Page 1 of 2 12 LastLast
Results 1 to 18 of 19

Thread: Which one at fault - TC or Gearbox?

  1. #1
    Registered User
    Join Date
    Jan 2015
    Posts
    16

    Which one at fault - TC or Gearbox?

    Sorry for this being my first post but hopefully someone on here can shed some light on this....
    Here's the scenario-
    Driving along in D doing about 40-50mph, pull out to pass slower traffic in front and apply some gentle throttle.
    Where i would expect the gearbox to go down one gear and pull cleanly, the car hunts for the right gear as if it can't make up its mind.
    We make forward motion but not cleanly, the engine hunting, the car lurching forward but not violently.
    If i let my foot off the throtle and reapply it seems to clear itself, either selecting a lower gear or if it doesn't need it pulling cleanly away.
    None of these things happen if i use the paddles to select a lower gear or am in tiptro.
    Also when flooring the throttle from standstill or very low speeds the revs rise with very little forward motion and then the gearbox catches up and off we go.
    No trans fault codes shows up on a VAGCOM scan.
    I gave the gearbox a service a couple of weeks ago but it has made no difference.
    I have done some live logs and converted them to graphs which i have attached for anyone interested to have a look at.

    In the file Gearbox graphs:
    Blue - Engine speed
    Red - Transmission input speed
    Yellow - Speed (km/h)
    Green - TC slip speed
    The ATF temp was between 48 and 55 degrees C when i did this.
    The top graph was 3rd,4th and 5th gear if i remember correctly, the bottom graph is all in 4th gear.

    In the file Gearbox graph 2:
    Blue - Engine speed
    Red - Transmission input speed
    Yellow - Transmission output speed
    Green - Speed (km/h)
    Maroon - TC slip speed
    ATF temp was between 64 and 78 degrees C.
    This time it was heavy throttle from standstill, not quite wide open throttle, but close.
    When throttle was applied the revs rose quickly but it wasn't accompanied by massive forward motion, seemed to take a moment or two for the gearbox to catch up - felt like a slipping clutch if it had been a manual.
    Engine speed and trans input speed traces seem very closely linked which would seem to suggest TC is OK but is the TC slip speed trace too high?
    Anybody have any thoughts?
    Would love to be able to diagnose the source of the problem.
    Attached Thumbnails Attached Thumbnails Gearbox graph 2.pdf   Gearbox graphs.pdf  

  2. #2
    Registered User
    Join Date
    Jul 2008
    Location
    Out there
    Posts
    7,780
    What are we working on?

  3. #3
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    Sorry, C5 RS6

  4. #4
    Registered User lswing's Avatar
    Join Date
    May 2011
    Location
    Eugene, OR, again...
    Posts
    4,760
    Sounds very much like a slipping trans clutch, which I never got codes for, both times mine failed. Soon I would think the slips will become more pronounced, adding some bangs/hard shifts as the clutches finally catch. The failed TC symptoms are a slightly delayed or mushy feel, but the shifting still seems relatively decent, and you tend to get a code for the TC.

    Either way, at this point, if one needs to be service do both. Costs are roughty $500 for new TC, $3-6k Trans, ~$2-4k labor...

    One way to confirm it's the TC is this. 5th gear cruising in Tip at 50mph. Give it some gas, not enough to hit the blasted kickdown/trans destroyer switch. You should see your RPMs rise ~500 or more before the car picks up speed as the TC slips as it should be fully locked at this point.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  5. #5
    Registered User
    Join Date
    Jul 2008
    Location
    Out there
    Posts
    7,780
    Miles

    History of repairs

    Mods

    How long have you owned and driven

    Is this a new condition

    Last 6 vin

  6. #6
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    DHall1, the car has 125,000 miles on, had a new gearbox at 95,000 which was serviced at 108,000 and 2 weeks ago.
    Has a stage 1 Revo remap circa 500bhp.
    I have had the car for 2 years and use it most days. This problem has been lurking around for about a year - i just drive around the problem, but it has always annoyed me that it is not right!
    Vin= 901243

    Iswing, i did the TC test today and car picked up speed with no slip, so seems TC is working correctly.

