play in driveline
05-11-2005, 04:28 AM
#1
AudiWorld Super User
Thread Starter
play in driveline
I've been plagued by a somewhat sloppy feeling drivetrain since I bought the car. I hear a clunk when I put it into Drive and if I go back and forth between P and R you can hear it prety clearly. It's the same sound my old (American) cars made when a u-joint went bad. Anyway, I got in my pit and started to investigate. If I grab the driveshaft at the transmission end and rotate it back and forth, I can hear the "clunk". I know that some play is normal, I just don't know how much. I can take a measurement but it rotates maybe 3/4". On top of that, if I push up and down in the same place, there's some up/down play as well. I think my problem is in the differential and/or output flange. If I didn't do it myself, I would think maybe the output flange wasn't tight enough. I had the problem before I removed it to replace the seal though. Any ideas ? I'm afraid it might be in the differential but hoping you guys have some other thoughts...
Bob
Bob
05-11-2005, 05:41 AM
#3
AudiWorld Super User
Thread Starter
that's interesting because I haven't found anyone else with the same issue
and I've driven a bunch even with higher mileage. I don't have any issues with the transmission itself, it shifts flawlessly. As a matter of fact, it was replaced at 40k by the dealer before I bought the car so it only has 40k on it. If you want to shoot me an email maybe we can talk and compare notes.
Bob
rdunne14@comcast.net
Bob
rdunne14@comcast.net
05-11-2005, 06:08 AM
#4
AudiWorld Super User
Notes? You want notes? Here's mine from Subtitled's car
He still has the problem, Audi has replaced the tranny, the driveshaft, but not the rear end nor the half shafts.
I'm going to do a bunch of work on his car including replacing both front half shafts. His car is a 99.....
I have this in word format if you want me to email it to you so you don't get all the stupid little errors signs.....
---------------------------start--------------
Subtitled Transmissions Problems (or should it be titled  eother than transmission problems�) (initial post)
Subtitled (Martin is his name) came by my place yesterday to have a look at his tranny problems. We spent a few hours looking at it, putting some euro corner and side marer lights on Richard‼sup>TM</sup>s (another lister) A8 and having lunch. Audi‼sup>TM</sup>s seem to be a nice way to meet nice people.
I would not say that Martin‼sup>TM</sup>s problem is a tranny problem, but a problem with the drivetrain and after pulling codes, the throttle position indictor.
Symptoms of the problem:
When the car is put into gear with the foot on the brake, there is a  eclunk†that can be heard and felt. If it is put in drive, then back to reverse, then to drive again, it clunks every time. This is one problem.
The second problem is when driving the car around very slowly, and just putting the gas on lightly and lifting again, the car lurches as if somebody is pressing the gas hard. Also, when it is shifted into TIP mode, and you are slowing down, once it shifts into first gear it really lurches forward and has a  eclunk†in the drive train.
The first thing we did was to hook my computer up to the car and pull the codes, the tranny had two fault codes:
Transmission Codes:
2 DTC's Found:
18169 - Shift Lock (N110): Short to Ground
35-10 - - - Intermittent
18264 - Throttle Potentiometer (G69): Error Message from ECU
35-10 - - - Intermittent
The shift lock is working correctly, and the two positions of the shift lock are either on or off, depending if your foot is on the brake or not. I did not clear the code because I want the dealer to see it. If they replaced the tranny and some wires touched where they shouldn‼sup>TM</sup>t of during installation, maybe this code could have been produced. Regardless, I don‼sup>TM</sup>t think it has anything to do with his problems.
The second was the throttle potentiometer (or throttle position indicator as it is written in the Bently). At first I thought that it was odd that the tranny would see this.
