Checking and replacing the front centering guide (BMW 5 Series E28)

Examination

The front centering guide ensures the unique installation of the cardan shaft in relation to the transmission flange. The guide, which is pressed into a channel in the front of the cardan shaft, enters into contact 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 (indicated by the arrow).

To check the centering guide, loosen the nuts and bolts that secure the flexible coupling to the transmission flange, grasp the front end of the driveshaft and try to move it up and down, as well as sideways. The shaft should 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 guide. This cover may be bent or deformed during shaft removal. Damage to the cover does not affect the operation of the centering guide - do not confuse a defective cover with wear of the guide itself.

Replacement

1. Remove the driveshaft (see section Removal and installation the propeller shaft).



2. Fill the channel behind the centering guide with thick grease so that the grease is level with the lower edge of the guide. Insert a metal rod of suitable diameter into the guide (approximately 14 mm), cover the guide with a piece of rag and tap the rod with a hammer (don't try to use a rod of a smaller diameter - it won't work; the grease will be squeezed out from the sides). The increase in hydraulic pressure of the grease when the rod is immersed in it leads to the squeezing out of the centering guide from the cardan shaft.



3. Lubricate the new centering guide with molybdenum disulfide grease and press it into the drive shaft. Make sure that the insulating lip of the guide protrudes outward above the shaft surface by approximately 4.5 mm (dimension A).

4. Install the cardan shaft (see section Removal and installation the propeller shaft).