Examination
The front centering guide ensures that the cardan shaft is uniquely positioned in relation to the transmission flange. The guide, which is pressed into a channel at the front of the driveshaft, engages with the guide pin on the transmission flange. Wear of the centering guide leads to vibrations in the front of the cardan shaft.
Sectional view of the centering guide (arrow).
To check the centering guide, give the nuts and bolts that secure the flexible coupling to the transmission flange, grab the front end of the driveshaft and try to move it up and down, as well as to the sides. The shaft must fit snugly on the transmission flange pin. If there is noticeable play, replace the shaft.
Some driveshafts are equipped with a dust cover at the front end that fits over the centering rail. This boot may be bent or deformed during shaft removal. Damage to the boot does not affect the operation of the centering guide - do not confuse a defect in the boot with wear on the guide itself.
Replacement
1. Remove the cardan shaft (see Section Removal and installation of cardan shaft).
2. Pack the channel behind the centering guide with grease until the grease is level with the bottom edge of the guide. Insert a metal rod of suitable diameter into the guide (approx. 14 mm), cover the guide with a piece of rag and tap the rod with a hammer (do not try to use a smaller diameter rod - it will not work; grease will squeeze out from the sides). An increase in the hydraulic pressure of the lubricant when the rod is immersed in it leads to the extrusion of the centering guide from the cardan shaft.
3. Lubricate the new centering guide with molybdenum disulphide grease and press it into the propeller shaft. Make sure that the insulating sponge of the guide protrudes outward from the surface of the shaft by about 4.5 mm (size A).
4. Install the cardan shaft (see Section Removal and installation of cardan shaft).