Synchromesh transmission with shift selector levers - overhaul


View of 12-speed synchromesh transmission

1.Front input shaft, 2.Snap ring, 3.Rear bearing carrier, 4.Bearing, 5.Input gear, 6.Snap ring, 7."O" ring, 8.Seal, 9.High /low slow gear, 10.Bushing, 11.Snap ring, 12.Bearing, 13.Spacer, 14.Snap ring, 15.Range pinion, 16.Snap ring, 17.Rear input shaft, 18.Gear carrier, 19.Bushing, 20.Reverse idler gear, 21.Dowel pin, 22.Washer, 23.Bearing, 24.Shim, 25.Mounting boll, 26.Shim, 27.Bushing, 28.Rear end housing, 29.Tab washer, 30.Bolt, 31.Locknut, 32.Washer, 33.Bearing, 34.Shim, 35.Spacer, 36.Spacer, 37.Spacer, 38.Bearing pad, 39.Snap ring, 40.Synchronizer, 41.Second gear, 42.Splined washer, 43.Split rings, 44.Shim, 46.Locknut (used with from drive,  46.Tab washer (used with front drive), 47.Washer (used with front drive), 48.Snap ring, 49.Front end housing, 50.Locating plate, 51.Splined washer, 52.Third gear, 53.Front synchronizer gear, 54.Synchronizer spring, 55.Bearing pad, 56.First/reverse gear, 57.Retainer plate, 58.Bearing, 59.Pinion shaft, 60.Tab washer, 61.Idler shaft, 62.Thrust washer, 63.Bearing, 64.Spacer, 65.Idler gear, 66.Bearing, 67.Thrust washer, 68.Bearing, 69.Countershaft assy, 70.Bearing, 71.Shim, 72.Spacer bar

Remove mounting bolts from input shaft rear bearing carrier (3) and remove input shaft (1) assembly. Remove snap ring securing input shaft front bearing carrier, then slide carrier from shaft. Remove "O" ring and oil seal from front bearing carrier. Remove seal (8) and "O" ring (7) from input gear (5). Remove snap rings (2 and 6) and remove input gear and rear bearing carrier with bearing from input shaft.
Drive roll pins from shift forks. Cover detent holes in end housing to prevent detent balls and springs from flying out as shift rails are removed. Keep each shift rail assembly together as they are removed. Use a wooden wedge to lock differential assembly, then remove pinion shaft nut (31).
Pinion shaft nut has left-hand threads.
Remove four nuts from housing spacer rods, then withdraw front end housing (49). Remove high/low slow gear (9). Remove idler shaft retainer plate (50), then remove idler shaft (61) and idler gear (65). Remove remaining bearing cups from end housing as necessary.

End plates, shift rods and shift

1.Front end plate, 2.Top spacer bar, 3.Rear end plate, 4.Shim, 5.Bushing, 6.Mounting bolts, 7.Tab washer, 8.Differential cap bolt, 9.Bottom spacer bar, 10.2nd & 3rd shift rod, 11.2nd & 3rd selector, 12.1st & reverse selector, 13.1st & reverse shift fork, 14.1st & reverse shift rod, 15.Gear lock, 16.2nd & 3rd shift fork, 17.Shift fork, slow/normal, 18.Slow/normal shift rod, 19.Selector, 20.Roll pin, 21.Detent ball, 22.Detent spring, 23.Range shift rod, 24.Shifter fork, Hi-Lo, 25.Sleeve, 26.Steel ball, 27.Plunger, 28.Plunger, 29.Shim, 30.Safety start switch

Remove neutral start plungers (27 and 28) and detent balls (26) from rear housing. Remove first and reverse shift rod assembly and second and third shift rod assembly. Remove countershaft assembly (69) and rear input shaft (17) assembly.
Press front bearing (12) off rear input shaft (17). Remove spacer (13), snap ring (14) and range pinion gear (15). Press reverse idler gear carrier (18), idler gear (20) and bearing (23) together off rear input shaft. Use care not to lose dowel pin (21). Remove bushings (10 and 19) from input shaft and reverse idler gear if necessary.
Remove first and reverse gear shift fork from pinion shaft assembly. Remove spacer (35), shims (36), spacer (37), washer (51) and third gear (52) from pinion shaft (59), Remove the six bearing pads (38), then lift synchronizer (40) with shift fork off shaft. Remove front and rear synchronizer gears, second gear (41) and the six bearing pads (55). Remove splined washer (42) and split retainer ring (43). Remove first and reverse gear (56). Remove pinion shaft retainer plate (57) and shims (44). Remove pinion shaft (59) and press bearing (58) off shaft.

