Vintage Tractor Engineer

Clutch stiffness is something which users soon complain about, particulary if there is a loader fitted to the tractor. Some models (eg. MF165) have a grease nipple on the release shaft, which would be the most obvious place to start. However, it is likely that the tractor will need to be split to access the clutch and make further investigations.

An often overlooked, yet most likely cause of clutch pedal stiffness is the condition of the clutch finger mechanism. Worn pivot pins and fixing screw heads can, and do, affect the fingers’ movement. Replacement of these parts can significantly ease the pressure required on the clutch pedal. The holes in the end of the fingers themselves (where the fixing screws fit through) are also likely to be worn and so replacement may be necessary. When these components are in need of replacement, one or more of the clutch fingers sometimes don’t fully release. This causes uneven pressure on the clutch plate which obviously affects the friction efficiency of the clutch.

The fingers must also be adjusted both correctly and evenly. If the release bearing does not contact all the fingers equally then an uneven release of the clutch mechanism can occur, causing jamming and thus stiffness back at the pedal. Adjustment of each of the fingers can be checked with a simple tool as shown in the diagram.

CLUTCH

As a tractor clutch is used, wear takes place naturally on the friction surfaces. This will affect the setting of the clutch pedal free-play which must periodically be corrected.

The clutch pedal on a Massey Ferguson 35 is adjusted correctly when there is 3/8 inch (double clutch) soft movement between the clutch pedal in rest position (up) and when the pedal begins to feel firmer when pressed. [3/4 inch for single clutch models]

Adjustment is accomplished by slackening the clutch pedal clamp bolt and turning the clutch release shaft in relation to the pedal. Re-tighten the bolt and then check the soft free-play. Re-adjust if necessary.

PTO CLUTCH

Once the clutch has been adjusted then the PTO clutch release studs can be checked/reset. Remove the access panel on the underside of the tractor clutch housing. Using feeler guages measure the gap between the adjusting stud head and the PTO clutch release mechanism. This measurement should be between 0.089 - 0.091 inches. To adjust the setting, slacken the lock nut, move adjusting stud, re-tighten lock nut and re-measure the gap. The photograph below clearly shows this - this tractor has been split.

There are three adjusting bolts spaced equally around the clutch to measure and adjust. The clutch can be turned using a lever through the access panel. Applying a dab of paint to each stud after adjustment is a good way to be sure that you have done each one.