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

Rs4 rear diff different than the 2.5 tdi quattro/s4 diff ?

Discussion in 'A4/S4 forum(B5 Chassis)' started by adamss24, Oct 7, 2009.

  1. adamss24

    adamss24 Well-Known Member

    Joined:
    Jul 3, 2007
    Messages:
    3,815
    Likes Received:
    244
    Hi guys, is there any difference between the 2 differentials or they are exactly the same ? The reason i ask is i am building the said 2.5 tdi quattro as a track car so if the b5 rs4 is a stronger/better unit then i would look for one to swap... Any more details from the peoples in the know ?
     
  2. Google AdSense Guest Advertisement



    to hide this advert.
  3. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    Hmm looking at the part numbers gives us this:

    RS4:
    01H500040L rear axle differential 37:9 / DQA

    A4:

    01H500040G rear axle differential 41:9 / DQA,DRL CKK
    01H500040L rear axle differential 37:9 / DQA

    So the RS4 diff is available on the A4, but oddly enough, DQA is listed with two different final drive ratios...

    Anyone shed any light on that?
     
  4. adamss24

    adamss24 Well-Known Member

    Joined:
    Jul 3, 2007
    Messages:
    3,815
    Likes Received:
    244
    The diff thats on the car now is a DQT, gearbox is DAK... Thats on a '98 b5 2.5 tdi quattro. I believe that being a 6 speed box, the final ratio would be similar to the s4/rs4 wich is also a 6 speed ?!
     
  5. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    Hmm

    DQT isnt listed but DAK is...

    01H500040K rear axle differential 37:9 / DAK

    Seems that DAK is the same ratio as the RS4 diff though at 37:9 (or 4.11:1)

    I wouldnt think there is any advantage changing it. If your going to start messing with diffs then install something like a quaife ATB.
     
  6. adamss24

    adamss24 Well-Known Member

    Joined:
    Jul 3, 2007
    Messages:
    3,815
    Likes Received:
    244
    Sorry, meant DAK... DQT is the gearbox code(only fitted on quattros). I was thinking at a Stasis centre diff wich would give a 4 in 1 diff ! I cannot find any details of Quaife rear diffs, how much it will cost to get one and what benefits they will give ? Reason i asked if the rs4 diff is compatible is 'cause i wanna build the v6 tdi as a track car (half way there !), i know they dont have s4 power but if you fit a BMW x5 turbo(Garrett GTV2260), Iveco nozzles and a decent remap/tuning chip, you will easily see 250Bhp with 500+ Nm of torque while still returning 30Mpg average ! Thats enough to embarass many petrol cars and i love the torque ! Trow a Cummins VP44 injector pump(wich can fuel up to 1000Bhp!) and a big front mounted intercooler and you looking into serious power. The bottom end is strong enough to cope with 500Bhp(it does have strong end bearings and a girder) so it does not need strengtening as yet, then throw a sintered/paddle racing clutch from Sachs and an uprated pressure plate and you'll be able to put all that power on the floor... would be a pig to drive in traffic though...been there done that !
     
  7. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    Quaife ATB's are around £900. I have one for the 1.8tqs. they are different from teh S4/RS4 ones (reason I got mine is the guy bought the wrong one)

    advatages are simple. no pwer loss through either one of the rear wheels..
    Off camber corner or bumps where one wheel lifts more and loses a bit of traction ATB will maintain split of power instead of power drain to one with least grip.
     
  8. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    ^^ To be picky, a Torsen (like an ATB) needs a bit of traction on both wheels to function properly. If you lift a wheel completely, it will act just like a normal open diff.

    The EDL should take take of things should that happen anyway though, so its not THAT relevant in this particular case!
     
  9. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    as described
     
  10. Rallyman

    Rallyman LPG Abuser & have VAGCOM

    Joined:
    Aug 14, 2005
    Messages:
    189
    Likes Received:
    4
  11. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    Go jack a wheel up and see what happens...
     
  12. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    seems to indicate it will lock and maintain power to the gripping wheel.....

    "it automatically biases the torque away from the spinning wheel across the axle, to a constantly varying degree."


    you saying this doesn't work or are you refering to the ""cross axled" effect when you lose grip on two opposite corner on a landrover
     
  13. Rallyman

    Rallyman LPG Abuser & have VAGCOM

    Joined:
    Aug 14, 2005
    Messages:
    189
    Likes Received:
    4
    Dont forget the torsen center diff....... (torsen = similar to atb) not open... or locked
     
  14. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    a Torsen (like an ATB) requires SOME traction for the biasing effect to work. A spinning wheel thats on contact with the tarmac will provide this.

    a quote from wikipedia:

    If you completely lift a wheel (or are stuck in some really slippy mud) the diff will act like an open diff.

