Specifications, Service and Repair of Farm and Lawn Tractors


Forward-reverse transmission of Case IH 685, 885 Tractor - Forward-reverse unit


To remove the Forward-Reverse unit, speed gearbox must be removed from Case 385, 485, 585, 685, 885 tractors, 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.

Drive roll pin 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. Unbolt and remove bottom core plate and regulator valve. Remove oil inlet tube from Forward-Reverse clutch housing.

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 and oil cooler supply and return pipes.

Plug or cap all openings immediately to prevent foreign material from entering systems. Disconnect and remove the Case 685, 885 Forward-Reverse lockout mechanism from speed selector cover.

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 assembly 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 assembly in a transmission stand.

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 as shown in Figure.

Remove snap ring from front end of pto 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 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. Remove snap ring from front end of countershaft and remove the reverse gear from countershaft.

Drive expansion plug from front of speed gearbox. Drive out the two roll pins from reverse idler shaft. Install a 1/4 x 8 inch NC bolt through the expansion plug hole and into reverse idler shaft.

Pull out the idler shaft and remove the reverse idler gear.

Unpin the Forward-Reverse actuating lever from speed selector cover, then turn lever clockwise to disengage lever from spool valve. Remove speed selector cover, selector shafts and forks.

Remove the Forward-Reverse unit from front of speed gearbox. Remove pressure tubes and "O" rings (3).

Fig.3. Case 685, 885 Forward-Reverse transmission. Item (25 through 31) are located in speed gearbox

1.Snap ring, 2.Washer, 3.Needle hearing, 4.Idler gear, 5.Washer, 6.Sleeve, 7.Roll pin, 8.Snap ring, 9.Shaft, 10.Roll pin, 11.Oil seal, 12.Pto shaft seal, 13.Clutch shaft seal, 14."O" ring, 15.Retaining ring, 16.Collar, 17.Forward-reverse shift spool, 18.Housing, 19."O" ring, 20.Seal rings, 21.Retaining ring, 22.Ball bearing, 23.Snap ring, 24.Thrust washer, 25.Needle bearing, 26.Forward drive gear & hub, 27.Needle bearings, 28.Ball bearing, 29.Clutch disc carrier, 30.Snap ring, 31.Retaining ring, 32.Retaining ring, 33.Oil deflector, 34.Clutch assy, 35.Drive gear, 36.Woodruff key, 37.Clutch shaft, 38.Snap ring, 39.Countershaft reverse gear, 40.Snap ring, 41.Countershaft

To disassemble the removed Forward-Reverse unit and proceed as follows: Clamp clutch shaft (37) in a soft jawed vise and remove shift spool (17) from housing (18).

Remove retaining ring (32) and oil deflector (33). Using a suitable puller, remove Forward-Reverse clutch unit (34).

Remove Woodruff key (36), then remove drive gear (35). Remove snap ring (23) and slide housing (18) from clutch shaft.

Unlock and remove the three seal rings (20) and remove retaining ring (21). Press shaft from bearing (32) and remove thrust washer (24).

Fig.4. Case IH 685, 885 tractor Forward-Reverse clutches

1.Retaining ring, 2.Clutch back plate, 3.Friction disc (4), 4.Separator plates (3), 5.Piston back plate, 6.Shim, 7.Piston, 8.Nut (3), 9,"O" ring, 10."O" ring, 11.Clutch cup, 12."O" ring, 13."O" ring, 14.Piston, 15.Spacer (3), 16.Bolt (3), 17,Shim, 18.Piston back plate, 19.Separator plates (3), 20,Friction discs, 21.Clutch back plate, 22.Retaining ring

To disassemble the clutch unit (34), place unit in a press (either end up) and apply pressure to clutch plates, then remove retaining ring (1).

Remove clutch back plate (2), friction discs (3), separator plates (4), piston back plate (5) and shim (6). Turn clutch cup (11) over and compress clutch plates, then remove retaining ring (22).

Remove clutch back plate (21), friction discs (20), separator plates (19), piston back plate (18) and shim (17). Using an Allen wrench, remove bolts (16) and nuts (8).

Bump clutch cup (11) on a bench and remove piston (7) and spacers (15). Turn clutch cup over and bump out piston (14). Remove "O" rings (9, 10, 12 and 13) from pistons.

Clean and inspect all parts and renew any showing excessive wear or other damage. When reassembling, use all new "O" rings, seal rings, gaskets and oil seals.

Before installing any new friction discs (3 or 20), soak new discs in clean Hy-Tran Plus fluid for three minutes.

When installing pistons, tighten new bolts (16) and nuts (8) to a torque of 6 ft.-lbs. (8 N-m), then stake the nuts. Reassemble clutches in clutch cup but install one 0.024 inch (0.61 mm) shim (6).

Do not install any shim (17) at this time. Install clutch assembly in a press with the side with shim (6) at the top.

Apply a load of 22-30 lbs. (98-133 N) and using a feeler gage, measure the clearance between clutch back plate (2) and retaining ring (1).

Clearance should be between 0.044 and 0.060 inch (1.117 to 1.524 mm). If the clearance is greater than 0.060 inch (1.524 mm), slums must be added.

If clearance measures less than 0.044 inch (1.117 mm), a thinner shim must be installed. When correct clearance is obtained, remove and measure thickness of shim and divide by 2, equally as possible.

For example, if shim measures 0.024 inch (0.61 mm), install one 0.014 inch (0.355 mm) thick shim on each clutch half. Shims are available in thicknesses of 0.014, 0.024 and 0.036 inch (0.355, 0.61 and 0.914 mm).

Reassemble and reinstall Forward-Reverse transmission by reversing the disassemble and removal procedures, keeping the following points in mind: Apply Loctite 515 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 ftlbs. (108 Nm).