Differential: Other Ford Thunderbird X

DRIVE SHAFT

Note. For models with independent rear suspension, see DRIVE AXLE - REAR article for axle shaft overhaul.

Gear Tooth Contact Pattern

1. Paint ring gear teeth with marking compound. Wrap cloth or rope around drive pinion flange to act as brake. Rotate gear until clear contact pattern is obtained.
2. Contact pattern will indicate whether correct pinion bearing mounting shim has been installed and if drive gear backlash has been set properly. Backlash between drive gear pinion must be maintained within specified limits until correct tooth pattern is obtained.

Scheme 11

1. With no change in backlash, moving pinion further from ring gear moves drive pattern toward heel and top of tooth, and moves coast pattern toward toe and top of tooth.
2. With no change in backlash, moving pinion closer to ring gear moves drive pattern toward toe and bottom of tooth, and moves coast pattern toward heel and bottom of tooth.
3. With no change in pinion shim thickness, an increase in backlash moves ring gear further from pinion. Both drive and coast patterns move toward heel and top of tooth.
4. With no change in pinion shim thickness, a decrease in backlash moves ring gear closer to pinion gear. Both drive and coast patterns move toward toe and bottom of tooth. (Scheme 11): Drive Axle Gear Tooth Patterns

Scheme 12

Scheme 13

1. Assemble Pinion Depth Gauge (T79P-4020-A). Install aligning adapter, gauge disc and screw. Gauge disc thickness should be.89" (23 mm) for 7.5" ring gear and 1.19" (30 mm) for 8.8" ring gear. (Scheme 12) Place rear pinion bearing over aligning adapter and into bearing cup of carrier housing.
2. Install front pinion bearing into front bearing cup. Place handle onto screw and tighten to 20 INCH lbs. (2.25 N.m). (Scheme 13) Ensure pinion depth measuring tool is properly installed and tightened.
3. Apply a light film of oil to pinion bearings. Rotate gauge block several times to seat bearings. Rotational torque on gauge block assembly should be 20 INCH lbs. (2.25 N.m) with new bearings. Final position of gauge block should be 45 degrees above axle shaft center line.
4. Clean differential bearing bores thoroughly and install gauge tube. Tighten differential bearing cap bolts to specification. See «TORQUE SPECIFICATIONS»(ref-46564-S04015156652001011500000) table. Use flat pinion shims as a gauge for shim selection. Hold gauge block in proper position and measure clearance between gauge block and tube.
5. Correct shim selection is accomplished when a slight drag is felt as shim is drawn between gauge block and tube. Shims are available in various thicknesses. Install correct shim on pinion for reassembly. Pinion bearings must be installed in the same location as during pinion depth measurement.

PINION BEARING PRELOAD

1. Place preselected shim on pinion. Press bearing onto pinion until bearing and shim are firmly seated against shoulder of pinion. Install new collapsible spacer on pinion.
2. Lubricate bearings with axle lubricant. Install front pinion bearing in housing. Install new pinion oil seal. Lubricate pinion oil seal.
3. Insert companion flange into seal and hold firmly in place. From rear of housing, install pinion shaft into companion flange. Start a NEW pinion nut on pinion.
4. Gradually tighten pinion nut while holding companion flange. Using INCH lb. torque wrench, check torque required to maintain rotation of pinion (pinion bearing preload) through several revolutions. Check for pinion bearing preload often. As soon as preload is measured, rotate pinion in both directions several times to seat bearings.
5. Tighten the pinion nut and continue to measure pinion bearing preload until the specified pinion torque is obtained. See «TORQUE SPECIFICATIONS»(ref-46564-S04015156652001011500000) table. Ensure pinion bearing preload is within specification. See «AXLE ASSEMBLY SPECIFICATIONS»(ref-46564-S12752697412001011500000) table.
6. If bearing preload is exceeded before torque specification is reached, replace collapsible spacer. Install NEW pinion nut and repeat procedure. DO NOT loosen pinion nut to reduce pinion bearing preload.

Scheme 14

Scheme 15

1. With pinion depth set and pinion installed, place differential case and gear assembly, with bearings and cups, into axle housing. Install a.265" (6.73 mm) shim on left side (ring gear side) of differential.
2. Install left differential bearing cap with bolts finger tight. Select largest shim that will fit with a slight drag and install on right side (pinion gear side) of differential. Install right bearing cap and bolts. Tighten all differential bearing cap bolts to specification. See «TORQUE SPECIFICATIONS»(ref-46564-S04015156652001011500000) table at end of article.
3. Rotate gear assembly to ensure free operation. Check ring gear backlash. (Scheme 15) Ring gear backlash should be within specification. See «AXLE ASSEMBLY SPECIFICATIONS»(ref-46564-S12752697412001011500000) table. If ring gear backlash is within specification, go to step 7). If zero ring gear backlash is recorded, go to step 4). If ring gear backlash is not within specification, go to step 5).
4. If zero ring gear backlash is recorded, add.020" (.51 mm) to shim size on right side and subtract.020" (.51 mm) from shim size on left side. Check ring gear backlash.
5. If ring gear backlash is not within specification, increase shim thickness on one side and decrease shim thickness on opposite side by same amount. See «RING GEAR BACKLASH-TO-SHIM THICKNESS CONVERSION»(ref-46564-S29598193062001011500000) table for approximate shim change. (Scheme 14)
6. Install shim and differential bearing caps. Tighten differential bearing cap bolts. See «TORQUE SPECIFICATIONS»(ref-46564-S04015156652001011500000) table. Rotate gear assembly several times. Recheck ring gear backlash. If ring gear backlash is within specification, go to step 7). If backlash is not within specifications, repeat step 5).
7. Increase both left and right shim sizes.006" (.15 mm) and reinstall for correct bearing preload. Ensure shims are fully seated and gear assembly turns freely. Using marking compound, check gear tooth contact pattern. RING GEAR BACKLASH-TO-SHIM THICKNESS CONVERSION Required Change In Backlash In. (mm) Required Change In Shim Thickness In. (mm).001 (.03).002 (.05).002 (.05).002 (.05).003 (.08).004 (.10).004 (.10).006 (.15).005 (.13).006 (.15).006 (.15).008 (.20).007 (.18).010 (.25).008 (.20).010 (.25).009 (.23).012 (.30).010 (.25).014 (.36).011 (.28).014 (.36).012 (.30).016 (.41).013 (.33).018 (.46).014 (.36).018 (.46).015 (.38).020 (.51)