INSPECTION

Clean and inspect all parts. Examine bearings and bushings for wear or damage. If renewing a bearing, renew its respective mating cup. Gear teeth should be evenly marked along length of teeth. If gear teeth have been shaved or show irregular wear pattern, gear should be renewed along with its mating gear.
If shifting into second or third has been difficult, examine synchronizer friction surfaces and the synchronizer pads (38 and 55). Slight radial clearance (looseness) in synchronizer is normal and the pads should slide easily into their grooves without binding. No attempt should be made to disassemble synchronizer assembly as individual service parts are not available.


If jumping out of gear has been a problem and gears appear good, examine fit of detent balls in grooves of shifter rails. Shift rail grooves should have straight 60 degree sides and balls must be smooth with no pits, rust or flat spots. If necessary, grind bottom of groove, taking care not to damage sides, until detent ball has sufficient clearance at bottom of groove. Check detent spring length which should be 31.75 mm (1.250 inches).
Examine all thrust washers and spacers for excessive wear or damage and renew as necessary.
If pinion shaft, end housings, center housing, or pinion shaft bearings are renewed, pinion shaft protrusion must be set before transmission reassembly.

PINION SHAFT ASSEMBLY

With pinion shaft (59), bearing (58) and correct thickness of shims (44) in position, install retainer plate (57) and tighten retaining bolts to 40 N-m (30 ft.-lbs.) torque. Install first/reverse gear (56) with shift fork groove toward retainer plate (57). Install split rings (43) and spacer (42). Apply grease to the six bearing pads (55) and install pads in splines of pinion shaft (59).

Install: 
- second gear (41) on pinion shaft and bearing pads with gear side toward retainer plate (57). 
- rear synchronizer gear (not shown) with slotted side against second gear (41). 
- snap ring (39) and front synchronizer gear (53) with slotted side of gear away from snap ring (39). Make certain front and rear synchronizer splines (teeth) are aligned. Place shift fork in groove on synchronizer, then install synchronizer and shift fork together making certain shift fork slides easily on spacer bar. Apply grease to the six bearing pads (38) and install in splines of pinion shaft (59). 
- third gear (52) on pinion shaft and bearing pads with gear side towards threaded end of pinion shaft. 
- splined washer (51) and spacer (37). Do Not install shims (36) or spacer (35) at this time. Place first/reverse gear shift fork in groove of first/reverse gear (56).

REAR INPUT SHAFT ASSEMBLY

Press bushing (10) into rear input shaft (17). Press bushing (19) into reverse idler gear (20).
Install : 
- snap ring (16) in groove of rear input shaft at bushing carrier(18)end.
- bushing carrier (18) on rear input shaft (17) with largest outside diameter next to snap ring (16). Lubricate and install reverse idler gear (20). 
- dowel pin (21) if so equipped. 
- thrust washer (22) with flat side toward reverse idler gear. Heat rear bearing to 120°C (250°F) maximum, then install onto shaft.
- high/low range gear (15) with larger diameter gear on shaft first. 
- snap ring (14) and spacer (13). Heat front bearing (12) to 120°C (250°F) maximum, then install onto shaft.
- input shaft assembly in position on rear housing (28) minus shims (24). 
- front housing (49) and tighten spacer bar nuts to 95 N-m (70 ft.-lbs.) torque. Mount dial indicator on front housing so probe touches end of rear input shaft. Move shaft up and down and measure end play. Correct end play is 0.05-0,43 mm (0.002-0.017 inch). Remove front housing and the rear input shaft assembly. Assemble and install shims (24) as necessary in rear housing bearing bore to obtain correct end play. Reinstall rear input shaft assembly.

