David Brown front axle – Transfer gearbox


Drain oil from transfer case and transmission. Capacity is approximately 42 L (44 quarts). Remove front drive shaft. Engage front-wheel drive, then remove output shaft flange retaining nut (20). Remove platform or cab, if equipped. Remove fuel tanks. Disconnect selector cable from selector shaft (4). Remove left and right shift lever housings from transmission top cover. Remove bolts from transmission top cover, remove wedge and shims between top cover and clutch housing, and remove top cover using a suitable hoist. Remove bolt (37) and locknut (39), then slide coupler (38) connecting transfer gearbox input shaft to transmission bevel pinion shaft rearward. Remove selector cable bracket (44) and hydraulic pump inlet pipe connector. Support transfer gearbox with a hydraulic jack, then remove gearbox mounting bolts and lower gearbox from transmission housing.
When reinstalling, laminated gasket (1) must be the same thickness as original gasket, or layers peeled off to allow coupler (38) to slide freely onto input shaft (12) and bevel pinion shaft. Tighten transfer gearbox mounting bolts to 165 N-m (120 ft.-lbs.) torque. Tighten output shaft flange nut (20) to a torque of 190 N-m (140 ft.-lbs.). Install transmission top cover with wedge and same thickness of shims that were removed. Tighten three middle % inch bolts securing rear axle housing to top cover to 205-245 N-m (150-180  ft.-lbs.)  torque.  Tighten  remainder of top cover mounting bolts to 110-130 N-m (80-95 ft.-lbs.) torque. Tighten drive shaft flange bolts to 54 N-m (40 ft.-lbs.) torque. Complete installation by reversing removal procedure.


OVERHAUL TRANSFER GEARBOX

With transfer gearbox removed, disassemble as follows: Remove end plates (3 and 46—Fig. 16) and shims (36). Note position and thickness of shims (36). Drive input shaft (12) and idler shaft (34) out of housing (2). Remove input gear (13). Remove front bearing and cup (16). Remove output flange (23), cork seal (22) and washer (21). Remove oil seal housing (26) and output shaft end cover (43). Note thickness of shims (33). Drive output shaft (19) out of housing (2), remove the six bearing pads (18) and bearing and cup (27). Remove bottom cover (9) and drive roll pin (7) out of selector fork (6) and remove selector shaft (4). Remove selector fork, fixed gear (30) and sliding gear (29). Remove output gear (17) and idler gear (15). Remove selector shaft oil seal (5) and core plug (41).


Figure - Transfer gearbox used with David Brown front drive axle showing component parts and their relative positions


Clean and inspect all parts for excessive wear or damage. Lubricate all parts during reassembly.
Install idler gear (15) into bottom of transfer gearbox housing (2). Install output gear (17) into
housing with hub for sliding gear engagement towards front of housing. Place fixed gear (30) inside sliding gear (29) and install output shaft (19) into rearward side of bottom hole in housing, pushing it through output gear (17)
and partially through fixed gear (30). Oil slots on side of fixed gear (30) go against output gear (17). Spacer (31) and bearing (32) must already be assembled on output shaft (19). 

Install six bearing pads in output shaft, concave side against shaft, as it is pushed through output gear (17) and fixed gear (30), Install rear bearing cup (32), gasket (42), rear cover (43) and cable bracket (44) minus shims (33). Tighten bolts to 27 N-m (20 ft.-lbs.) torque. Install front bearing (27) and bushing (28) on output shaft and drive front bearing cup (27) into housing (2). Install oil seal (25) in oil seal housing (26) and install oil seal housing on transfer gearbox housing. Tighten bolts to 27 N- m (20 ft.-lbs.) torque. Hit end of output shaft (19) with a plastic hammer to seat bearings and cups.
Mount dial indicator on transfer gear box housing (2) so probe end contacts end of output shaft (19), Measure and record end play of output shaft. End play tolerance is 0-0.05 mm (0-0.002 inch) for new bearings and 0.05-0.10 mm (0.002-0.004 inch) for used bearings.

To determine proper shim (33) thickness, subtract 0.025 mm (0.001 inch) from dial indicator measurement if new bearings were installed, or subtract 0,076 mm (0.003 inch) from dial indicator measurement if original bearings are reused. The result is the required shim thickness to provide recommended end play.
Remove rear bearing cover (43) and install correct thickness of shims (33). Reinstall cover and tighten bolts to 27 N-m (20 ft.-lbs.) torque. Recheck end play and adjust shim thickness, if necessary, if not within tolerance.
Install oil seal (5) into housing (2) and place trunnion pins (40) in selector fork (6). Install selector fork in housing, making certain trunnion pins engage slot in sliding gear (29). Install selector shaft (4) through oil seal (5) and selector fork. Align roll pin holes in selector fork and shaft and install roll pin (7). Install core plug (41), bottom cover gasket (8) and bottom cover (9). Install flange (23), cork washer (22), washer (21) and locknut (20). Tighten locknut to 190 N-m (140 ft.-lbs.) torque.

Install idler shaft (34) and bearing assembly through rear of housing and drive it through idler gear (15). Install rear bearing cup (35) and end plate (46). Tighten bolts to 27 N-m (20 ft.-lbs.) torque. Drive front bearing (16) onto idler shaft (34) until seated. Install bearing cup (16) and end plate (3), Tighten bolts to 27 N - m (20 ft.-lbs.) torque and hit idler shaft (34) to seat bearings.
Mount dial indicator so end of probe contacts end of idler shaft (34—Fig. 16). Measure and record amount of end play. End play tolerance is 0-0.05 mm (0-0.002 inch) for new bearings and 0.05-0.10 mm (0.002-0.004 inch) for used bearings.
To determine correct shim (36) thickness, subtract 0.025 mm (0.001 inch) from dial indicator measurement if new bearings are used, or subtract 0.076 mm (0,003 inch) from dial indicator measurement if original bearings are reused. The result is the required thickness of shims needed to obtain desired end play.

Remove rear end plate (46) and install correct shim (36) thickness. Reinstall end plate (46) and tighten bolts to 27 N-m (20 ft.-lbs.) torque. Recheck end play and adjust shim thickness, if necessary, if not within required tolerance.
Install input shaft (12-Fig. 16) and bearing assembly through front of  housing (2) and input gear (13). Install bearing cup (14) and end plate (3). Tighten bolts to 27 N-m (10 ft.-lbs.) torque. Drive rear bearing (11) onto input shaft (12) until seated. Install hearing cup (11) and end plate (46). Tighten bolts to 27 N-m (20 ft.-lbs.) torque. Set end play in the same manner.