Now that i'm getting everything buttoned up on the car after the transmission rebuild I came accross something last night that doesen't seem right.
I put the car back on the stands as I was going to drain the transmission fluid and check the magents for any metal or debris just to be sure all is ok as I ran the car up and down my street a couple of times already, but mostly had it idling in the garage so I figured most of any potential debris would have washed down already. Don't get me wrong, the reduild was done in a very clean workshop, but just in case.

Once on the stands I crawled under it while it was idling and found a noise coming from the front part of the transmission, directly the area where the Torque Converter is located. It happens when the car is idling both in park and in neutral. The best I can describe this noise is like a quiet bad crank bearing in an engine, but much quieter. The transmission oil pan and the front 1/3 of the transmission has a slight vibration to it that are in rhythm with the noise. Now I thought it is the TC but that is a brand new rebuilt unit from a reputable shop in the US.

One thing i do know is that I'm possibly 0.5-1 litres short on transmission fluid as I ran out when I was filling it up, but at temperature and at idle, it took nearly three litres more that when filled up with the engine off, for a total of nearly 9.5 litres.

At first I thought that it has the same characteristics as the torque converter was off center when installed, but that is very hard to do since the converter mounting plate has the raised edges where the TC sits within. One thing I do seem to remember that when I installed the TC, there wasn't any sort of additional bushing on the part of the TC that inserts into the pocket in the crankshaft to take up any slack.

Now this noise does not sound like metal tearing, or grinding gears, but a soft thump that is heard and felt in the body of the transmission.

If anyone has any experiance with this sort of thing please let me know. I will report tomorrow after I pull the oil pan tonight if I find any shavings or debris on the magnets or in the filter.

Rebuild Summary:
Complete rebuild kit, friction plates and steels.
Brand new A-Clutch and input shaft - was broken
Rebuilt TC - From a trans shop in Texas
All new seals and gaskets.
Filter kit and Pentosin fluid.

Did not rebuild the Valve body, bought the full kit but was discouraged by a local transmission shop. Shift quality is excellent.

Thanks,

KP

 

Since the A8 also has the 4.2L engine try an A8 site:
http://www.audipages.com/Tech_Articl...eshooting.html
Also, try doing a search of the forum, as there was one with an A6 4.2L which had rebuilt the transmission himself.

 

Well,
The fluid looked dark, actually dark cloudy, but not burned. Smealled brand new. Maybe this is the actual color of the fluid, as I never before had this much fluid poured into a white plastic container.

I dropped the transmission oil pan last night and this is what I found.
The magnets had very little black residue on them, propably from the clutch packs initially wearing in.
No shavings, or metal pieces anywhere, but what I did find was a little bit of very fine aluminum like dust in the bottom of the pan. Now thinking back I can't think of any two aluminum parts that would rub together to cause this, so perhaps it may be normal break in. I'm not sure.

I cleaned everything with brake cleaner and reasembled. Filled the transmission with the fluid, at proper temperature. It actuall took another .5 lites more, so I was initially short.

The car idled for about 20 minutes, went through all gears, ran the car up to 80km/h or so to get everything lubricated again.

The longer I listen to this noise, the more is sounds like a muffled thumping, like the torque converter was off center and rubbing against the pump housing as it rotated. It doesen't get worse or better, just stays the same.

I'm baffled, i'm gonna have a mechanic buddy of mine listen to it tonight.

THanks for any advice,

JR

 

Well I had the mechanica friend of mine listen to the car last night and his suggestion is that the noise is coming from the Torque converter. He suggests that its either of theh three torque converter bolts not tight enough or the bolts that hold the flexplate on to the crank.

Now that I think back when I did the rear main seal on the engine, there was a 3.5mm spacer between the crankshaft and the flexplate and a 1.5mm washer under the flexplate bolts. I know for a fact I made a point of this when I reassembled everything to make sure the spacer and the washer go in their correct locations, but who knows, it might have been a friday night when I was doing all this.

