OK the car, a 2000 a4 quattro 1.8t (ATW) with a tiptronic trans. the problem, well...

Neither my hand held scanner or my vag com (rosstech) can detect the TCU
The transmission itself will function perfectly in gear 1,2 and 3 but the second it goes into 4th or 5 the trans either slips or bogs and goes into limp mode and the revs fly but the car doesent accelerate, at that point all i can do is stop restart the car and hopefully operate it in the first 3 gears.

Amongst teh other problems it has this is the one thats really holding me back. so whats everyone thinking,
bad TCU, bad solenoids, clogged filter, bad torque converter, bad tranny altogether, or is the car just possessed by the devil.

 

Maybe a seized bearing on the 4-5 shaft? Just a guess, I've only ever worked on manuals. Same behavior in both auto and tip, I assume?

 

yep wether its in tip or auto the second its hits 4 hell breaks loose,

 

Start simple and change the fluid and filter. I'd say dump in a bottle of Lucas Transmission Fix but I doubt it's compatible with Audi/VW tranny oil.

 

Only thing about tranny fluid, besides having to fill at a certain temp, is you have to do it twice. The issue is after you change it the first time, the detergents can possibly break up all that gunk, and end up clogging your trans filter, stopping fluid flow, and making a bad situation worse.