aduggs

I've read through a few previous posts on this, and it sounds like there is a number of possible reasons. What causes the clunking during acceleration when there is a torque reversal (engine is causing the car to decelerate)? There must be play in the drivetrain somewhere. The clunk does not always happen, but is much worse around 10-5 MPH.

I'm experiencing the same symptoms as in this previous post: https://www.audiworld.com/forums/sho...play+driveline

I have a feeling that the clunk is coming from the front. Could be half-shafts or CVs? When you jack up one of the front wheels, is there supposed to be play? I can manually rotate the wheel 10-15 degrees when it is in the air. Not sure if this is normal play.

How easy is it to determine if it is transmission mounts?

Thanks for the help!

silverd2

There is always normal play in the front and rear diffs...normal open diffs with helical gears. You can grab the central drive shaft and turn it a little..that's normal radial play in the rear diff.

CV's failing usually make an audible rotating clicking in corners, synchronized with the speed of the car. CV's with lots of play (esp fronts) result in pulsating wobble in the steering wheel...even driving straight. To check for play in CV's, each half-shaft has to be grasped while trying to turn that wheel back and forth...should be zero radial play in any CV joint...just normal in/out play on the inner joints.

Drive-train play from acceleration to deceleration is normal in all these cars, because of the diffs normal play...feeling or hearing an audible clunk is NOT normal...could be any of many suspension parts, motor or trans mounts...even (and esp) the front engine torque mount visible under the hood (between radiator and engine...left side looking in from front). Some one could actual shift from "D" to "R" (foot on brake!) while you watch this mount...should be NO play..only compression/decompression of the rubber in the mount.

aduggs

Sorry, I should have mentioned that I do not experience the clunk when shifting from 'D' to 'R'. There is no clicking during tight turns and no vibration at all in the steering wheel at speed.

The clunk does not happen all the time. It seems to me that in colder conditions, the clunk is lessened or gone all together.

It only clunks when going at slow speeds like in a traffic jam when you are constantly on/off on the gas. There's a slight delay between the RPM of the engine to actual acceleration. Once the play has been taken up, there is a metallic clunk - like gear lash.

It's most prominent when coasting from 10 MPH down to 5 MPH. If I try to accelerate from 5 MHP, the clunk can be heard and the car very subtly lurches forward. Based on this, I do not think that it is suspension related.

I'm starting to think diff or trans mount. Is there a way to confirm this without a lift?

aduggs

If this problem was suspension related, what components should I look at? Would there most likely be a loose control arm? I find this hard to believe since there is no clunking while going over bumps.

I am also experiencing some rear suspension sound while going around slow speed turns. I just dismissed it as being a rear anti-sway bar link problem since it sounded more like a creaking noise.

Thanks again.

A8CT

Is it a facelift car (2000+)?

This is fairly common and most noticeable as you mention in stop/go traffic or coming up to a light. I'm on my 3rd D2 and they all do it to some extent. Almsot feels like the cars stops and then a split second later the drivetrain follows.

There's an adaption sequence you can do through vag-com that will eliminate it on a temporary basis until the TCU re-learns the shift patterns. I do it every couple of months on my cars whenever I have vag-com connected.

If nothing else, this will rule out other system components in less than a minute on the laptop. I'll post it, I don't have it in front of me right now.

That's pretty funny... just clicked on the link in your post after I posted this reponse only to find that was me 6 years ago!


Bob

aduggs

I hope that is all it takes to fix - that's great news! I was worried it was something a bit more $$$.

Please post the adaption when you can. I would like to try it out.

It is a facelift - 2000.

Thanks,
Alex

A8CT

Try this:

Go into Trans module on vag-com
Engine mode - measuring blocks
Group 060
Switch to Basic Settings

You'll hear some clicking and it will say "ADP OK"

done


Bob

aduggs

Bob, thanks posting this. I was not able to access group 060 through the Auto Trans module, so I assume this is for the engine. I will try it out tonight and report back if it solves my clunking problem.

This procedure resets the throttle body:

Turn the key on but do not start the car.

[Select]
[01 - Engine]
[Measuring Blocks - 08]
Group 060
[Go!]
[Switch to basic settings]
Once you do this you will see the top right display say ADP RUN. The TB adaptation is being done as soon as you switch to basic settings. You will see the values change and hear the TB cycle for the first few seconds then it will stop. Leave it in Basic Settings for about 30 seconds.
[Switch to Meas. Blocks] button and you're all set.

This is very interesting since I noticed the clunking behavior start after cleaning the TB. I read on Ross-Tech article that this needs to be reset after doing this. You could check if your TB is dirty as this could be why you need to reset it every couple months.

A8CT

Yes, that's it. I had "Trans Mode" written on a piece of paper in the garage when I copied the instructions.

Let me know if this makes a difference, I never thought about cleaning the TB as the root cause even though I have cleaned them. Now that I think about it, I'm not doing the adapation nearly as often on my wife's car after having the Throttle body removed and cleaned for another job.


Bob

aduggs

So I reset the TB a couple times now. It has helped, but my clunking still persists.

I now notice a loud creaking sound when on/off the gas at low speed. It is loud enough to almost be a popping noise. This is a separate noise from the metallic clunk. Is this a symptom of a bad rear CV?

I plan to jack the car up this weekend and check if there is any play in the CVs. Is there a proper method to this, or should I just start yanking/twisting the half shafts?