Figure 4-20. Main Drive Gear - Exploded View


Assemble parts 4 through 8 to mainshaft before installing mainshaft in gear case. Position gear (8) on shaft splines. Press or fit ball bearing housing (7) over ball bearing (6) and press onto shaft. Assemble lockwasher (5) and nut (4) to shaft and tighten to 50-60 ft-lbs torque. Bend over one ear of lockwasher against flat of nut.

Insert mainshaft assembly into gear box far enough to install gear (10), thrust washer (11), lock ring (12) and shifter clutch (13) over shaft. Always install new lock rings and make sure they are properly seated in lock ring groove. One side of mainshaft shifter clutch is stamped "HIGH." Make sure this side faces main drive gear.

With a suitable tool, work lock ring onto shaft splines. Use tool wedged against shifter clutch to force lock ring into seat in shaft. Use care not to distort lock ring.

With a soft metal hammer or brass drift, tap mainshaft assembly into case until flange on ball bearing housing is shouldered against case. Install retaining plate (3), oil deflector (2) and four screws (1). Tighten screws to 6-9 ft-lbs torque.

If working on three-speed transmission, install reverse idler gear (31, Figure 4-18) and shaft before installing retaining plate.


Before installing countershaft gear train to shaft and case, it is necessary to check bearing fit and shaft end play.

If countershaft mounting collars (32 and 33) were removed for replacement, press or drive old parts out and new parts in after gear case has been heated to approximately 300 degrees to expand case and facilitate pressing.

On early 1976 and earlier models, install roller sets (18 and 22) in countershaft gear (25), holding them in place with a coat of grease. Be sure lock rings (20 and 24) and bearing retaining washers (19 and 23) are in place before installing bearings. Install bearing thrust washer (20) in its recess in left end of countershaft gear. Install countershaft temporarily to check bearing fit. See "Transmission Specifications" for tolerances.

On late 1976 and later models, install needle bearings (18A and 22A) in countershaft gear. Coat bearings with grease.

Install countershaft gear in case holding end play adjusting washer (9) in place with daub of heavy grease. Install countershaft.

Check end play with feeler gauge between end play adjusting washer and end of countershaft gear. Consult transmission specifications for tolerances. Increase or decrease end play as necessary by fitting end play adjusting washer of required thickness. Washers are available in thicknesses of .074, .078, .082, .085, .090, .095 and .100 in.

When correct gear end play has been established, remove countershaft and gear from case. Set aside adjusting washer until needed for assembly.

Install gear bushing (17), gear (16), thrust washer (15) and gear lock ring (14) on countershaft gear (25).

Install shifter clutch (13), thrust washer (12), gear bushing (11) and gear (10) on countershaft gear. Check to make sure all rollers are in place in gear.

Place end play adjusting washer (9) on end of countershaft gear, holding in position with daub of grease. Position assembly in case and insert countershaft (8) with O-ring (8A) and lock plate (7). Straight edge of lock plate fits against edge of bearing retaining plate (3, Figure 4-4). Install lockwasher (6) and nut (5). Tighten nut to 56-65 ft-lbs torque and bend over one ear of lockwasher against flat of nut.

Install gasket (29), drive unit (28), washer (27) and screw (26).

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