  7. #7
    Registered User
    Join Date
    Jul 2008
    Location
    Out there
    Posts
    7,780
    Doesit act the same in sport mode.

    Can you switch off the revo and try sport mode?

    May consider a TCU chip

  8. #8
    Registered User lswing's Avatar
    Join Date
    May 2011
    Location
    Eugene, OR, again...
    Posts
    4,760
    Dave, I think he's in Europe, so VIN may not match our specs. That true MGtrophy?

    I too have the Revo map, it produces some good power and torque, although I found mine to run a bit lean so had to update that.

    Odd things can happen with these transmissions. I'm going to guess the TC is locking up as you stated. When I first got my car the TC fail to lock code was showing, and when I tried the test I got around 400-500 bump in RPMs, confirming its failure to lock up, or bad seal basically. That was fixed and is still good.

    I had a rebuilt/new trans put in a few years ago, and it broke/started slipping within 8 months. Luckily it was under warranty, but the labor and other costs still added up. For me, it was jumping out of gear under hard acceleration, specifically in 3rd. Basically WOT in third, and around 4-4,500RPMs it would spin/slip and make an aggressive gear jump to 4th. You ever have this, maybe try a 3rd gear pull in Tip and see? I had driven the car hard at times, ~200 WOT shifts through the gears, and figure I toasted a clutch, but we never confirmed it.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  9. #9
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    Guys, i am in Scotland - Iswing i am having a parallel conversation with you on RS246 (Frustratedracer)!
    Car is 2004 year.
    Yes, get the same problems in Sport mode.
    I generally don't drive the car hard and because i know there is a problem i tend to use the paddles or tiptro if i am giving it some welly.
    Yes, i have had the WOT symptoms you describe which can be a bit embarrassing when you are trying to show someone how fast your car is!
    I will try the 3rd gear pull in tiptro and see what happens.
    All your help is much appreciated.

  10. #10
    Registered User lswing's Avatar
    Join Date
    May 2011
    Location
    Eugene, OR, again...
    Posts
    4,760
    Yep, I thought it was you, cheers, best of luck here.

    I would say "crap!" after hearing you have the same jumping issues under WOT. I too had switched to driving in Tip only as it was just messy to drive in auto. We tried all tests, switched fluid twice, nothing helped nor could we diagnose the issue. I fully believe I cooked some clutches driving hard. The symptoms you describe feel just like a clutch slipping on a manual; you feel the slipping/fail to grab hard, then it finally grabs.

    My bad habit was doing some 0-80's in Tip, WOT, and letting the car shift when it hit redline. It was a fast bam...bam....bam...but looking back the high torque and high rpms must have eaten up or cooked the clutches with heat. One hot summer night I did three 0-60 runs against a new Porsche 4S, I think that cooked it, everything was really hot, and I did multiple WOT shifts on each run.

    I feel the Revo tune is very good at producing torque (sure they all are), and torque is the trans killer. Most tunes would do this also if driven the same I suppose. One of my worries was that I never let the clutches work/bed in good enough when the trans was new. I've had my new trans for a year, but hardly any WOT shifts, I just back off a touch now, as I'm confident this is a weak point even on a rebuilt trans.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  11. #11
    Registered User ttboost's Avatar
    Join Date
    May 2009
    Location
    CT
    Posts
    2,457
    the death knell tolls...
    Likely the TC caused the transmission failure...I think you need both now...Mine failed with no codes...

