By Frank Twarog
Beginning in 1969, Land Rovers were fitted with a single 2 speed wiper motor situated in the far left hand side of the dash assembly. When the switch is activated a series of gears rotate in order to drive a "piston" up and down inside the motor. This piston (the drive link) is connected to a long coil of metal resembling fusilli pasta (the drive cable). At each of the wipers there is a wheel box with a gear that the drive cable passes through. As the cable moves back and forth, the gear inside the wheel box rotates back and forth, the gear inside the wheel box rotates the shaft that the wiper arms attach to. At the factory, Grease was applied inside the motor, along the cable and at each of the wheel boxes. Over time, the grease dries and acts as a hindrance rather than as a lubricant. This can cause your wipers to act slower than necessary and will create an unpleasant "whine" from the motor.
To aid your wipers in working better you should begin by removing the wiper arms and then begin to gain access to the motor and connecting tubes. This is very easy in a IIA, as only 4 screws and a cosmetic plate need to be removed. It will take more time for owners of Series III, 90's and 110's, as the upper dash and lower left cover panel must be removed.
The motor is held in place by a securing strap. Only the upper screw needs to be removed. In order to remove the motor (there is a securing nut plate on the other side of the bulkhead - if both screws are removed , the plate will fall and cause distress and frustration during the reassembly process).
The drive cable is still attached at this point and will pull out from the wheel boxes. Use brake clean to de-grease the cable. Remove the four bolts and flat plate from the back side of the motor, exposing the drive link. Remove the circlip retaining the drive link to the plastic gear as well as the circlip that retains the gear to the wiper housing. Remove the 2 bolts that secure the worm gear and armature. Use brake clean to spray out the now wax-like grease from the gear,, drive link, housing and worm gear. Check the brushes and drive gears for excessive wear. Now, reassemble using the highest quality grease available. The best product we have found for this part is synthetic grease from permatex.
Now, turn attention to the wheel boxes. Two small bolts retain a plate to the face of the wheel box - remove these, the plate and the 3 tubes that house the drive cable. Now clean the wheel boxes and examine for wear - replace if necessary (if you have ever experienced "sloppy" wipers that over extend the wind screen during windy conditions, the wheel boxes are the likely culprit). New genuine wheel boxes now include the updated splined drum adapter. These adapters are an improvement over the earlier ones, as they affix themselves to a "D" shaped shaft which prevents them from loosening and sliding on the shaft. If you have early wheelboxes and want to replace your adapters with the upgrade, use a file and grind down the round shaft on one side. The shaft is 1/4" in diameter and needs to be filed flat to 3/16" - file 7/8" down the shaft in order to allow the adapter to seat at the proper depth.
Now, reassemble and grease the wheelboxes and drive cable - pass it though the tubes and put them into place. Fit the motor and reconnect the securing strap and wiring. Refit the wipers and test. Your wipers should now operate smoothly and the motor ought to be as quiet as when it left the factory.