After searching the Bently and looking at things, the following items are transferred from the ECU (engine control unit) to the TCU (transmission control unit):
1. Engine speed
2. Engine coolant temperature
3. Throttle position
4. Vehicle speed sensor signal from instrument cluster
5. Engine torque (actual torque)
There were a couple reasons why the TCU could get the throttle position indicator code including a bad TCU, but one was that the actual TPI (throttle position indicator) was bad. This information is transferred from the ECU to the TCU through the CAN-bus wire data exchange. So that‼sup>TM</sup>s how they talk to each other. So I got the great idea to search for codes on the engine.
Engine codes were as follows:
1 DTC's Found:
16505 - Throttle Position Sensor (G69): Implausible Signal
35-10 - - - Intermittent
It sure made sense now that the TPI was bad, and it is intermittent. Martin complains that the longer the engine is on (warmer it gets) the worse off it is, even when the ambient temperature is higher, it is worse.
If the TPI is bad, I would not be surprised if it is thermally affected. As it gets warmer, it has more and more error.
I did not have time to do the resistance checks of the TPI, the engine plastic has to come off, and TPI is right near the firewall. Should be very easy to check with a multimeter.
So this could be the source of his problem with the car lurching at very low gas pedal efforts, the ECU is getting bad info on the throttle position. Regardless, it is my opinion that it is the first thing that needs to fixed before additional troubleshooting should or can be performed.
I then got under his car while he went and put it in drive and then reverse and back to drive. It sure sounds like there is a bad CV joint, driveshaft universal (or CV joint whatever it has) or loose mount (like the torque support mount on the front of the engine or maybe a driveshaft bearing support).
When looking at the exhaust system going from drive to reverse and back again, it moved vertically about ½†to as much as 1â€. I do not know what would be normal, but it sure looked like too much movement to me.
So the thumping noise that Martin is hearing is the loose component (CV joint, torque mount, etc.) swapping from the  edrive side†to the  ecoast side†when a reversal in torque is applied on the bad component. This also needs to be found and fixed. If the ECU is getting improper data from the TPI and putting too much gas into the system, this will be noticeable at low engine loads (slow speeds, just about coasting) causing a relatively large torque input into the drive train. This combined with the loose component, is causing the undesirable  etransmission problems†that Martin is describing. I don‼sup>TM</sup>t think it has anything to do with the transmission, just the drive train.
So my conclusion is as follows:
1. Before doing anything else, the TPI ECU fault must be cleared. This will require either replacement of the TPI or recalibration (there is some adjustment in the Bently but didn‼sup>TM</sup>t read it in detail). This is required to move forward in solving the problem.
2. Clear the brake switch fault code and see if it comes back. If not, maybe it was shorted to ground during the new transmission installation, not a problem.
3. Check the drive shaft, all axle CV joints, engine mounts, transmission mounts, torque support, etc. for looseness. This would be relatively easy to do on a lift with two people. Repair as necessary.
After this is complete, Martin should have a tight A8 again!
Does this sound reasonable? Other input is greatly appreciated.
Reply
Do you like the A8 where you want to keep it?
Answer: Yes, then get it fixed. It's a simple mechanical problem. No need to trade it in for a more expensive one.
Answer: No, then don't worry about it, just get rid of it.
You have slight clunking at very low torque inputs to the car (causing the clunking to be more pronounced). The car drivetrain moves up and down RELATIVE to the body when going from drive to reverse with the brake on.
There are 10 CV joint in the drivetrain and one U joint. I don't think these are your problems. They would not cause a relative movement between the body and drivetrain.
What would cause this is a suspension to body mount. So each wheel assembly is mounted to the body, the rear diff, the driveshaft bearing, the tranny and the engine.
If you look under the car and see which way it is moving (up or down), you will get an idea which corner (s) are compressing/relaxing during torque reversals. Then go to the suspect corner and inspect for problems while doing torque reversals.
Now what I'm thinking it might be: I think it could be a tranny or motor mount, including the torque support on the front of the engine. If the A8 motor mounts are like the type 44 mounts, they are oil filled. What if one went bad? Probably wouldn't be hard to see at all.
