Forward-reverse transmission


Tractors may be equipped with a Forward-Reverse shuttle transmission located in front of the speed transmission. The Forward-Reverse unit is controlled by a lever on left side of instrument panel. This lever is linked to the hydraulic spool in the Forward-Reverse clutch housing. Movement of this lever engages one clutch and releases the other. To prevent damage to transmission, control lever cannot be moved until engine clutch release pedal is depressed. The range transmission, on models equipped with the Forward-Reverse unit, does not have a reverse; only a high and low. This gives the tractor a total of eight forward speeds and eight reverse speeds.


Some of the problems which may occur during operating of the Forward-Reverse transmission and their possible causes are as follows:
No drive through Forward-Reverse transmission. 
Could be caused by:
Mechanical linkage disconnected.
Low oil pressure.
Regulator valve stuck open.
Slipping Forward-Reverse clutches. Could be caused by:
Faulty regulator  valve.
Damaged piston "O" ring seals.
Damaged or excessively worn clutch plates.


OVERHAUL. To remove the bottom core plate (8) and regulator valve (2), first remove drain plug and drain transmission fluid. Disconnect battery cables.
Bottom core plate and regulator assembly can be removed without removing the speed gearbox. All other service on the Forward-Reverse transmission requires removal of complete speed gearbox.

Regulator valve and bottom core plate and relative components used on models equipped with Forward-Reverse

1.Plug, 2.Regulator valve, 3."O" rings, 4.Pressure tube, 5.Oil inlet tube, 6.Plug, 7.Plug, 8.Bottom core plate, 9.Gasket, 10.Separator plate, 11.Gasket

On models equipped with front drive axle, unbolt and remove drive shaft shield and front drive shaft. Then, on all models, unbolt and remove bottom core plate and regulator assembly. Remove inlet tube (5). Pressure tubes (4) will remain in speed gearbox.

Remove plug (1) with "O" ring (2), shim (3), pin (4), spring (5) and valve (6). Remove plug (9) and "0" ring (8). Unbolt and remove regulator valve body (7), then remove gasket (11), separator plate (10) and gasket (9) from core plate (8).

Regulator valve assembly.

1.Plug, 2."O" ring, 3.Shim, 4.Pin, 5.Spring, 6.Valve, 7.Body, 8."O" ring, 9.Plug

Clean and inspect all parts for excessive wear or other damage and renew as necessary. Valve body (7) is not serviced separately. Spring (5) should have a free length of 1.86 inch (47.4 mm). Use new gaskets and "O" rings and reassemble and reinstall by reversing disassembly and removal procedures.

PRESSURE TEST AND ADJUST. To check the oil pressure to the clutches, remove plug from test port in bottom of the regulator valve core plate. Connect a hose and a 0-500 psi (0-3500 kPa) test gage to the port. Warm transmission oil in tractor to a temperature of at least 100° F (38° C). Then, with engine operating at low idle speed, move control lever to select forward direction. Record pressure gage reading. Move control to select reverse direction and record gage reading. Stop engine. Pressure readings in both forward and reverse must be 300-320 psi (2070-2210 kPa). A low reading for one direction only would indicate damaged piston seal rings for that clutch. If readings are low in both forward and reverse, add shims (3) in regulator as required. Adding one shim will increase pressure by 20-30 psi (138-207 kPa). If a total of more than four shims are required, renew spring (5).