Adjusting The Crown Wheel (Transmission G 86)

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Determining the total disc thickness "Stot." (S1 + S2).

Readjustment of the crown wheel is necessary if the transmission housing, the cover for the final drive, the tapered roller bearings for the differential, (the differential housing) or the drive set are replaced.

NOTE: The output shaft must be removed in order to determine the preload of the tapered roller bearings on the differential.

Remove the sealing rings and tapered roller bearing outer races for the differential and take out the adjusting shims.
Install the tapered roller bearing outer races without adjusting shims.
Put the differential without the speedometer-drive gear into the housing, put on the cover and tighten all screws with the stipulated tightening torque.
Fit the special tools 521/4 and 521/12.

Fig 1: Fitting The Special Tools 521/4 And 521/12
Courtesy of PORSCHE OF NORTH AMERICA, INC.
Place the special tool VW 385/17 onto the collar of the differential.
Secure the special tool VW 387 with the dial gauge and extension to the housing, and set to "0" with 1 mm preload.

Fig 2: Securing Special Tool And Dial Gauge
Courtesy of PORSCHE OF NORTH AMERICA, INC.
1. A Dial gauge extension, approx. 30...40 mm long
Move the differential up and down. Read off and note the play at the dial gauge. Example: 1.42 mm
NOTE: Do not turn the differential when measuring the play, otherwise the measurement result will be falsified.

Calculate "Stot.".

"Stot." = measurement result + pressing.

Example:

STOT MEASUREMENT CALCULATION

Measurement result		1.42 mm
Pressing (constant value)	+	0.50 mm
"Stot."	=	1.92 mm

Install the determined total disc thickness "Stot." behind the tapered roller bearing outer race in the transmission housing.
Measure the friction torque with a commercially available torque gauge (0...600 Ncm (0... 53 inlb.)). It must be 250...350 Ncm (22...31 inlb.) in the case of new tapered roller bearings and it must be 30...60 Ncm (2.6...5.3 inlb.) in the case of run-in tapered roller bearings (bearings filled with gear oil).

Fig 3: Measuring Friction Torque Using Torque Gauge
Courtesy of PORSCHE OF NORTH AMERICA, INC.

A Torque gauge

NOTE: When readjusting the drive set, also adjust the output shaft and perform a check. Refer to ADJUSTING THE OUTPUT SHAFT (TRANSMISSION G 86) .