean all gasket material from both cover and housing mating surfaces using scraper and solvent. Inspect drained oil for metal particles or debris indicating other internal damage.
2. 2

   Remove pinion shaft and axles
   Rotate ring gear until pinion shaft lock bolt is accessible through inspection window. Remove pinion shaft lock bolt. Using brass punch if needed, tap pinion shaft out toward ring gear side until it clears differential case. Push both axle shafts inward slightly and remove C-clips from axle shaft button ends inside differential. Carefully withdraw both axle shafts from housing tubes. Set axle shafts aside on clean surface.
3. 3

   Mark bearing cap orientation
   Before removing any carrier components, use marker or punch to clearly mark the driver side and passenger side bearing caps and their corresponding carrier housing legs. These caps are machined as matched sets and must be reinstalled in exact original orientation. Mark the differential case halves as well for proper reassembly orientation.
4. 4

   Install differential spreader tool
   Install differential spreader tool onto carrier housing following manufacturer instructions. Mount case spreading dial indicator so it measures the spread at the top of the carrier between the bearing cap mounting surfaces. Zero the dial indicator. Slowly turn spreader tool while watching dial indicator. Spread carrier housing exactly 0.010 inch maximum. Do not exceed 0.015 inch spread or permanent housing damage will occur.
5. 5

   Remove bearing caps and extract differential assembly
   With carrier spread, remove 4 bearing cap bolts (2 per side). Carefully remove both bearing caps, keeping them with their respective shims. Using pry bars positioned behind ring gear, carefully work differential assembly upward and out of carrier housing. Keep side bearing outer races with their respective bearings and note any shims behind each bearing. If bearings remain in carrier, use bearing puller to remove them and keep matched to correct side.
6. 6

   Release spreader and secure differential
   Once differential assembly is removed, immediately release pressure on differential spreader tool to prevent carrier distortion. Mount differential assembly in vise using soft jaws or wood blocks to protect ring gear. Do not overtighten vise.
7. 7

   Disassemble differential case halves
   Remove the ring gear bolts (verify exact count for this axle) if ring gear removal is necessary for access. Remove the case half bolts (verify exact count for this Positraction unit) that join the two halves of the differential case together. Carefully separate case halves, keeping all internal components organized. The limited slip unit will be inside one case half.
8. 8

   Remove and inspect old clutch pack
   Remove the limited slip clutch pack assembly, noting exact order and orientation of all clutches, plates, and shims. Count all components and measure clutch pack height with micrometer. Standard clutch packs contain alternating friction discs and steel plates. Inspect all friction surfaces for glazing, scoring, or uneven wear. Inspect steel plates for warping or heat discoloration. Measure side gear thrust surfaces for wear. Any wear or damage requires replacement.
9. 9

   Clean all differential components
   Thoroughly clean both case halves, side gears, spider gears, and all mating surfaces using solvent and parts brush. Remove all old gear oil, debris, and clutch friction material residue. Dry completely with compressed air. Inspect case halves for cracks, especially around bolt holes and bearing mounting surfaces. Inspect side gear and spider gear teeth for excessive wear or damage.
10. 10

    Install new clutch pack assembly
    Install new clutch pack components into differential case half in exact order specified by clutch pack kit instructions. Typically this alternates friction discs (splined to case) with steel plates (tabbed to side gear). Begin with proper preload shim thickness based on old measurements or kit instructions. Install side gears into clutch pack assembly. Ensure all components seat fully and rotate freely.
11. 11

    Measure and set clutch pack preload
    Before assembling case halves, clutch pack preload must be verified. Install dial indicator to measure side gear end play. Assemble case halves loosely without ring gear. Using inch-pound torque wrench, measure rotational torque required to turn one side gear while holding the other stationary. Proper breakaway torque specification must be confirmed against the factory GM service manual for this Positraction unit (verify exact value). Adjust by changing preload shim thickness: thicker shim increases preload, thinner decreases. Repeat measurement until within specification.
12. 12

    Reassemble differential case
    Once clutch pack preload is verified correct, apply thin coat of gear oil to all clutch surfaces. Align case half marks made during disassembly. Install 4 case bolts with medium-strength threadlocker. Tighten case bolts in cross pattern to secure case halves. If ring gear was removed, clean ring gear bolt holes and apply medium-strength threadlocker. Install ring gear with bolts, tightening in star pattern.
13. 13

    Install side bearings and prepare for installation
    If side bearings were removed, press or drive new bearings onto differential case hubs using appropriate bearing driver. Ensure bearings are fully seated against case shoulders. Install original shim packs behind each bearing outer race, keeping left and right sides identified.
14. 14

    Install differential assembly into carrier
    Apply thin coat of gear oil to all bearing surfaces. Install differential spreader tool and spread carrier housing 0.010 inch as before. Carefully lower differential assembly into carrier housing, aligning bearing outer races with their bores. Ensure shims are properly positioned behind bearing races. Install bearing caps in their original marked positions. Start all 4 bearing cap bolts finger tight.
15. 15

    Set bearing preload and backlash
    Release carrier spreader tool slowly while simultaneously snugging bearing cap bolts to pull assembly down into position. Tighten bearing cap bolts to secure differential. Mount dial indicator to measure ring gear backlash at several teeth around ring gear. Proper backlash specification must be confirmed against the factory GM service manual for this axle (verify exact value). Adjust by moving shims from one side to opposite side: moving shim from ring gear side to opposite side increases backlash. Check that bearing preload feels correct when rotating pinion by hand (slight drag). Verify ring gear-to-pinion tooth contact pattern using gear marking compound.
16. 16

    Install pinion shaft and axle C-clips
    Rotate ring gear until pinion shaft holes in case and side gears align. Insert pinion shaft through case and through spider gear set until fully seated and lock bolt hole aligns. Install new pinion shaft lock bolt with medium-strength threadlocker. Insert both axle shafts fully into axle tubes and through side gear splines. Push axles outward and install C-clips into axle shaft grooves. Pull outward on each axle to verify C-clips are properly seated.
17. 17

    Install cover and refill differential
    Clean cover and housing mating surfaces again if needed. Apply thin bead of RTV silicone gasket maker to cover or install new paper gasket per preference. Install cover with all 10 bolts, tightening in cross pattern. Allow RTV to cure per manufacturer instructions before filling if used. Fill differential through fill plug hole with 80W-90 GL-5 gear oil plus the required limited-slip (Positraction) friction modifier additive until oil reaches bottom of fill hole threads (verify factory capacity). Install fill plug.

Reassembly

1. Reinstall rear wheels and tighten lug nuts to proper specification.
2. Lower vehicle to ground and perform final lug nut torque verification.
3. Test drive vehicle and verify limited slip operation by performing slow, tight turns on dry pavement and listening for clutch chatter or abnormal noises.
4. Recheck differential oil level after first 50 miles of operation and inspect cover for leaks.

Verification

• With one wheel off ground, rotate that wheel by hand. The opposite wheel should rotate in the same direction (both forward or both backward) confirming limited slip operation.
• Perform slow figure-8 turns in empty parking lot. Limited slip differential should engage smoothly without excessive chatter or binding.
• Check for oil leaks around differential cover after test drive.
• Verify no abnormal noise from rear differential during acceleration, deceleration, and turning.
• Confirm smooth engagement of limited slip during low-speed tight turns, typical slight chatter is normal on dry pavement.

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