My number one hunch (which usually proves to be wrong) is one of the motor mounts.
Pw
12/2/02 Inspection
Martin came over today so I could check for fault codes and take another look at it.
To recall the situation, he bought an Audi assured 99 A8 with 40K miles. Has a serious clunk in the drive train (which I verified he still has). The dealer replaced the transmission with no change in the problem, then I looked at it. It had two fault codes, one for the brake switch and one for the throttle position indicator. Both are gone, there are no fault codes. There was nothing wrong with either item from my understanding.
Then the next step was for the dealer to replace the driveshaft, which had no effect. Audi technical was involved at this point and they made the recommendation to replace the rear differential (final drive • rear) and it has had no effect.
Martin is very frustrated and I don‼sup>TM</sup>t blame him. However, it is not a super obvious problem, at least to me.
So he came over today and we looked at it. First, I will describe the clunk. It does not clunk all the time, it happens in both first and second gear, but as the speed of the car increases (and momentum of the car), it seems to get less and less noticeable.
It is most noticeable when the car is in first gear, with small throttle inputs (and lifting completely off the gas). I still feel it is happening when a torque reversal is happening, i.e. going from  edrive†to  ecoastâ€.
It feels as if it has excessive clearance in a CV joint, or excessive gear lash in one of the drive pinions in the drive train. Ever had a 1977 Ford F150? Shift from reverse to drive and feel the U joints in the drive train torquing from coast to drive due to excessive clearance, that‼sup>TM</sup>s exactly what it feels like.
The weird thing is that it doesn‼sup>TM</sup>t always do it, and once it does it, it is relatively violent. My 1997 A8 does not do anything like this.
Once again, I don‼sup>TM</sup>t have a garage, so we couldn‼sup>TM</sup>t jack it up, not that would help much, the lower engine cover is on. All I could do was get down on my back and inspect and listen the best I could.
The sound is most definitely coming from the front of the car, forward of where the drive shaft couples to the distributor gear. So these components includes the engine, distributor gear (which houses the torsen, does it even have a torsen? This is where the output of the auto transmission is taken off and sent back forward to the final drive - front and out to the driveshaft), final drive • front, and front CV joints and axles.
Once it gets going (i.e. the clunk starts), it‼sup>TM</sup>s making quite the noise when a torque reversal happens. Martin turned the wheels and I inspected the front drive shafts while he went from drive to reverse and back again. It‼sup>TM</sup>s clunking during the torque reversal, but the front drive shafts do not seem to have any forward or reverse rotation, so the CV joints do not seem to be the problem.
With the front drive shafts removed from the possible problems, we are down to the distributor gear, final drive • front and the engine and transmission mounts including the torque support.
The top of the engine seems to be moving about ½†up and down during torque reversals. My car is not here, so I cannot compare. If mine has less movement or the same movement, it would not surprise me. I cannot verify that the torque support is tight, but the only thing that is moving on it is the rubber which is compressing slightly; seems like it is doing its job. And if it was bad, I don‼sup>TM</sup>t think it would cause a clunking noise from below the engine.
So what I am thinking it might be is excessive back last (gear lash) in the distributor gear or the final drive • front. I can‼sup>TM</sup>t figure out why it comes and goes though. These two components are sections of gears that take power out of the auto transmission, step it to the proper speed, and using a bull and pinion gear, send it back forward along side of the transmission to the front wheels. The final drive • front then drives the front wheels with another gear.
If there is excessive clearance in one of these components, it would cause the large  eclunk†in the drive train that is happening during torque reversals.
What I do not know, is if these components are replaced when the automatic transmission is replaced. If so, I guess you could throw my theory out the window. But if that is the case, if the car is put up on a lift and the belly pan is removed, it shouldn‼sup>TM</sup>t be that hard to figure out where the noise is coming from.
If they are not replaced during transmission replacement, I would be looking at them next.
Help? Thoughts? Thanks!
