Occasionally, my 2000 A8 feels like it's going over a rumble strip during acceleration. As soon as I back-off, the rumble stops. Then if I accelerate more slowly, it does not return. But if I get back on it as hard as was previously accelerating, the rumble returns.

This is happening more frequently.

Do you think this is a problem with the Quattro system? Perhaps I'm low on differential fluid. Or could there be something wrong with the viscous coupling? Or is this a transmission issue?

 

I now think it is a transmission problem. I think the trans is slipping in 3rd gear, especially when accelerating uphill, and when approaching the shift to 4th gear. Have you experienced this problem? What's really happening and what is the fix?

 

A relative thinks it might be the sparkplugs. Apparently, this happens in certain Fords. The plugs misfire and it feels like the trans is slipping. Sounds far-fetched to me. What do you think?

 

You would have the MIL on and/or DTC's showing in VCDS if this were the case.
I doubt it.... possible but unlikely.

 

It could be a number of things that cause what you are experiencing. Without a scan of fault codes its difficult to pinpoint. It could be plugs, coil pack, compression, icm, vacuum leaks. help us help you and give us a fault code to work with.

 

The Check Engine Light is not ON. I found this March 12, 2007 post on Edmunds from a guy by the name of estreed (http://townhall-talk.edmunds.com/dir...ee9e503/1361):

"I have worked on and rebuilt many of these A8 quattro units(5HP24A). They are a very heavy duty unit. The size of the gear train is about like a 3/4 ton truck. I have never seen a gear train failure yet. One quirk with this transmission is that Audi constantly slips the torque converter intentionally about 20 to 60 RPM for drive ability purposes, so it doesn't feel like the engine is getting lugged down. The side effect of this is that the torque converters wear out and when you try to do a light acceleration the engine rpms will constantly bounce about 300 RPM's. The reason for this is that the lining is worn off the torque converter. I've tried to change the transmission computers in several cars and it didn't fix a thing. I also checked the throttle position sensor and it was ok. Many times there will be no trouble codes in the transmission computer. VAG-com software is great but it can't do more than Audi's computers allow it to do. Many times there are problems that drive you crazy but the computer says everything is ok and from what the computer sees everything is ok because it's within tolerance. There is one valve that sometimes also sticks in the valve body from all this clutch material going through it. There are couple things to really be careful when changing the torque converter. It is very difficult to find a high quality converter since they are a very difficult converter to rebuild due to the design. Sometimes you can lose reverse with this trans as well. The most common reason is a piston blowing out in the very back of the trans and you pretty much have the rebuild trans when this happens.

Be very careful who rebuilds this trans. There are about 4 seal installers which are a absolute must. the trouble is the cost of these installers is so cost prohibitive that you wouldn't even think about buying them. I made them in my machine shop. Most rebuilders leave these seals alone and say that it wasn't leaking when it came in. I hate that kind of attitude. Do it right or don't do it at all. The reason these seals are so important is because there are actually three sumps in this transmission: Front differential; center differential; and transmission fluid. If they intermix it is big trouble and the trans won't last long."

I have experienced the same thing that estreed described when he said "when you try to do a light acceleration the engine rpms will constantly bounce about 300 RPM's." My A8 has been doing it since the day I bought it used with 173,000 miles on it. I wondered if something was wrong or if it was a peculiarity of the Audi trans. Now I know, something is wrong.

Now my question is this: Is my "rumble" due to a worn torque converter? Or is it something else. Any thoughts?

 

Here’s the final result. I had to have my transmission rebuilt.

My trans died April 16, 2013 in my 2000 A8. I was 35 miles into a 200 mile trip. I came to a red light where I was going to turn right. Just before I came to a stop, the light turned green. As soon as I pressed the gas pedal, there was a loud bang and the car was jolted. All of the gear indicator lights in the PRND4321 display lit up.

The car did not start to accelerate until the engine revs were 2k-3k rpm. Then, it started to move forward, but at a very slow pace. Once It reached about 30 mph, it started to accelerate quicker. It never shifted. I got it to 60 mph and the revs held at 2k rpm. I came to find-out that the trans was in “limp home” mode, which gave me reverse and 5th gear. When all of the gear indicator lights are lit, you are in limp-home mode.

I turned around and drove it 35 miles back home…in limp mode all the way. Every STOP sign was an adventure. The people behind me were not pleased that I accelerated so slowly.

I’ve read a post on the A8 forum titled “Another transmission issue” from Cks69 in May 2011. Cks69 had the exact same symptoms I just described.

I paid $2,661.25 for my rebuild, which included $773.79 labor to remove and re-install the transmission, and $1,690.33 in parts and labor to rebuild it.

The “drum” (whatever that is) was broke, i.e. structurally damaged. So the drum was replaced along with the torque converter, all bearings, all seals, and all gaskets. All of the clutch packs were also rebuilt.

My local mechanic, Rod's Shop, in Gilberts, IL has an association with a transmission shop in Crystal Lake, IL. That transmission shop did the work. It’s guaranteed for 3 years or 30,000 miles. I drive about 17,000 miles per year. So, it’s essentially a 2-year warranty.

I’ve had it out twice so far…driving a total of about 15 miles in urban traffic. The shift from 1st to 2nd and from 2nd to 1st is sometimes hard. All other shifts are smooth. Should I be concerned?

The funky behavior is gone. That is, the engine no longer bounces about 300 rpm right after a shift. Instead, the revs just build uniformly as I accelerate. No up & down business.

Just in case anyone else wants to know, ZF Industries Inc is the manufacturer of the transmission. ZF Industries supplies transmissions to Audi (and other brands). ZF Industries has a re-manufacturing center in Vernon Hills, IL. You cannot buy direct from ZF Industries. Nor can you buy direct from one of ZF’s distributors. The distributors sell only to certified mechanics.

Rod’s Shop quoted me $3,900 for the ZF remanufactured transmission, plus another $1,500 to remove the old transmission and install the remanufactured unit. So, I was looking at a total of $5,400, which was about twice as expensive as the rebuild.

It would have been nice to have a ZF remanufactured unit. ZF explained to me exactly what they do. All wearing parts, bearings, seals, and gaskets are replaced, including the torque converter. All of the clutch packs are rebuilt. All parts that might be re-used are inspected and replaced if any sign of wear or damage. All updates are incorporated, including any programming changes. Sounds like a very thorough re-manufacturing process. Unfortunately, I couldn’t afford to pay the additional $2,700 for it.

According to the ZF website, this is the information on the transmission in my 2000 Audi A8, which was manufactured in December 1999. The website provided a pdf file to download. The pdf file is titled: “ZF Application List for Audi & VW (North American Applications)”
Make Audi
Model A8 Quattro
Engine 4.2L
Year 2000
OE Part # 01L 300 042A
Code EDG
ZF Part # 1058 020 014
Type 5HP24A