1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Rear end thud

Discussion in 'A4/S4 forum(B5 Chassis)' started by AB5QTS, Jul 28, 2012.

  1. AB5QTS
    Offline

    AB5QTS Member

    Joined:
    Mar 1, 2009
    Messages:
    216
    Likes Received:
    2
    Hey guys,

    I have a thud coming from the rear end on the last thirdish of the clutch pull out in first. It doesn't always happen but I think is becoming more frequent. Only seems to happen in first.

    Any ideas. Oh I have 4wd :racer:

    Cheers
    #1
  2. Bradderz_1988
    Offline

    Bradderz_1988 Dont replace it, Upgrade it !!

    Joined:
    Aug 19, 2010
    Messages:
    3,189
    Likes Received:
    102
    Rear diff carrier bushes or centre diff mount worn out or what mine was the bolts come loose on the diff carrier.
    #2
  3. Chriscooke
    Offline

    Chriscooke Clueless!

    Joined:
    Mar 2, 2012
    Messages:
    411
    Likes Received:
    18
    My dif clonks every so often, doesnt seem to affect the car much yet though.
    #3
  4. AB5QTS
    Offline

    AB5QTS Member

    Joined:
    Mar 1, 2009
    Messages:
    216
    Likes Received:
    2
    Lol. I think I would rather get it sorted first rather than keep it happening then she goes :bye:
    #4
  5. HEKTOR
    Offline

    HEKTOR Member

    Joined:
    Oct 23, 2008
    Messages:
    433
    Likes Received:
    11
    I agree with brad on this. Check all bolts are tight before you go replacing anything.
    #5
  6. Chriscooke
    Offline

    Chriscooke Clueless!

    Joined:
    Mar 2, 2012
    Messages:
    411
    Likes Received:
    18
    Mine was checked by the previous owner at a vag specialist so I'm not overly worried.
    #6
  7. aragorn
    Offline

    aragorn "Stick a V8 in it!" Staff Member Moderator

    Joined:
    Jan 30, 2008
    Messages:
    15,529
    Likes Received:
    301
    I've been chasing this for a long time.

    I've found numerous issues, and changed various parts, but its still there.

    If your lucky its just the rear diff mountings. With mine, i upgraded the rear diff mountings and made everything nice and solidly mounted, and the problem got worse, with a really horrible metallic clank in 1st 2nd and 3rd gear when engaging the clutch.

    I swapped the rear diff out for a spare, still the problem remained.

    I've since swapped the gearbox, replaced a couple of CV's which had play in them, and swapped the upgraded rear diff mounts out for softer ones, which has made it less harsh and bareable, but STILL present.

    Its most noticable now when lifting off the throttle or reapplying it once moving. These are typical symptoms of worn engine and box mounts, and usually you get the gearstick jumping around along with the thunk, but i've replaced/stiffened the engine and box mounts already, and the stick doesnt move at all, so the issue is elsewhere.

    I suspect its a combination of issues all working together. Lots of little bits of slack, combining together and adding up. I know one of the front inner CV's still has a small amount of play, and i've not checked the rear CV's yet, but i suspect at least one of those has play in it too. It seemed to improve significantly when i fixed the play in the propshaft CV and swapped out the gearbox.
    #7
  8. jcb
    Offline

    jcb Active Member

    Joined:
    Sep 19, 2005
    Messages:
    4,118
    Likes Received:
    13
    if you stiffen one part the load is transfered to the next weakest part for any movement.

    get someone under a ramp while you load the clutch with the handbrake on.

    you will be surprised what and by how much things move!
    I had a dyno done years ago and the bloody engine nearly jumped out of the engine bay it was so slack!
    #8
  9. aragorn
    Offline

    aragorn "Stick a V8 in it!" Staff Member Moderator

    Joined:
    Jan 30, 2008
    Messages:
    15,529
    Likes Received:
    301
    yeh exactly. Worn engine, gearbox and diff mounts are a good place to start, they're likely to be knackered anyway

    If its still there after you fix those up, then its gonna be play in the driveline somewhere. Both my front CV's had play in them (i had a spare good CV so swapped it out) as did the propshaft. The diff itself has a fair amount of backlash, but my saloon has similar play in the rear diff and doesnt exhibit the same symptoms.

    My next step is to fix the front CV which i know has play, and pull the rear shafts out and inspect them.
    #9

Share This Page