Once last bit of information:
The torque converter in all cases was  eOPEN†when the clunking was occurring. The TC slip speed was going from 0 RPM to about 125 or as much as 200 RPM during the clunking. The data sampling rate of the ross-tech software is not high, so it‼sup>TM</sup>s hard to do transient monitoring. It works best when the car is at steady state.
I'm going to do a bunch of work on his car including replacing both front half shafts. His car is a 99.....
I have this in word format if you want me to email it to you so you don't get all the stupid little errors signs.....
---------------------------start--------------
Subtitled Transmissions Problems (or should it be titled  eother than transmission problems�) (initial post)
Subtitled (Martin is his name) came by my place yesterday to have a look at his tranny problems. We spent a few hours looking at it, putting some euro corner and side marer lights on Richard‼sup>TM</sup>s (another lister) A8 and having lunch. Audi‼sup>TM</sup>s seem to be a nice way to meet nice people.
I would not say that Martin‼sup>TM</sup>s problem is a tranny problem, but a problem with the drivetrain and after pulling codes, the throttle position indictor.
Symptoms of the problem:
When the car is put into gear with the foot on the brake, there is a  eclunk†that can be heard and felt. If it is put in drive, then back to reverse, then to drive again, it clunks every time. This is one problem.
The second problem is when driving the car around very slowly, and just putting the gas on lightly and lifting again, the car lurches as if somebody is pressing the gas hard. Also, when it is shifted into TIP mode, and you are slowing down, once it shifts into first gear it really lurches forward and has a  eclunk†in the drive train.
The first thing we did was to hook my computer up to the car and pull the codes, the tranny had two fault codes:
Transmission Codes:
2 DTC's Found:
18169 - Shift Lock (N110): Short to Ground
35-10 - - - Intermittent
18264 - Throttle Potentiometer (G69): Error Message from ECU
35-10 - - - Intermittent
The shift lock is working correctly, and the two positions of the shift lock are either on or off, depending if your foot is on the brake or not. I did not clear the code because I want the dealer to see it. If they replaced the tranny and some wires touched where they shouldn‼sup>TM</sup>t of during installation, maybe this code could have been produced. Regardless, I don‼sup>TM</sup>t think it has anything to do with his problems.
The second was the throttle potentiometer (or throttle position indicator as it is written in the Bently). At first I thought that it was odd that the tranny would see this.
After searching the Bently and looking at things, the following items are transferred from the ECU (engine control unit) to the TCU (transmission control unit):
1. Engine speed
2. Engine coolant temperature
3. Throttle position
4. Vehicle speed sensor signal from instrument cluster
5. Engine torque (actual torque)
There were a couple reasons why the TCU could get the throttle position indicator code including a bad TCU, but one was that the actual TPI (throttle position indicator) was bad. This information is transferred from the ECU to the TCU through the CAN-bus wire data exchange. So that‼sup>TM</sup>s how they talk to each other. So I got the great idea to search for codes on the engine.
Engine codes were as follows:
1 DTC's Found:
16505 - Throttle Position Sensor (G69): Implausible Signal
35-10 - - - Intermittent
It sure made sense now that the TPI was bad, and it is intermittent. Martin complains that the longer the engine is on (warmer it gets) the worse off it is, even when the ambient temperature is higher, it is worse.
If the TPI is bad, I would not be surprised if it is thermally affected. As it gets warmer, it has more and more error.
I did not have time to do the resistance checks of the TPI, the engine plastic has to come off, and TPI is right near the firewall. Should be very easy to check with a multimeter.
So this could be the source of his problem with the car lurching at very low gas pedal efforts, the ECU is getting bad info on the throttle position. Regardless, it is my opinion that it is the first thing that needs to fixed before additional troubleshooting should or can be performed.
I then got under his car while he went and put it in drive and then reverse and back to drive. It sure sounds like there is a bad CV joint, driveshaft universal (or CV joint whatever it has) or loose mount (like the torque support mount on the front of the engine or maybe a driveshaft bearing support).
