A4 1.8T CVT problem, urgent advice needed!

[a4_jim]

My first post and unlucky it has to be one with a problem about my CVT.

I brought a 2004 A4 1.8T (non S line) and everything is fine with the car apart from the CVT "speed sensor". My mech tells me this part is not like the old B5 but actually encased inside the "automatic gearbox control unit" which lives inside the gearbox.

I understand the unit is submerged in ATF oil but how does it read the speed from the gearbox? Does the contorl unit have any mechanical parts attached to the outside that bad ATF oil could affect it?

I'm trying to weigh out the differences in buying a new control unit to trying my luck by changing the ATF oil. I read online that it maybe possible to fix this error code by just changeing the ATF oil. However, ATF oil isnt cheap at 65 pounds for 5lts required but could save me a small fortune. New control unit is 400 pounds + 65 ATF oil + 100 labour charges.

Does anyone have any idea on what the best course of action is? Whats the cost of a new control unit in HK? Model "J217" as garage quoted.

Billion thanks!

Jim
p.s.
Located in HK but originally from UK.

 

[Macduff]

If you try changing the gearbox oil first and that doesn't fix it can't the mechanic re-use the oil when they change the control unit? After all the oil will still be brand new when it comes out again.