Speed transmission – power shift unit


OVERHAUL. To remove the Power Shift unit, speed gearbox must be removed from the tractor. To remove the speed gearbox, first remove cab and fuel tanks or fenders, tank and platform. Remove plugs and drain fluid from speed gearbox and rear frame. Remove front drive axle drive shaft and shield, if so equipped. Unbolt and remove pto clutch cover from bottom of rear main frame. Refer to Figure and drive out roll pin (1) from pto clutch and shaft. Unbolt lower pto shaft cover or seal housing, as equipped, and remove with gasket from rear of tractor. Have helper support the pto clutch. With-draw lower pto shaft and remove pto clutch. Remove the snap ring from rear of pto driven gear, then remove driven gear. Disconnect 1st-2nd and 3rd-4th selector rods from gear selector levers.

Disconnect all interfering hydraulic lines and wiring. Using a sling and hoist, lift off steering support assembly. Remove right and left brake pipes. Remove steering supply and return pipes, power shift return pipe and oil cooler supply and return pipes, Plug or cap all openings Immediately to prevent foreign material from entering systems.
Place special tool or equivalent, under tractor. Adjust splitting tool to support tractor under speed gearbox and rear main frame. Place wooden wedges between front axle and front support to prevent tipping. Unbolt range section (rear frame) from speed gearbox. After making certain that all wires and hydraulic lines are disconnected, roll engine and speed gearbox forward from range section.

Churchill tool number MS 2700 used tor splitting tractor

A. Guide rail, B. Movable support, C. Static support, D. Actuating crank

Attach a sling and hoist to speed gearbox and block up securely under engine oil pan. Unbolt clutch housing from engine, then separate speed gearbox from engine. If available, attach speed gearbox assembly in a tractor transmission stand.
Unbolt and remove bottom core plate (12) and regulator valve (4) assembly, then remove oil inlet tube (7). Remove clutch release bearing and sleeve. Drive roll pins from release fork, withdraw release shaft and remove fork. Unbolt and remove pto driven shaft end cover and metal gasket. Remove snap ring from front end of driven shaft. Working through bottom core plate opening, remove snap ring from pto driven gear. Drive the driven shaft rearward out of bearing and remove bearing. Withdraw the shaft and have helper remove gear as shaft is removed. Unbolt and remove clutch release sleeve carrier, then withdraw pto drive shaft and gear. Remove snap ring from front end of countershaft and remove countershaft gear. Remove the two speed Power Shift unit from front of speed gearbox.

To disassemble the removed Power Shift unit and proceed as follows: 
Clamp clutch shaft (28) in a soft jawed vise. Remove snap ring (7), then using a suitable puller, remove clutch assembly (8 through 19) and (33 through 37). Remove Woodruff key (29) from clutch shaft (28) and slide low drive gear (30) with Sprague clutch (31) and oil seal (32). Remove oil seal and sprague clutch with brass cup from low drive gear. Remove snap ring (26) and slide housing (21) from shaft. Unlock and remove the two seal rings (23), remove snap ring (24), press bearing (25) from shaft and remove thrust washer (27).

Place clutch assembly in a press and compress reduction side clutch plates, then remove retaining ring (33). Remove back plates (34 and 37) clutch discs (35) and separator plates (36). Turn clutch cup (16) over and pry out retaining ring (8). Remove back plates (9 and 12), clutch discs (10) and separator plates (11). Using an Allen wrench, remove pressure plate bolts (19) and nuts. Remove pressure plate (18), Belleville washers (17), piston (13) and three washers from clutch cup. Remove "O" rings (14 and 15) from piston.
Clean and inspect all parts and renew any showing excessive wear or other damage. When reassembling, use all new "O" rings, seal rings and oil seals and reverse disassembly procedure keeping the following points in mind: 

Before installing new friction discs (10 or 35), soak discs in clean Hy-Tran Plus fluid for three minutes. Using a micrometer, measure thickness of low clutch components; retaining ring (33), back plates (34 and 37), three friction discs (35), two separator plates (36) and pressure plate (18). Measure the stack in four places. The thickest measurement will be dimension "A". Correct thickness for dimension "A'" is 1.042-1.055 inches (26.466-26.797 mm). Refer to chart and select shim as required to obtain dimension "A". Shims are available in thicknesses of 0.014 inch (0.355 mm), 0.024 inch (0.609 mm) and 0.036 inch (0.914 mm).

