David Brown front axle – Differential assembly


Remove and Reinstall the Differential assembly

David Brown Differential assembly may be removed with differential housing and axle housing installed on tractor. It is necessary, however, to first remove left and right stub axle assemblies.
With stub axle assemblies and axle drive shafts removed, remove main drive shaft and steering cylinder. Support differential unit on floor jack and remove retaining bolts. Carefully move differential assembly out of housing and lower to floor.
Reinstall by reversing removal procedure. Tighten differential assembly retaining bolts to 68 N-m (50 ft.-lbs.) torque and drive shaft bolts to 54 N-m (40 ft.-lbs.) torque. Fill differential to correct level gear lubricant or equivalent.

OVERHAUL DIFFERENTIAL
Remove differential assembly and place in a stand with flange end toward floor. Mark bearing caps so they can be reinstalled in their original positions and remove. Remove adjuster rings. Remove differential bevel ring gear and cage as an assembly.


Fig. 1 - David Brown differential assembly showing component parts and their relative positions.

Remove pinion shaft locknut (31 — Fig. 1), then drive pinion shaft through flange (28) and carrier (1). Front spacer (22), shims (23) and rear spacer (24) should remain on pinion shaft as it is removed. Remove remaining bearing cups and shims from carrier (1) as necessary. Inspect bearings and spacers on pinion shaft and renew as necessary.
Mark end plate (8), cage (14) and bevel ring gear (15) so they may be reassembled in their original positions. Re-move carrier bearings and separate end plate (8) from cage (14). Remove axle gears, pinion gears and pin (10). Separate bevel ring gear from cage as necessary.
Bevel ring gear and pinion shaft are serviced as matched sets only and must be installed as such.
If bevel ring gear and pinion shaft, pinion shaft bearings or carrier are renewed, pinion shaft protrusion must be set. Reassemble by reversing disassembly procedure. Adjust carrier bearings and bevel gear backlash.

PINION SHAFT PROTRUSION AND BEARING PRELOAD
Special tool is required to set pinion shaft protrusion on David Brown front axle, and all bearings, cups and spacers to be used in final assembly must be installed.
Assemble pinion shaft in carrier minus shims (18—Fig. 1), oil seal (27), spacer (26), sealing washer (29), front spacer (22), shims (23) or rear spacer (24). Install flange (28), retaining washer (30), and locknut (31) on pinion shaft (16) and tighten locknut until all end play of pinion shaft is just removed, then tighten locknut just a small amount more to slightly preload bearings. Install special tool in carrier bearing bores as shown in Fig.2.


Fig. 2 - To set pinion shaft protrusion, install special tool set in carrier housing as shown.

Install shaft, probe and spacer  and locknut of special tool so probe point lightly contacts face of pinion shaft gear. Tighten locknut to lock probe in this position. Using a feeler gage, measure and record amount of gap between spacer and probe. See Fig.3.



Fig.3 - Measure gap between probe and spacer of special tool with a feeler gage.

Note protrusion correction mark etched on end of pinion shaft gear. This will be "O" or a plus (+) or minus (-) dimension. Note that dimension is given in thousandths of an inch.
Noting that special tool has a built in dimension of 0.030 inch (0.76 mm), substitute actual gap measurement and shaft correction number for figures shown in the following example to determine thickness of shims (18—Fig. 1) needed to correctly set pinion shaft protrusion.

Tool built in dimension 0.030 in. (0.76 mm)
Add or subtract dimension etched on pinion shaft -0.005 in. (0.13 mm)
Result is setting dimension "A"  0.025 in. (0.63 mm)
Measured gap . . . 0.055 in. (1.40 mm)
Minus setting dimension "A" determined above - 0.025 in. (0.63 mm)
Result is thickness of shims required  0.030 in. (0.77 mm)

Remove special tool, pinion shaft and inner bearing cup. Assemble correct thickness of shims into housing bore, then  reinstall  inner bearing cup.  Be sure cup seats against shims and housing counterbore.
Reassemble pin shaft with spacers (22 and 24 - Fig. 1) using 1.27 mm (0.050 inch) thick shims (23), but without spacer (26), oil seal (27) and sealing washer (29). Install flange (28), washer (30) and nut (31) on pinion shaft and tighten nut to 190 N-m (140 ft.-lbs.) torque. Turn shaft in both directions to seat bearings, then mount a dial indicator on carrier so probe contacts end of pinion gear and measure shaft end play. Remove pinion shaft and reduce thickness of shims (23—Fig. 1) an amount equal to measured end play. This procedure will provide zero end play and zero preload. However, a tolerance of plus or minus 0,05 mm (0.002 inch) is acceptable.
Reinstall pinion shaft with all spacers and seals. Tighten retaining nut to 190 N-m (140 ft.-lbs. torque.

DIFFERENTIAL CARRIER BEARINGS AND  BEVEL GEAR BACKLASH
On tractor models, adjustment of differential carrier bearings to provide proper bevel gear backlash and bearing adjustment is correlated with pinion shaft protrusion adjustment.
Install differential assembly, but do not securely tighten carrier bearing caps. Install adjuster rings and turn in until end play of differential in carrier is less than 0.05 mm (0.002 inch) without preloading bearings. Mount dial indicator, then move carrier assembly sideways as required to obtain correct bevel gear backlash of 0.18-0.23 mm (0.007-0.009 inch) by loosening one adjuster ring one notch at a time and tightening opposite adjuster ring the same amount each time. When bevel gear backlash and differential carrier bearings are properly adjusted, install adjuster ring locks and tighten carrier bearing cap bolts to 163 N-m (120 ft.-lbs.) torque.

MAIN  DRIVE SHAFT
Main drive shaft consists of a sliding yoke, drive shaft tube and two universal joints. To remove sliding yoke, mark its position for reassembly on correct splines, unscrew threaded cap and slide slip yoke off splines. Use conventional procedure to renew universal joints.
Install drive shaft with slip yoke at differential end and tighten bolts to 54 N-m (40 ft.-lbs.) torque.