The one thing I also remember that when I initially installed the transmission and was bolting it up, the torque converter would not slide all the was against the flexplate. I pulled it apart again and noticed that a couple of the flexplate bolts had rubbed off paint on the back of the torque converter when they would touch if they could. I thought that was strange, but looking in the Bentley, it did not show any sort of additional spacers or shims so I didn't think much of it. The torque conveter being a brand new re-build, i took in faith that all is ok and kept on bolting on parts.

Now last night i went through every book, service manual and picture I have on all this work and can't figure out what i could have installed incorrectly in there.

My friend's suggestion was to first to unbolt the torque converter from the flex plate, push the TC as far as possible into the transmission and start the car. If the noise stops, this would point to the TC as it will be standing still while the engine is idling. Then, unfortunately I have to pull the transmission out and really what's the issue in there. The only good part is I can now have that transmission out in about 4 hours.

I'll keep an update,

JR

 

So i pulled the transmission out last night, had it out in about three hours. What I found was absoluetely nothing. The TC bolts are all tight, the flexp-late to crank bolts were all torqued, the crank shim and flexplate spacer were in their correct locations... I'm stumped.

The only thing out of the ordinary was the indent mark of three flrxplate bolts on the back of the TC, i know that shouldnt be.

Found this writeup on line regarding the installation of a TC and transmission. I never really paid attantion to any paint or any rust inside to the crankshaft, but I didn't see anything out of the ordinary. I'll have a better look tomorrow.

http://www.partshp.com/ConverterInstructions.htm


I'll have my mechanic friend look at it all apart tomorrow, then we'll see.


JR

 

Update, noise issue still not solved. Cleaned the TC and flexplate mating surfaces, cleaned the port where the TC dowel slides into the crankshaft, re-installed everything back together, filled the transmission with fluid, and still noisy.

At this point i'm officially stumped. One thing i noticed is that when i was filling the transmission with fluid at temperature, VAG-COM read a temperature of 35 celcius, yet the fluid in the pan was almost cool to the touch...is this normal???

I thought that if the fluid temperature reads 35 celcius, that should be through the entire transmission. Maybe threre is a fluid flow problem with my transmission, and that's why the noise???

Maybe it's the pump making noise... but the car drives fine.

Any suggestions?
Could someone go under their 00 4.2 and tell me if there is any noises coming from the transmission when idling? Can you feel any vibration in the oil pan?

Thanks for any input.

JR

 

Wow - great write up and a heck of a job (glad I have an MT6 and a good indie shop). Maybe the noise was there all the time. Sometimes when you look for strange noises, you find them.

 

Since the flex plate and torque converter rotate together, any interference between the two won't, directly, cause a noise. Indirectly, however, it could if the interference caused something to bend into something else.

Did you carefully examine the inside of the bellhousing to see if there were any marks?

You said the noise only occurs in Park or Neutral, what about Drive? Does the problem go away once you put it in drive? If so, then the problem is inside the transmission.

If it still occurs in Drive, does it occur in all gears? You may have to rig up a microphone, amp and headset to test this while driving, but you need to test this.

If it occurs in all gears, does it vary frequency when you speed up and slow down? Does it vary with engine speed or with road speed? If with engine speed, the problem is in the input sode of the transmission. If with road speed, it is in the output side.

If it varies with engine speed, does it sounds like a once per engine revolution noise or multiple times per revolution (or, rarely, once per multiple revolutions)?

Bob

 

Hey Bob, thanks for your suggestions.

I'm starting to think more and more that it's the converter or the pump itself, this is why.
1. There is absolutely no marks on the inside of the bell housing or on the back side of the engine from the torque converter rubbing anywhere.

2. The noise is constant and in rhythm with the rotation of the engine, which is why i'm thinking it's the TC or pump.

3. The noise is same in Netral and Park. But gets slower as you put the transmission into gear, as the engine RPM drops slightly.


I talked with the shop that I purchased the Rebuilt Torque converter from last night. Their suggestion was to drive the car for 100 or so miles and check if the noise is still there.

I'll try that and report again.

JR

 

If it is in the torque convertor itself, the noise should go away when the torque convertor locks up. If does not go away after your 100 mile break in period, put the car up on jack stands (4) and set the cruise control at 70 and see if you can still hear the noise.

Bob