COUNTERSHAFT ASSEMBLY

Heat bearings (68 and 70) to 120°C (250°F) maximum before installing on countershaft (69). 
Install: 
- bearing cup in rear housing without shims (71). Position countershaft in rear end housing. 
- front housing and tighten spacer bar nuts to 95 N-m (70 ft.-lbs.) torque.
Mount a dial indicator on rear housing so probe contacts face of rear gear of countershaft. Move shaft up and down and measure end play. Specified end play is 0.05-0.10 mm (0.002-0.004 inch). Remove front end housing, countershaft and rear bearing cup. 
- shims (71) as necessary to provide desired end play, then reinstall bearing cup and countershaft.
- first/reverse and second/ third shift rail assemblies.

FRONT HOUSING ASSEMBLY

Install: 
- bearings (63 and 66) and spacer (64) into range idler gear (65). Bearing cages should be slightly below end surface of range idler gear when installed. 
- idler gear assembly with a thrust washer (62 and 67) at each end. 
- idler shaft (61) and secure with locating plate (50) and mounting bolt. Position high/low slow gear (9) in front housing with shift fork groove up. 
- front housing assembly onto transmission making certain rear input shaft goes through high/low slow gear. 
- new spacer rod nuts and tighten to 95 N-m (70 ft.-lbs.) torque.

PINION SHAFT END PLAY

Install: 
- original shim pack (36) removed during disassembly plus an additional 0.25 mm (0.010 inch) thick shim. 
- shoulder washer (35) with flat side against shims. 
- bearing cone, washer and nut on pinion shaft and tighten nut to 270 N-m (200 ft.-lbs.) torque. 
Position a dial indicator on front housing so probe contacts end of pinion shaft. Move pinion shaft up and down and measure end play. Remove nut and bearing, then reduce shim thickness as necessary to provide zero end play to 0.05 mm (0.002 inch) preload. Reassemble using a new nut and tighten nut to 270 N-m (200 ft.-lbs.) torque.

FRONT INPUT SHAFT ASSEMBLY

View of front Input shaft assembly

1."O" ring, 2.Support sleeve, 3.Snap ring, 4.Front input shaft, 5.Seal, 6.Snap ring, 7.Bearing, 8.Snap ring, 9.Rear bearing carrier, 10.Bearing, 11.Snap ring, 12.Input gear, 13.Snap ring, 14."O"ring, 15.Seal

Install: 
- new needle bearing (10), if removed, into retainer (9) using special tool or other suitable tool. 
- oil seal (5) in support sleeve (2) and place "O" ring (1) on sleeve. Place input gear (12) onto shaft.
- snap ring (13).  
- new "O" ring (14) and oil seal (15) into input gear. 
- snap ring (11) against input gear. Slide rear bearing carrier assembly (9) onto input shaft. 
- front carrier bearing (7) and retaining rings onto shaft. Lubricate support sleeve seal, then slide sleeve over the shaft and onto front bearing. 
- snap ring (3) in support sleeve.

SHIFT RODS AND DETENT ASSEMBLY

Springs and aid for Installing detent balls end fabricate  a  tool using  the  following dimensions

A - 9,5 mm (0.375 inch), B - 15,8 mm (0.625 inch), C - 4,8 mm (0,187 inch), D - 150 mm (6.0 inch)

To facilitate installation of detent balls and springs, fabricate an installation tool as shown in Figure. Install detent ball and spring for first/reverse shift rod using tool. Push detent ball down with tool while moving shift rod into rod bore as shown.

When Installing shift rods and detents, use tool shown to push detent ball and spring

Install: 
- shift interlock plug by placing in position through second/third gear shift rod bore. With interlock plug in position, install detent ball and spring and second/third shift rod.
- remaining shift rods, forks, detent springs and balls in similar manner. 
- roll pins in shift forks and rods. Install neutral start switch balls, rods, plate and switch.
- input shaft assembly and tighten rear bearing retainer mounting bolts to 23-27 N-m (17-20 ft.-lbs.) torque.
Shift transmission and range section through all gears and check to be certain all gears and detents work properly.