Two speed Power Shift unit 

1.Needle bearing, 2.Direct drive gear, 3.Needle bearings (2), 4,Ball bearing, 5.Splined gear, 6.Snap ring piston, 7.Snap ring, 8.Retaining ring, 9.Clutch back plate, 10, Clutch discs (3), 11. Separator plates (3), 12.Piston back plate, 13.Direct drive, 14. "O" ring, 15. "O" ring, 16. Clutch cup, 17.Belleville washer, 18.Pressure plate, 19.Bolt (3), 20.Oil seal, 21.Housing, 22."O" ring, 23.Seal rings, 24. Snap ring, 25.Ball bearing, 26.Snap ring, 27. Thrust washer, 28. Clutch shaft (2), 29.Woodruff key, 30. Low drive gear, 31. Sprague clutch, 32. Oil seal, 33. Retaining ring, 34.Clutch back plate, 35.Clutch discs (3), 36.Separator plates, 37.Piston back plate, 38.Countershaft, 39.Snap ring, 40.Low driven gear, 41.Snap ring

Use petroleum jelly to stick the three washers in piston side of housing. Lubricate new "O" rings (14 and 15) on piston with petroleum jelly and install piston in clutch cup. Turn clutch cup (16) over and install the three Belleville washers (17) so concave side faces outward. Aligning the holes, install clutch pressure plate (18). Apply Loctite 270 on threads of bolts (19) and install bolts and new nuts. Tighten bolts to a torque of 5-6 ft.-lbs. (7-8 N-m). Use a center punch and stake the nuts. Install the predetermined shim, piston back plate (37), friction disc (35), separator plate (36), friction disc (35), separator plate (36), friction disc (35) and clutch back plate (34). Align notches in clutch friction discs, compress clutch plates and install retaining ring (33).

Chart used In selecting shim to adjust correct thickness of low clutch components

Turn clutch cup over and measure the distance from retaining ring groove to face of piston. Record as dimension  'A'. Using a micrometer, measure thickness of direct drive (high) clutch components; retaining ring (8), back plates (9 and 12), two separator plates (11) and three friction discs (10). Measure the stack in four places. The thickest measurement will be dimension "B". Subtract dimension "B" plus 0.035 inch (0.899 mm) from dimension "A". 

The result will be dimension "C". Refer to chart and select correct shim or shims as required to obtain a correct dimension "C" of 0-0.015 inch (0-0.381 mm). Install the predetermined shim, piston back plate (12), friction disc (10), separator plate (11), friction disc (10), separator plate (11), friction disc 10), clutch back plate (9) and retaining ring (8). Check to see that direct drive clutch plates are free to rotate and that minimum clearance between retaining ring (8) and back plate (9) is 0.030-0.040 inch (0.7624.016 mm). Place clutch in a press and compress Belleville washers until the direct drive clutch plates are just locked. Then, check to see that low clutch plates are free to rotate and that minimum clearance between retaining ring (33) and clutch back plate (34) is 0.030-0.040 inch (0.762-1.016 mm). If not, recheck shimming procedures.

Install sprague clutch (31) in low drive gear (30) and install the brass cup ring. Install oil seal (32) until seal is 0.050 inch (1.27 mm) below gear face. When low drive gear and sprague clutch assembly is installed on shaft, make certain that gear will rotate clockwise (viewed from front) and will lock to shaft in opposite direction. 
Reinstall speed gearbox to engine. Apply Loctite 515 gasket eliminator to mounting face of range section, then reconnect speed gearbox to range section. Tighten bolts securing speed gearbox to engine and speed gearbox to range section to a torque of 80 ft-lbs, (108 N-m).

Low drive gear and sprague clutch should rotate freely In clockwise direction (viewed from front) and lock to shaft when rotated in counterclockwise direction