  12. #12
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    OK, 3rd gear WOT test today while in tiptro.
    Did it 4 times and one occasion when i floored it from approx. 2000rpm the revs rose sharply before the gearbox caught up and engaged roughly.
    The other 3 were drama free but were started from higher revs so the engine probably wasn't under as much load.
    My feeling is that the TC is probably OK and something is wrong with the box. It is a bit annoying i am not getting any fault codes that point to the actual problem but in a strange way it is a bit comforting that others have had failure with out any codes showing.
    I will probably just live with it for the time being until it gets undriveable and start saving for new TC/Gbox, but it does spoil the driving experience a bit.

  13. #13
    Registered User lswing's Avatar
    Join Date
    May 2011
    Location
    Eugene, OR, again...
    Posts
    4,760
    Quote Originally Posted by MGtrophy View Post
    OK, 3rd gear WOT test today while in tiptro.
    Did it 4 times and one occasion when i floored it from approx. 2000rpm the revs rose sharply before the gearbox caught up and engaged roughly.
    The other 3 were drama free but were started from higher revs so the engine probably wasn't under as much load.
    My feeling is that the TC is probably OK and something is wrong with the box. It is a bit annoying i am not getting any fault codes that point to the actual problem but in a strange way it is a bit comforting that others have had failure with out any codes showing.
    I will probably just live with it for the time being until it gets undriveable and start saving for new TC/Gbox, but it does spoil the driving experience a bit.
    All points that I agree with and found with my trans. I think yours is a bit worse as my slipping was only under max torque. I've seen the dyno charts for my car, and peak was ~4,500 in 3rd, RIGHT where it would pop out of gear to 4th.

    One thing I always figured could be a problem causing this is valve body pressure, even though it was maxed out with the upgraded trans. For whatever reason we ruled that out, but it's almost as if there isn't enough pressure to hold the clutch discs together. Oddly enough each time we changed the fluid it was very clean, either the filter got it, or the discs were just glazed from heat/friction....or it was some pressure issue. Again, no code, on both of my failed trans.

    There are so many damned little seals in this trans that I always figured one could be leaking and not holding full clutch pressure. I feel I could have driven mine for years, it just sucked to have it pop out of gear under max load, and was only 7-8 months old with 2,000 miles when it went bad.

    When my first/original trans failed, it would jump out of gear for a while, but it failed drastically one day. Revs spiking really high and banging into gear, almost undriveable unless really light throttle. We found the oil full of shavings when it was looked at after the fail.

    Check out any options with your VB pressure, any testing you can do, or maybe replace, as it's accessible. There is also a quick patch/fuse fix that bumps up your VB pressure significantly. One of the users on here did that to patch up a slipping trans, but it was very rough shifting of course. 907854 or something if he chimes in. Cheers, best of luck man!
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  14. #14
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    Cheers mate,
    Does an MTM TCU do anything to increase VB pressure?
    I might have a look at the VB some time and see if i can do anything with it but i don't know what tests i can do on it though.
    Any work i will do myself so i will save on labor but need to start looking at the cost of a recon tranny and probably an Ace TC.

  15. #15
    Registered User lswing's Avatar
    Join Date
    May 2011
    Location
    Eugene, OR, again...
    Posts
    4,760
    I think the MTM TCU just tightens up the shift (makes it faster) with the electronic signal, in theory reducing time the clutches spend slipping next to each other, but does not change VB pressure. Get one for sure, I've had mine for years, helps some and just makes driving better.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  16. #16
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    OK, will look into it.
    Thanks for all your help - much appreciated.

  17. #17
    Registered User PCMacDr's Avatar
    Join Date
    Dec 2014
    Location
    San Fernando
    Posts
    156
    Quote Originally Posted by MGtrophy View Post
    OK, will look into it.
    Thanks for all your help - much appreciated.
    any update to your situation?
    2003 Audi RS6
    Daytona Grey
    APR EMCS

  18. #18
    Registered User
    Join Date
    Jan 2015
    Posts
    16
    Not really.
    I now have a Viper TCU map which made a small difference to the way the box shifts through the gears.
    The box still has the same symptoms and i am just biding my time until it gets so bad i need to change it - just delaying the inevitable really!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •