Differential - 7.5" to 9.5" GMC Sonoma Syclone

AXLE RATIO & IDENTIFICATION

To determine the drive axle ratio, refer to the correct DRIVE AXLE RATIO IDENTIFICATION article.

DESCRIPTION

Note. The 8 1/2" ring gear differential is also used as front drive axle on K15/25 models. These models may also be equipped with a Dana front drive axle. Refer to DRIVE AXLE - DANA FULL- FLOATING article in this section.

Axle assembly is hypoid gear type with integral carrier housing. It is used on Light Duty emission vehicles with semi-floating axles. Pinion bearing preload is made with a collapsible spacer. Differential side bearing preload adjustment and drive pinion depth adjustment are made by using shims.

A removable housing cover permits inspection and minor servicing of differential without removing axle from vehicle. Service procedures are same for all assemblies, except for torque specifications and special tool numbers. Astro and Safari use 7 5/8" ring gear. "S" and "T" series use 7 1/2" and 7 5/8" ring gears. All other models use 8 1/2" and 9 1/2" ring gears.

Scheme 1

Scheme 2

1. Raise vehicle. Support with jack stands. Remove wheels and brake drums. Place drain pan below cover. Loosen but do not remove differential cover bolts. Break cover loose and catch lubricant in drain pan. Remove differential cover bolts and remove cover.
2. Remove differential pinion shaft lock bolt. On axles without locking differential, remove differential pinion shaft. Push flanged end of axle shaft toward center of vehicle. Remove "C" lock from button end of axle shaft.
3. Remove axle shaft from axle housing, being careful not to damage seal. Repeat procedure for other side. (Scheme 1)
4. On axles with locking differential, partially remove pinion shaft. Rotate differential case until pinion shaft touches edge of housing. Reach into case with screwdriver and rotate "C" lock until its open end points directly inward. When "C" lock is correctly positioned, axle shaft can be pushed inward, allowing "C" lock to be removed. Remove axle shaft. (Scheme 2) CAUTION: DO NOT hammer on axle shaft. It should slide easily when "C" lock is correctly positioned. When removing axle shaft on 9 1/2" ring gear axle, be sure thrust washer in differential case does not slip out.
5. With axle shaft removed, insert Bearing Remover (J-22813-01 for 7 1/2" and 7 5/8"; J-23689 for 8 1/2"; and J-29712 for 9 1/2" ring gears) into axle housing behind bearing. Attach Slide Hammer (J-2619) and Adapter (J-2619-4 for 7 1/2" and 7 5/8"; J-2619-01 for 8 1/2" and 9 1/2" ring gears) to bearing remover, and remove axle bearing and axle seal.

Installation

1. To install, reverse removal procedure. Using Bearing Installer (J-23765 for 7 1/2" and 7 5/8"; J-23690 for 8 1/2"; and J-29709 for 9 1/2" ring gears), install axle shaft housing bearing until bearing installer bottoms against housing shoulder.
2. Using Seal Installer (J-23771 for 7 1/2" and 7 5/8"; J-21128 for 8 1/2"; and J-29713 for 9 1/2" ring gears), install axle shaft housing seal until it is flush with outer edge of axle tube. After installing axle shaft and "C" lock, pull axle shaft outward so "C" lock seats in side gear counterbore. Install pinion shaft and pinion shaft lock bolt. Tighten lock bolt to specification. Refer to the «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) table at end of article.

Removal

1. Raise vehicle and allow axle assembly to hang free. Remove pinion flange bolts and position drive shaft out of way.
2. Rotate pinion shaft through several revolutions using an INCH lb. torque wrench. Note and record pinion bearing preload. Mark relationship of pinion flange and shaft for reassembly. Count number of exposed threads on pinion shaft.
3. Hold flange with Companion Flange Holder (J-8614-01) and remove self-locking nut. Using Pinion Flange Remover (J-8614-1, 2 and 3 for 7 1/2" and 7 5/8"; and J-8614-01 for 8 1/2" and 9 1/2" ring gears), remove pinion flange. Pry pinion seal from housing. CAUTION: Be careful not to damage differential carrier when removing pinion seal.

1. Inspect pinion flange oil seal surface, drive splines, ears and bearing contact surface. Replace pinion flange (if necessary). Pack oil seal lip cavity with lithium base extreme pressure lubricant. Place pinion seal in bore.
2. Using Seal Installer (J-23911 for 7 1/2" and 7 5/8" ring gears), Gauge Plate (J-22804-1 for 9 1/2" ring gear) and Seal Installer (J-23836 for 8 1/2" and 9 1/2" ring gears), drive pinion seal into place.
3. Make sure oil seal is square in carrier. Pack cavity between end of pinion splines and pinion flange with a non-hardening sealer. Using Companion Flange Holder (J-8614-01), install flange on pinion shaft.
4. Install washer and nut in original position, taking note of scribe marks and number of exposed threads. Measure pinion preload. Tighten nut in small increments until preload exceeds original figure by 3-5 INCH lbs. (.3-.6 N.m). Install drive shaft and lower vehicle. CAUTION: DO NOT hammer flange onto pinion shaft, as ring gear and pinion will be damaged.

Removal & Installation

1. Raise vehicle. Using jack stands, support vehicle at frame. Allow differential to hang free. Drain lubricant. Remove rear wheels and brake drums. Remove parking brake cable. Disconnect drive shaft and brake lines. Disconnect vent hose from vent fitting at axle housing. Support axle housing with floor jack under center of carrier. Disconnect shock absorbers at axle housing.
2. Disconnect height sensing and brake proportional valve linkage (if equipped). Remove stabilizer shaft (if equipped). Remove "U" bolt, nuts, washers, spacers and spring plates from axle assembly. Slowly lower floor jack. Remove axle assembly from vehicle. To install axle assembly, reverse removal procedure. Bleed brake system.

DIFFERENTIAL ASSEMBLY

Note. Check and record ring gear backlash and pinion bearing preload before disassembly.

Disassembly

1. Remove axle shafts as previously described. Roll out differential pinions and thrust washers. Mark pinions and thrust washers (left and right) for reassembly. Remove side gears and thrust washers. Mark side gears and thrust washers (left and right) for reassembly.
2. Mark differential bearing caps and housing for reassembly. Loosen bearing cap bolts and tap bearing cap surfaces to loosen caps. Using pry bar inserted in differential carrier, pry against housing at differential window to remove carrier. CAUTION: Be careful, as carrier bearings are preloaded. Carrier will fall free after being pried past a certain point.
3. After removing carrier, place shims with appropriate bearing cups. Install bearing caps onto housing in their original position before removal. Using Differential Side Bearing Remover (J-22888) and Adapter (J-8107-2 for 7 1/2" and 7 5/8" ring gears; J-8107-4 for 8 1/2"; and J-8107-3 for 9 1/2" ring gears), remove differential side bearings. NOTE: Ring gear bolts have left-hand threads.
4. Remove ring gear bolts. Tap ring gear off carrier using a soft drift and hammer. Using an INCH lb. torque wrench, check torque required to rotate drive pinion. If no preload reading is obtained, check for looseness of pinion assembly. Looseness indicates pinion bearings should be replaced.
5. Install Companion Flange Holder (J-8614-01) on flange, with holder notches toward flange. Remove pinion nut and washer. Remove flange. Install pinion nut halfway on pinion. Install differential cover using 2 bolts. Tap end of pinion (using soft drift and hammer) to remove pinion. CAUTION: DO NOT damage pinion bearings when removing pinion from differential housing.
6. Remove differential cover and pinion assembly. Remove pinion oil seal and front bearing from housing. Remove collapsible spacer from pinion. Remove inner bearing and shim from pinion. Using Bearing Remover (J-25320 for 7 1/2" and 7 5/8"; J-8612-B for 8 1/2"; and J-22912-01 on 9 1/2" ring gears), press bearing from pinion.
7. Remove bearing cups from axle housing using hammer and punch in slotted areas. Inspect bearings and bearing cups, and replace them as required. Discard oil seal, pinion nut and collapsible spacer.

Cleaning & Inspection

Clean all parts in cleaning solvent. Inspect all bearings, bearing cups, races and rollers for chipping or excessive wear. Inspect axle shaft, ring gear and pinion for scoring, cracking or chipping. Inspect differential case, pinion side gears, thrust washers and pinion shaft for cracks or excessive wear.

Reassembly

1. Lubricate all parts with gear oil. Install side gears and thrust washers into case as marked in disassembly. Install pinion gears into case without thrust washers. Install one pinion gear onto side gears and rotate gears until pinion gear is exactly opposite from pinion shaft opening in case. Place second pinion gear onto side gears so that pinion gear hole is exactly opposite from pinion shaft opening in case.
2. Verify that pinion shaft fits through pinion gears. Install pinion gear thrust washers. Install pinion shaft and pinion shaft lock bolt. Tighten bolt to specification. Install ring gear squarely onto case. Tighten ring gear bolts evenly and alternately to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) table.
3. Install inner pinion bearing onto pinion using Bearing Installer (J-5590). Drive bearing onto pinion until bearing is seated on pinion shims. Install a new collapsible spacer. Install pinion into axle housing. Install outer bearing onto pinion using Bearing Installer (J-5590). Hold pinion forward from inside housing while driving bearing onto pinion.
4. If a new ring and pinion and/or bearings were installed, refer to procedures in both «DRIVE PINION DEPTH»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) and «SIDE BEARING PRELOAD»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) . Install pinion oil seal and pinion flange. Refer to sub-heading «PINION FLANGE & OIL SEAL»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) . To complete installation, see «BACKLASH & FINAL ASSEMBLY»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95__backlash-final-assembly) .

Scheme 3

1. Drive pinion rear bearing shim thickness must be determined whenever a new axle housing, ring and pinion set, or pinion bearings are installed. Shim pack thickness is determined by using Pinion Setting Gauge Set (J-21777).
2. If removed, install pinion bearing cups into housing. Place lubricated pinion bearings into cups. Position Gauging Plate (J-23597-11 for 7 1/2" and 7 5/8"; J-21777-29 for 8 1/2"; and J-21777-85 for 9 1/2" ring gears) and rear pinion bearing pilot on preloaded stud.
3. Install pinion bearing through rear of housing. Install front pinion bearings and Bearing Disc (J-21777-42). Tighten hex nut until snug. Rotate bearings to insure proper seating. Hold preload stud stationary with a wrench on flats. Tighten hex nut until 20 INCH lbs. (2.2 N.m) are required to rotate bearings. (Scheme 3)
4. Mount side bearing Gauging Discs (J-21777-45 for 7 1/2", 7 5/8" and 8 1/2"; and J-21777-86 for 9 1/2" ring gears) on ends of arbor. Place arbor into carrier making sure discs are properly seated. Install side bearing caps and bolts. Tighten bolts to avoid movement.
5. Position dial indicator on mounting post of arbor, with contact button resting on top surface of plunger. Set dial indicator at zero. Push indicator down on indicator shaft until needle rotates 3 to 4 revolutions to right, then tighten in this position.
6. Place plunger onto gauging area of gauge plate. Rock plunger rod slowly back and forth across gauging area until dial indicator reads greatest deflection.
7. Set indicator to zero. Repeat rocking action several times to verify setting. Once zero reading is obtained, swing plunger until it is removed from gauging area.
8. Dial indicator will now read required pinion shim thickness for a nominal pinion. Record this reading. Check drive pinion for painted or stamped markings on pinion stems, or for a stamped code number on small end of pinion gear.
9. If marking is a plus (+), add that many thousandths of an inch from indicator reading. If marking is a minus (), subtract that many thousandths of an inch from indicator reading. This will then be required thickness of rear pinion bearing shim pack. NOTE: If no markings are found on pinion, use dial indicator reading as shim thickness.
10. Remove bearing caps and gauging tool from housing. Place selected shim pack on pinion gear. Using a press, install lubricated pinion bearing onto pinion shaft.
11. Install a new collapsible spacer over pinion gear shaft. Position pinion assembly in housing. While holding pinion forward, carefully drive front pinion bearing onto pinion gear shaft until a few threads are exposed.
12. Install seal, pinion flange, washer and nut. Tighten nut until all end play is removed. Rotate pinion several times to seat bearings. Check preload using an INCH lb. torque wrench.
13. Continue tightening nut and checking preload until specified preload is obtained. See «AXLE ASSEMBLY SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95) table. DO NOT back off nut to lessen preload.
14. If preload is exceeded, a new collapsible spacer must be installed, and nut must be retightened until proper preload is obtained.

7 1/2", 7 5/8" & 8 1/2" Ring Gears

1. Side bearing preload is adjusted by varying the thickness of both left and right side bearing shims equally. Lubricate bearings and place differential assembly into position in housing. Hold in place by hand.
2. Install Bearing Strap (J-22779-6) on left bearing. Tighten bolts evenly to a snug fit. Install right bearing cap. Tighten bolts to a snug fit.
3. Position ring gear tight against pinion so backlash is .000-.001" (0-.025 mm). Insert Gauge (J-22779) between left bearing cup and carrier housing.
4. While moving gauge up and down, tighten adjusting nut on end of gauge until a slight drag is felt. Tighten lock bolt on side of tool.
5. Install adjustment spacer and shim between right bearing cup and axle housing. Determine bearing preload by inserting progressively larger feeler gauges between carrier and shim. The point just before drag begins is the correct feeler gauge thickness. This is the zero setting without preload.
6. Remove bearing strap, gauge, spacer, shim, feeler gauge and differential case from axle housing. Using a micrometer, measure and average readings in 3 places on gauge. Record measurement.
7. Add together dimensions of shim, spacer and feeler gauge. Subtract .010" (.25 mm) from ring gear (left) side measurement and add .010" (.25 mm) to opposite (right) side measurement. This allows for correct backlash adjustment.
8. To obtain correct preload, add .004" (.10 mm) to both measurements. The total is correct shim pack thickness for each side. For example: Ring Gear Side (Left) Shim Pack: .250" (Gauging Tool Measurement) -.010" (Backlash Adjustment) +.004" (Bearing Preload) ----- =.244" (Ring Gear Side Shim Pack) Opposite Ring Gear Side (Right) Shim Pack: .265" (Combined Measurement Total) +.010" (Backlash Adjustment) +.004" (Bearing Preload) ----- =.279" (Opposite Ring Gear Side Shim Pack)
9. Install ring gear side shim first. Wedge opposite side shim between bearing cup and spacer. Install shim so chamfered side is against spacer. NOTE: If shim is not chamfered enough and scrapes spacer when it is installed, file or grind chamfer before installation.
10. It may be necessary to partially remove differential when right side shim is installed. Tap shim into place with a soft-faced hammer. Tighten bearing cap bolts to specifications. Check backlash. See «BACKLASH & FINAL ASSEMBLY»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95__backlash-final-assembly) .

9 1/2" Ring Gear

1. Differential side bearing preload is adjusted by adjusting nut in differential bearing bore (right side). The bore and bearing cap provide the mating threads for the bearing nut. Install bearing cups to differential bearings in original locations.
2. Install differential case into axle housing assembly. Install bearing shims. Push case away from pinion towards axle housing and install adjusting nut. Tighten nut with Spanner Wrench (J-24429). Turn pinion to seat bearings.
3. Back off adjusting nut. Install bearing caps and bolts loosely in their original positions. Turn adjusting nut until nut contacts shim. Tighten nut 3 additional slots.
4. Tighten bearing cap bolts to specifications. Install adjusting nut lock bolt. Tighten to specification. Check backlash adjustment. See «BACKLASH & FINAL ASSEMBLY»(/gmc/sonoma-syclone/1991-1992/remont/differentials-drive-axles/#differential-75-to-95__backlash-final-assembly) .

BACKLASH & FINAL ASSEMBLY

1. Rotate case several times to seat bearings. Check backlash at 4 locations around outside edge of ring gear using a dial indicator mounted to axle housing. Install indicator in line with gear rotation and perpendicular to tooth angle. Pinion must be held steady while taking readings. Variation should not exceed.002" (.05 mm).
2. If backlash is incorrect, adjust side bearing shims as necessary. After adjustment is completed, perform gear tooth contact pattern check. See «GEAR TOOTH CONTACT PATTERNS»(/gmc/sonoma-syclone/1991-1992/remont/drivelineaxles/#gear-tooth-contact-patterns-general-information) article. Install axle shafts and housing cover. (Scheme 4)

Note. Total shim pack thickness for right and left side combined must not be changed. If a shim is removed from one side, same thickness shim must be added to other side.

AXLE ASSEMBLY SPECIFICATIONS

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 4

See also:
• GEAR TOOTH CONTACT PATTERNS
• TORQUE SPECIFICATIONS
• BACKLASH & FINAL ASSEMBLY