mipstien

I just picked up a running 04 a4 1.8 quattro avant. 163k miles. 5hp19 automatic 5 speed
I was told it needs a trans but the seller didn't provide much reason and didn't tell me he attempted any fixes.
When I put it into gear it feels like it engages and when I first give it fuel it tries to move and sometimes does so but only momentarily. At this point I can give it all the beans and it will move at about 5k rpm or more. It feels like it's slipping at this point. It will move on flat ground but if it gets an incline, like putting it on the back of a roll back, it begins to slip 100%. It had a few codes and I cleared them after putting in a new battery and charging the engine oil. They did not all come back but I only really let it warm up sitting as I'm not able to drive it any distance.
The research I've done says the tcu is not an uncommon problem if it got wet. I did check the drains and cleaned them. They happened to be very clogged.
I haven't checked the trans fluid yet because I just flat out forgot while doing the engine oil.
Could this be a tcu failure? Or maybe fluid problem? Lastly could it just be something in the trans and it's just shot, particularly clutch pack f iirc?
I don't have a vcds, but my tool can get diagnostic info. I can get more info if needed.


Full Vehicle System AI Inspection ReportThe Report is created by TOPDONSN:988975606779Test Time:04/02/2023 12:12Repair ShopMake:AUDIVIN:WAUVC68E04A124573Vehicle Software Version:V10.18Vehicle InformationInspection Result02 Transmission Electronics 1 problems exist1.P1750 Voltage Supply:Voltage Too Low03 Brake Electronics 2 problems exist1.01826 Steering Angle Sensor, Voltage SupplyTerminal 302.01119 Gear Recognition SignalThe following systems are OK:1.01 Engine Electronics2.15 Airbag

Cybersombosis

Couple things you can try. Does it move better when you have it in tiptronic? Second is if you unplug the TCU, it should go into safe mode and give you second and reverse. See what happens when you unplug it. A fluid check/top up would also be the first thing I would do before looking for a replacement trans or pulling and doing work to it.

mipstien

Tiptronic didn't appear to change anything. I finally got into the computer area today and unplugged the TCU and it also didn't go to second or reverse any better. I ordered a TCU but the one I received is different than the one I purchased and so is not the same as the one under the hood.
I suppose my next step is to change the oil and filter in the trans and see if any metal bits are in the oil.

mipstien

I went and did some more testing today. By looking at live information I was able to determine the torque converter never engages the clutch and if it does it doesn't appear long enough for the computer to refresh it. The gears show the same in the computer as they do on the dash and shifter. In this case it's only 1st and reverse. When I put it in D and take my foot off the break every few seconds it tries to lurch. I tested the other TCU just to see what happened and it gave a bunch of codes. Reinstalled original and codes went back to what they originally showed. I cleared them and again they did not come back on.
Is there any way to diagnose a torque converter in this case?

turbo510

I doubt the torque converter is the problem. Also, the TC clutch isn't involved unless the car is in a cruise condition, and a non-locking TC clutch won't affect how the car accelerates.

My guess is clutches are just worn out. Trying to make a car go by 'giving it the beans' while slipping just ensures that the plates are ruined, so either a rebuild or used, working trans is the solution, I'm afraid.

mipstien

I appreciate that info. It makes it easier to go ahead and start ordering parts. I am planning on finding a trans and tc to swap in. That was the original plan anyways.