mike sharples

What symptoms does the torq converter give when failing?...My Allroad has developed a shudder under hard acceleration, there feels like a delay when setting off from a standstill, or when coasting and then going to load, this delay,also has a faint thud, happens intermittently, worse sometimes than other. No codes. Recently changed fluid and filter, shifting much cleaner and smoother but the intermitant thud and delay is getting worse. If this is the torq converter, is there an upgraded one, where is best place to get one from?

Prospeeder

well acceleration vibration which is what it sounds like, drive axles or drive line.

GTA_Driver

I would do another oil change, you could hve dirty oil still interfering with the valve body.

If the TC actually need replacing, get one from 517 Transmission. It's about $700-$800.

GTA_Driver

I had vibration under moderate acceleration and it was just dirty tranny oil. An oil and filter change fixed it. I also thought the TC was failing, drove like that for several years.

Edit: that was on my 2001 A6 4.2 with 5HP24 transmission.

Prospeeder

I have actually had changing the fluid make the engine light for the TC stay away for quite awhile, stayed off for like 6 months, then came back, and came back every week then. Fluid change didnt help. Really just a seal fails and causes the converter not to lock, if your hard accelerating, there not going to be any reason for converter lockup to be activated. hmmm... maybe with your trans the clutches were slipping or glazed and new fluid restored the friction modifiers and smoothed it out.

GTA_Driver

I had no issues with TC lockup. There were no codes. I am still leaning toward dirty oil not working well with the valve body, but who knows, I'm not a transmission mechanic.

The transmission mechanic did allude that the clutches could work better with the new fluid, but with the shavings that were in the filter, he also said it could intefere with the valve operation.

Prospeeder

Yours is chipped too right? Lot more power going through that auto trans. What intervals have you decided to change the fluid at?

GTA_Driver

That was my 2001 4.2 A6, not chipped or modified in any way except coilovers and wheels. It had the supposedly stronger 5Hp24 tranny, same as RS6.

Changed the fluid at 120K miles, took away the vibration, then drove it for 2 years and another 20K miles before the car got hit and was written off.

My Allroad is chipped, for one year and 12K miles so far. No issues with the transmission yet. I drive spiritedly but not abusively (whatever that means). It has the standard 5Hp19 tranny which is weaker on paper. Changed the oil already. It should have the upgraded TC from the factory.

jjrichar

With regard to the original problem, you may want to check the torsen diff fluid level. We had pretty much the same symptoms as you. Shuddering under acceleration that was completely removed by a fluid/filter change, but it still had a thud when transitioning from deceleration to acceleration. The shuddering I assumed the was from clutch pack or TCC slippage, which was corrected by the fluid change.

I found I had a leak from the output shaft from the transmission, which holds in the torsen diff fluid. Only way to check is to pump fluid into the fill hole until it overflows. Fluid is separate from the transmission, and takes 75W-90 synthetic gear oil. If it is this, you will need to replace the output shaft seal. It's pretty obvious if you have a leak as you will see it dripping from the heat shield below the output shaft.

mike sharples

I have a small leak from there,I have changed the oil in both diffs and the torsen diff,I used amsol synthetic 75/90...the leak is very small,something I will fix in the future,but the level is ok,am leaning towards dirty tranny fluid.I recently changed the oil and filter,the oil came out black,oil pan was sludgey,but no metal particles.I used the correct fluid,looks like apple juice,so,considering the original oil was so dirty,am going to change it again.The thud seems to be intermittent,yesterday I was coasting through local supermarket car park,gentle on/off the throttle,and I can feel the thud every time,it seems the more violent the throttle is used the harder the thud,gentle or very slow use,and theres no thud,making me think there is some excessive play somewhere in the drive train.When I do the tranny flush I will try to check out drive shafts etc...