When looking at the exhaust system going from drive to reverse and back again, it moved vertically about ½†to as much as 1â€. I do not know what would be normal, but it sure looked like too much movement to me.
So the thumping noise that Martin is hearing is the loose component (CV joint, torque mount, etc.) swapping from the  edrive side†to the  ecoast side†when a reversal in torque is applied on the bad component. This also needs to be found and fixed. If the ECU is getting improper data from the TPI and putting too much gas into the system, this will be noticeable at low engine loads (slow speeds, just about coasting) causing a relatively large torque input into the drive train. This combined with the loose component, is causing the undesirable  etransmission problems†that Martin is describing. I don‼sup>TM</sup>t think it has anything to do with the transmission, just the drive train.
So my conclusion is as follows:
1. Before doing anything else, the TPI ECU fault must be cleared. This will require either replacement of the TPI or recalibration (there is some adjustment in the Bently but didn‼sup>TM</sup>t read it in detail). This is required to move forward in solving the problem.
2. Clear the brake switch fault code and see if it comes back. If not, maybe it was shorted to ground during the new transmission installation, not a problem.
3. Check the drive shaft, all axle CV joints, engine mounts, transmission mounts, torque support, etc. for looseness. This would be relatively easy to do on a lift with two people. Repair as necessary.
After this is complete, Martin should have a tight A8 again!
Does this sound reasonable? Other input is greatly appreciated.
Reply
Do you like the A8 where you want to keep it?
Answer: Yes, then get it fixed. It's a simple mechanical problem. No need to trade it in for a more expensive one.
Answer: No, then don't worry about it, just get rid of it.
You have slight clunking at very low torque inputs to the car (causing the clunking to be more pronounced). The car drivetrain moves up and down RELATIVE to the body when going from drive to reverse with the brake on.
There are 10 CV joint in the drivetrain and one U joint. I don't think these are your problems. They would not cause a relative movement between the body and drivetrain.
What would cause this is a suspension to body mount. So each wheel assembly is mounted to the body, the rear diff, the driveshaft bearing, the tranny and the engine.
If you look under the car and see which way it is moving (up or down), you will get an idea which corner (s) are compressing/relaxing during torque reversals. Then go to the suspect corner and inspect for problems while doing torque reversals.
Now what I'm thinking it might be: I think it could be a tranny or motor mount, including the torque support on the front of the engine. If the A8 motor mounts are like the type 44 mounts, they are oil filled. What if one went bad? Probably wouldn't be hard to see at all.
My number one hunch (which usually proves to be wrong) is one of the motor mounts.
Pw
12/2/02 Inspection
Martin came over today so I could check for fault codes and take another look at it.
To recall the situation, he bought an Audi assured 99 A8 with 40K miles. Has a serious clunk in the drive train (which I verified he still has). The dealer replaced the transmission with no change in the problem, then I looked at it. It had two fault codes, one for the brake switch and one for the throttle position indicator. Both are gone, there are no fault codes. There was nothing wrong with either item from my understanding.
Then the next step was for the dealer to replace the driveshaft, which had no effect. Audi technical was involved at this point and they made the recommendation to replace the rear differential (final drive • rear) and it has had no effect.
Martin is very frustrated and I don‼sup>TM</sup>t blame him. However, it is not a super obvious problem, at least to me.
So he came over today and we looked at it. First, I will describe the clunk. It does not clunk all the time, it happens in both first and second gear, but as the speed of the car increases (and momentum of the car), it seems to get less and less noticeable.
It is most noticeable when the car is in first gear, with small throttle inputs (and lifting completely off the gas). I still feel it is happening when a torque reversal is happening, i.e. going from  edrive†to  ecoastâ€.
It feels as if it has excessive clearance in a CV joint, or excessive gear lash in one of the drive pinions in the drive train. Ever had a 1977 Ford F150? Shift from reverse to drive and feel the U joints in the drive train torquing from coast to drive due to excessive clearance, that‼sup>TM</sup>s exactly what it feels like.
