Removing and installing mechatronic unit for dual clutch gearbox J743 with gearbox removed — AUDI

🧭 Before you start

Drain the oil, seal the breather, remove the input speed sender and lift the engaging levers off the plungers with the assembly lever, then unbolt and remove the mechatronic. Check each of the 4 selector forks, set them back to neutral, clean the sealing faces and fit the guide pins. Set the gear actuators on the unit to their specified positions, fit and bolt the unit, and remove the assembly lever slowly. Seat the plungers, refit the sender and breather cap, fill gear oil after the gearbox goes in and run the basic setting.

Fits: Audi A3 (8P, 2003–2012), Audi TT Mk2 (8J, 2006–2014), Audi A1 (8X, 2010–2018), Audi A3 (8V, 2012–2020); platform codes FV, 85

• Opens: engine oil, gearbox oil
• Special tools named: T10407
• Renewed: cap
• Also covered elsewhere: Workshop Manual "“7-speed dual clutch gearbox 0AM/0CW (S tronic)”":

Don't miss

• Discharge any static before touching the mechatronic unit.
• Never loosen the bolts on the mechatronic unit's own cover.
• Slide the assembly lever in only until its groove lines up with the housing rib, then turn it 90°.
• Remove the assembly lever slowly; a sudden lever drop triggers clutch self-adjustment that cannot be undone.
• All 4 selector forks must be back in neutral before the unit goes on.
• Run the basic setting in guided functions once the gearbox is installed.

Written for this job from the workshop steps below · TorqFix editorial.

📋 Procedure

1. Place drip tray, e.g. used oil collection and extraction unitV.A.G 1782 below gearbox.
2. Remove oil drain plug (arrow) from gearbox.
3. Allow oil to drain off, then retighten oil drain plug.
4. Remove cap from breather opening (arrow) and seal opening to prevent oil from escaping . [Note: There are different types of breather cap on different versions; renew cap if necessary.]
5. If fitted, remove cover above engaging levers.

6. Carefully pull gearbox input speed sender 3G641 out of gearbox (arrow). [Note: The following step is necessary in order to lift the two engaging levers of the dual clutch away from the plungers of the mechatronic unit. Otherwise, the levers will jam the mechatronic unit at the plungers and prevent it from being removed.]
7. Insert assembly lever T10407 below plungers (2) between gearbox housing and the two engaging levers (1)(arrow), as shown in illustration.
8. Only slide in assembly lever T10407 until groove on assembly lever is in line with rib on housing (arrows), as shown in illustration. Do not slide it in all the way. [Note: The back of the assembly lever must make contact with the gearbox housing.]
9. Now rotate assembly lever T10407 90° anti-clockwise about its own axis (arrow A) so as to lift engaging levers away from plungers (1)(arrow B).
10. If necessary, press the assembly lever T10407 against the gearbox housing with a screwdriver to prevent it from slipping out when it is turned. [Note: The assembly lever T10407 remains inserted between the engaging levers and the gearbox housing while removing and installing the mechatronic unit.If necessary, press the assembly lever T10407 against the gearbox housing.]
11. ⚠ Risk of irreparable damage to gearbox components.Before touching or removing the mechatronic unit for dual clutch gearbox J743, always discharge any static electricity by touching an earthed object with your hand.Never touch the contacts in the gearbox connector with your hands. Electrostatic discharge could cause irreparable damage to the control unit and, consequently, the mechatronic unit. — Touch a suitable earthed object with your hand (without gloves) to discharge any static electricity. [Note: Make sure that the screwdriver used to support the assembly lever T10407 does not jam against the mechatronic unit.] [Note: The mechatronic unit is returned for reconditioning complete with oil filling.]
12. ⚠ Risk of damage to mechatronic unit for dual clutch gearbox J743!Do not loosen bolts securing cover on mechatronic unit for dual clutch gearbox J743.Make sure that no oil escapes through the breather hole when placing down mechatronic unit for dual clutch gearbox J743 after removal.Oil that has escaped cannot be refilled! — Remove bolts (B) in diagonal sequence.
13. Remove bolts (A).
14. Detach mechatronic unit from gearbox. [Note: A new mechatronic unit is supplied with the correct oil filling.]
15. ⚠ Risk of damage to mechatronic unit for dual clutch gearbox J743.In some cases it may not be possible to remove the mechatronic unit.This can happen if the gear actuator at the top left of the mechatronic unit is stuck.Do not attempt to remove the mechatronic unit by force.The mechatronic unit must be first brought into the correct position for removal by hand . — Seal off breather opening of mechatronic unit with a cap from engine bung setVAS 6122 to prevent oil from escaping . [Note: There are different types of breather cap on different versions; renew cap if necessary.The new mechatronic unit is supplied with the protective cap fitted to seal it off.Make sure that all selector forks are in "“centre position”" before installing mechatronic unit for dual clutch gearbox J743."“Centre position”" is position (N) (neutral) in the illustration below.No gear is engaged in this position, the gearbox is in neutral.]
16. First check each of the 4 selector forks by hand.
17. Move the 4 selector forks once into each position (arrows), one after the other.
18. Then shift all selector forks back into »centre position«, position (N). [Note: Turn the relevant selector gears slightly to make it easier to move the selector forks.]
19. Clean sealing surface on which mechatronic unit is to be installed.
20. Screw in bolt guide pins T10406 hand-tight.
21. ⚠ Risk of damage to mechatronic unit for dual clutch gearbox J743.Do not apply any pressure to the sensors when levering out the plungers. — Adjust the four gear actuators on the reverse side of mechatronic unit for dual clutch gearbox J743 to the specified positions.
22. Clean sealing surface on mechatronic unit.
23. Put on mechatronic unit.
24. Tighten bolts for mechatronic unit .
25. ⚠ The clutches can be damaged.If the clutch engaging levers contact the clutch actuators of the mechatronic unit abruptly, this can move the actuators out of position and activate the clutch self-adjustment. The status prior to self-adjustment cannot be recovered. — Turn assembly lever T10407 slowly and carefully in clockwise direction and remove.
26. Pull out plungers by hand until they are seated correctly in retainers.
27. Install gearbox input speed sender 3G641 (direction of (arrow)).
28. Take care not to damage clip of sender.
29. If previously removed, install cover above engaging levers.
30. Remove sealing plug from breather opening of mechatronic unit and fit breather cap (arrow). [Note: If the mechatronic unit is being renewed, fit the sealing plug on the old mechatronic unit so it remains oil-tight when it is returned for reconditioning.Do not drain oil out of the old mechatronic unit.]
31. After installing gearbox, fill up gear oil. For instructions for "“Renewing gear oil”", refer to Workshop Manual "“7-speed dual clutch gearbox 0AM/0CW (S tronic)”": [Note: The gear oil level cannot be checked.The gear oil has to be completely drained and then refilled.]
32. After installing the gearbox, run the Basic setting complete function in Guided Functions.

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