Synchromesh speed transmission


The synchromesh speed tractor transmission used on models, is located in the rear portion of the clutch housing (speed gearbox). On tractor models equipped with the two speed Power Shift or Forward-Reverse transmission, speed transmission is directly behind them. 

The tractor speed transmission is equipped with synchronizers and therefore can be shifted with the tractor in motion by disengaging the clutch and applying a steady and continuous pressure to the speed shift lever until the shift is complete. The speed gearbox must be removed for all service on the speed transmission.

The four speed synchromesh speed transmission in conjunction with range transmission and without the Power Shift or Forward-Reverse transmissions, provides eight forward and four reverse speeds.

OVERHAUL

To remove the speed gearbox, first remove cab and fuel tanks or fenders, tank, platform and tunnel cover. Remove drain plugs and drain fluid from speed gearbox and rear frame. If so equipped, remove front drive axle drive shaft and shield. Unbolt and remove pto clutch cover from bottom of rear main frame. 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. Withdraw lower pto shaft and remove pto clutch. Remove snap ring from rear of pto driven gear, then remove driven gear. Disconnect all interfering hydraulic lines and electrical wiring. Then, using a sling and hoist, lift, off steering support assembly. Disconnect lst-2nd and 3rd-4th selector rods from gear selector levers. Remove right and left brake pipes. Remove steering supply and return pipes and oil cooler supply and return pipes.

Cap or plug 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.

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 to a transmission stand.

Speed gearbox cover and relative components

1.Expansion plugs, 2.Cover, 3."O" ring, 4.Brake return adaptor, 5."O" ring, 6.Housing, 7.Interlock pivot, 8.Shift lever (1st-2nd), 9.Housing, 10."O" ring, 11.Lube hose, 12.Shift lever (3rd-4th), 13.Housing, 14."O" ring, 15."O" ring, 16.Lube tube, 17."O" ring, 18.Snap ring, 19,Gasket, 20.Snap ring

To disassemble the removed synchromesh speed transmission, first remove the speed gearbox cover (2) as follows: 
Disconnect brake return hose from adaptor (4) and lube hose (11) from lube tube (16). Remove snap ring (18) from lube tube (16). Make certain shift levers (8 and 12) are in neutral position, then unbolt and remove cover (2). Remove lube tube (16) from gearbox. Disassemble of the cover and shift levers is obvious after examination of the unit and reference to Figures. 

To remove shift forks (28 and 29), remove snap rings (27) from grooves in shift rail (31). Drive roll pin (30) from the rail. Push the shift rail forward and rotate rail about 1/2 turn to unseat detent balls from slots in rail. Move snap rings rearward on rail and continue moving rail forward. Cover shift fork (28) with a shop towel to prevent losing detent ball (24) and spring (25). Lift out shift fork (28). Remove shift fork (29) in same manner.

Shift levers, shift forks and Interlocks used on synchromesh speed transmission

5."O" ring, 6.Housing, 7.Interlock pivot, 8.Shift lever (lst-2nd), 9.Housing, 10.'O" ring, 12.Shift lever (3rd-4th), 13.Housing, 14."O" ring, 21.Interlock, 22.Shift arm, 23.Nuts, 24.Detent balls, 25.Detent springs, 26.Dowel pins, 27.Snap rings, 28.Shift fork (1st-2nd), 29.Shift fork (3rd-4th), 30.Roll pin, 31.Shift rail, 32.Shift arm, 33.Spacer, 34.Interlock support arm, 35.Interlock

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 pto driven shaft. Working through bottom cover opening, remove snap ring from pto driven gear. Using a brass drift, drive the driven shaft rearward out of bearing and remove bearing. Withdraw the driven shaft and have helper remove gear as shaft is removed. Unbolt and remove clutch release sleeve carrier, then withdraw pto drive shaft and gear.

Before removing the main shaft (3), use a dial indicator and check end float between rear thrust washer (14) and second speed gear (13). End float must be 0.004-0.037 inch (0.102-0.94 mm). Then, measure end float between front thrust washer (14) and fourth speed gear (16). End float must be 0,0-0.076 inch (0.0-1.93 mm), if end float is excessive, new thrust washers must be installed during reassembly. Thrust washers are available in one size only.

Unbolt bearing cage (7) and slide main shaft (3), rearward far enough for access to snap ring (15). Separate thrust washers (14) and remove snap ring (15). Withdraw the mainshaft assembly (1 through 9) and remove thrust washers (14), second speed gear (13), synchronizer (12), hub (11) and first speed gear (10) as shaft is removed. Remove fourth speed gear (16), hub (17) and synchronizer (18). Remove spacer (9) from mainshaft. Remove snap ring (4), then remove main shaft and bearing (5) from bearing cage (7). Remove seal rings (8) and snap ring (6), then press bearing (5) from mainshaft. If desired, remove snap ring (1) and needle bearing (2). Remove housing (27) with "O" ring (28) and bushing (29) from front of speed gearbox. Remove transmission input (clutch) shaft (31) and bearing (30) out through rear of speed gearbox. Press bearing from shaft.

Synchromesh speed transmission gears and shafts

1.Snap ring, 2.Needle bearing, 3.Mainshaft, 4.Snap ring, 5.Bearing, 6.Snap ring, 7.Bearing cage, 8.Seal rings, 9.Spacer, 10.1st speed gear, 11.Hub, 12.Synchronizer, 13.2nd speed gear, 14.Thrust washers, 15.Snap ring, 16.4th speed gear, 17.Hub, 18,Synchronizer, 19.Needle bearing, 20.Oil seal, 21."O" ring, 22.Snap ring, 23.Bearing, 24.Pto drive shaft, 25.Oil seal, 26.Oil seal, 27.Housing, 28."O" ring, 29.Bushing, 30.Bearing, 31.Clutch shaft, 32.Snap ring, 33.Snap ring, 34.Bearing, 36.Snap ring, 36.Countershaft, 37.1st gear, 38.2nd gear, 39.4th gear, 40.Constant mesh gear, 41.Snap ring, 42.Needle bearing, 43.Cover, 44.Metal gasket, 45.Snap ring, 46.Bearing, 47.Pto driven gear, 48.Pto driven shaft


To remove the countershaft (36), remove snap ring (41) from groove in shaft. Remove snap ring (32), then using a brass drift, drive countershaft rearward. Remove snap ring (41) and gears (37, 38, 39 and 40) as shaft is withdrawn. Remove snap ring (33) and press bearing (34) from countershaft. Remove needle bearing (42) from gearbox.
Clean and inspect all parts and renew any showing excessive wear or other damage. Check synchronizer friction faces and cups for excessive wear or other damage. Press down on synchronizer ring, then release, to check centering action of springs. Synchronizers are serviced only as complete assemblies.

When reassembling, use all new "O" rings, seal rings, oil seals and gaskets and reverse disassemble procedures. When installing countershaft needle bearing, refer to Figure and install at distance shown. Apply Loctite 515 to mounting surface of range section, then reconnect speed gearbox to range section. Tighten retaining bolts to a torque of 80 ft.-lbs, (108 N-m). Refill transmission to level on dipstick with new Hy-Tran Plus fluid.
Install countershaft needle bearing (42) and pto ball bearing (46) as shown.