The weird thing is that it doesn‼sup>TM</sup>t always do it, and once it does it, it is relatively violent. My 1997 A8 does not do anything like this.
Once again, I don‼sup>TM</sup>t have a garage, so we couldn‼sup>TM</sup>t jack it up, not that would help much, the lower engine cover is on. All I could do was get down on my back and inspect and listen the best I could.
The sound is most definitely coming from the front of the car, forward of where the drive shaft couples to the distributor gear. So these components includes the engine, distributor gear (which houses the torsen, does it even have a torsen? This is where the output of the auto transmission is taken off and sent back forward to the final drive - front and out to the driveshaft), final drive • front, and front CV joints and axles.
Once it gets going (i.e. the clunk starts), it‼sup>TM</sup>s making quite the noise when a torque reversal happens. Martin turned the wheels and I inspected the front drive shafts while he went from drive to reverse and back again. It‼sup>TM</sup>s clunking during the torque reversal, but the front drive shafts do not seem to have any forward or reverse rotation, so the CV joints do not seem to be the problem.
With the front drive shafts removed from the possible problems, we are down to the distributor gear, final drive • front and the engine and transmission mounts including the torque support.
The top of the engine seems to be moving about ½†up and down during torque reversals. My car is not here, so I cannot compare. If mine has less movement or the same movement, it would not surprise me. I cannot verify that the torque support is tight, but the only thing that is moving on it is the rubber which is compressing slightly; seems like it is doing its job. And if it was bad, I don‼sup>TM</sup>t think it would cause a clunking noise from below the engine.
So what I am thinking it might be is excessive back last (gear lash) in the distributor gear or the final drive • front. I can‼sup>TM</sup>t figure out why it comes and goes though. These two components are sections of gears that take power out of the auto transmission, step it to the proper speed, and using a bull and pinion gear, send it back forward along side of the transmission to the front wheels. The final drive • front then drives the front wheels with another gear.
If there is excessive clearance in one of these components, it would cause the large  eclunk†in the drive train that is happening during torque reversals.
What I do not know, is if these components are replaced when the automatic transmission is replaced. If so, I guess you could throw my theory out the window. But if that is the case, if the car is put up on a lift and the belly pan is removed, it shouldn‼sup>TM</sup>t be that hard to figure out where the noise is coming from.
If they are not replaced during transmission replacement, I would be looking at them next.
Help? Thoughts? Thanks!
Once last bit of information:
The torque converter in all cases was  eOPEN†when the clunking was occurring. The TC slip speed was going from 0 RPM to about 125 or as much as 200 RPM during the clunking. The data sampling rate of the ross-tech software is not high, so it‼sup>TM</sup>s hard to do transient monitoring. It works best when the car is at steady state.
05-11-2005, 06:48 AM
#5
AudiWorld Super User
Thread Starter
Good stuff... describes my issue to a tee but I don't have any fault codes.
Transmission was replaced but I don't know if that included the final drive or not. Front motor mount/dampener was replaced by me a while back. I believe that the motor and trans mounts are original. As you describe it, it feels like gear lash in the forward diff. Small throttle inputs - yep, that's it. I guess I could replace the trans mounts first. I don't think that they are too expensive. I see some movement but don't know if it's excessive or not. Were you able to hear the clunking by moving the driveshaft by hand ? As I mentioned, I have play/noise when rotating it AND some up/down play as well. Good stuff, thanks for posting it.
Bob
Bob
05-11-2005, 08:18 AM
#7
Might want to read this thread completely as well:
<a href="https://forums.audiworld.com/a8/msgs/83310.phtml">https://forums.audiworld.com/a8/msgs/83310.phtml</a>
I noticed a lot of slop in my driveline as well when my previous problem started.
I noticed a lot of slop in my driveline as well when my previous problem started.
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