Torsional Backlash, Measuring

• Pinion is installed with shims "S₃ " and "S₄ ". Refer to PINION, REMOVING AND INSTALLING .
• The output gear of the spur gear unit as well as the parking lock gear are removed. Refer to Fig 3.
• O-ring is inserted in final drive cover.

-- Install the differential with shim: "S ₁ *" is on the cover side, "S ₂ *" is installed in the transmission housing.

-- Install the final drive cover and tighten the four bolts to 20 Nm.

-- Complete the Crown Wheel Adjusting Tool: VW 521  (refer to Complete the Crown Wheel Adjusting Tool -VW 521- as follows: ) and insert it in the differential.

-- Turn the differential five turns in both directions so that the bearings settle.

-- Attach the Dial Gauge Holder: VW 387  -6- to the final drive cover -arrow-

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1. Dial Indicator: VAS 6080A 
2. Dial Gauge Extension (8 cm plan)
3. Measuring Lever: VW388 
4. Ring Gear Locking Sleeve: VW521/4 
5. Positioning Tolerance Shell: VW521/13 
6. Dial Indicator Holder: VW 387 

-- Insert the Dial Gauge for example: VAS 6080A  using the Dial Gauge Extension (8 cm (3.15 in.) plan).

-- Adjust the Measuring Lever: VW 388  to the dimension -a- = 79 mm (3.11 in.) (for the ring gear 196 mm (7.72 in.)).

So that an exact torsional backlash can be measured, the pinion must be locked.

-- To do so remove the bolt -1-.

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-- Place on the threaded hole washer or with a nut (for example M12) -2-.

• The dimension -a- must be at least 14 mm (0.55 in.).

Locking the pinion 1

2 -  M8 x 110 Bolt or M8 x 130 Threaded Rod with M8 Nut

3 -  Clamping Piece: VW386A 

-- Lock the pinion -1- with the bolt -arrow- from the Clamping Piece: VW 386A  .

Determine the play between the tooth flanks as follows:

-- Turn ring gear until it makes contact with a tooth flank (end of backlash travel).

-- Set the dial gauge to "0" with 2 mm pretension.

-- Turn ring gear back until lying against an opposite tooth flank (backlash).

-- Read the torsional backlash and write down the measured value.

-- Turn the ring gear 90° and repeat measurements three more times. Loosen the Clamping Piece: VW 386A  to additionally tighten.

Average Torsional Backlash, Determining 

-- Add the four measured values and then divide the total by 4.

Example:
	1. Measured value	0.55 mm
+	2. Measured value	0.54 mm
+	3. Measured value	0.55 mm
+	4. Measured value	0.56 mm
=	Total of the measured values	2.20 mm

• Results: the average torsional backlash is approximately 2.20 mm: 4 = 0.5 mm

Shim Thickness "S₂ ", Determining

Formula: "S₂ " = "S₂ *" - measured torsional backlash + specified torsional backlash

Example:
	Old shim "S 2 *"	1.17 mm
-	Measured average torsional backlash	0.55 mm
+	Specified torsional backlash (desired average value for the torsional backlash)	0.15 mm
=	Shim thickness "S 2 "	0.77 mm

Determine the shim according to the table. Refer to the Parts Information for the part number.