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1998 vw T4 2.8 vr6 transmission


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  • 3 weeks later...

A fluid change is unlikely to fix a missing gear.

 

Assuming its a 01M transmission this is how it works.

 

You move the selector lever which rotates an actuator rod in the gearbox. For reverse and park the rod does mechanical interlock type stuff.

For the forward gears, cam faces machined on the rod act on the multifunction switch (MFS) which is a big white thing on the rear side of the gearbox facing the firewall.

This generates a 2 or 3 bit code on individual wires which are sent to the gearbox computer. This is located under the rear seat on a Golf but could be anywhere on a T4.

The gearbox computer then controls the solenoids in the gearbox to select the correct ratios. Again the solenoid signals are sent on individual wires to a multiway connector on the top of the gearbox.

 

The solenoids inside the gearbox are connected to this external connector using a flexi circuit, all of which sit in the gearbox oil.

 

Its commonly reported for a solenoid or the flexi circuit (flimsy connectors to the solenoid) to have failed. You can check the continuity from the gearbox computer plug using a meter, with the wiring diagram from the repair manual. The solenoids have specific coil resistances. You can also check all of this with VagCom.

 

Alternatively one of the outputs from the MFS could be short circuited to 0V or broken, or the switch itself could be faulty.

 

If the solenoids or flexi circuit need repair then access is via the sump, so you will need to change the fluid and filter anyway. The MFS is above the oil level so can be removed when the engine is not running. The MFS is retained by a clamp held on by a single bolt.

 

Although the gearbox ECU has a CAN connection to the engine ECU, the connection to the gearbox is entirely discrete, and uses lots of wires.

Problems with any one of these can cause strange problems which a new gearbox or gearbox computer will not cure.

Most people give up, but your problem sounds fixable.

 

Good luck.

Cheers Pete

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