    Cross-axling on landrover happens becuase even with the centre diff locked the front and rear diffs are open. So if one wheel on each corner loses grip you stop.

    Quaife ATB's in Landrovers arent very good, because they dont work when one wheel is off the ground, and you still end up cross axled. A proper locker or plate/clutch LSD doesnt do that. The only exception to this is landrovers that are fitted with traction control. Once the ECU realises the wheel is spinngin and applies the brake, the torsen kicks in properly, just as described above.

    Similar thing would happen on a quattro right enough, because it has "electronic diff lock" which is designed to act across each axle to stop one wheel spinning up, and would be much more effective with a ATB than without!
     
  15. Rallyman

    Rallyman LPG Abuser & have VAGCOM

    Joined:
    Aug 14, 2005
    Messages:
    189
    Likes Received:
    4
    electronic = brake is applied by the cars electronics
     
  16. Soupie69uk

    Soupie69uk Owner

    Joined:
    Mar 10, 2004
    Messages:
    2,853
    Likes Received:
    11
    Ed when you going to get this diff in your car?

    You going to do the centre mod to?
     
  17. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    well I am trying to get a rear subframe so I can fit the poly mounts off the car as it will be a bitch of a job with lots of down time if i pull the frame then have to remove teh old ones (quite like to blast and clean a spare one as well.

    diff seals have gone as well so I will just do them all at once.

    what is teh centre mod? washers? probably not TBH

    kind of got my hands full as it is. one week old baby, in laws in residence, engine build will be finshed in a week or so requiringa swap, got a landscaping job in progress that needs to be finished this week and I am meant to be working as well,,,,,,, do want this turbo in before 2011 though!! been in a box far too long!!
     
  18. Soupie69uk

    Soupie69uk Owner

    Joined:
    Mar 10, 2004
    Messages:
    2,853
    Likes Received:
    11
    Yeah I fancy doing the washer mod, just not 100% sure what size of washers I require.

    Looked into it a couple of years ago but then forgot about it.
     
  19. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    sounds like a bodge and one that is stressing something more than it should be which would worry me.
    it shifts a %age rearwards does it?
     
  20. Soupie69uk

    Soupie69uk Owner

    Joined:
    Mar 10, 2004
    Messages:
    2,853
    Likes Received:
    11
    Yeah perhaps.

    It allows an 80:20 split instead of 66.6:33.3 apparently.

    A few people have been running it on their cars for over 2 years with no reported issues.
     
  21. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    rallyman: i know the EDL uses the cars brake, its just a primitive traction control system, however with an ATB it will do a better job.

    Soupie: You do realise it wont change the power distribution? It will still be 50-50 front-rear. All the 66/33 split refers to is the maximum amount of torque the diff can shift one way under loss of grip, and i really cant see that tiny change being worth it, unless your running really big power, and having trouble putting it down when launching hard.
     
  22. Google AdSense Guest Advertisement



    to hide this advert.
  23. Soupie69uk

    Soupie69uk Owner

    Joined:
    Mar 10, 2004
    Messages:
    2,853
    Likes Received:
    11
    Yeah I understand it would be more beneficial to big power cars I just fancied doing it to see what it was like really.

    I am not sure of the power the chaps have that made the change but they found it worthwhile.
     
  24. docurley

    docurley Moderator
    Staff Member Moderator

    Joined:
    Dec 12, 2003
    Messages:
    3,963
    Likes Received:
    40
    guys dont forget I have a rear subframe and diff up for grabs if you need one.
     
  25. jcb

    jcb Active Member
    VCDS Map User

    Joined:
    Sep 19, 2005
    Messages:
    4,125
    Likes Received:
    13
    man, I didn't know that.
    been trying to get hold of AdamS4 for his.

    how much for the frame? sounds like another road trip!
     
  26. Broken Byzan

    Broken Byzan Photographic Moderator
    Staff Member Moderator VCDS Map User Audi A4 quattro

    Joined:
    Apr 26, 2004
    Messages:
    13,021
    Likes Received:
    395
    What ratio is the Diff Dave, sonicdeathmonkey want an rs4/s4 diff. Or is it the one from the TQS
     
  27. docurley

    docurley Moderator
    Staff Member Moderator

    Joined:
    Dec 12, 2003
    Messages:
    3,963
    Likes Received:
    40
    1.8TQ is different to the S4 or RS4
     
  28. SonicDeathmonkey

    Joined:
    Apr 21, 2004
    Messages:
    532
    Likes Received:
    0
    I just checked the speel wheel tag (Cardiff Audi lost my service book, with sticker) and my transmission code is DQA, but someone someone mentioned that there are two final drive ratios specified against DQA?

    Or am I just confusing myself? Hope to have a rear diff lined up off RS246.
     
  29. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

    Joined:
    Jan 30, 2008
    Messages:
    16,694
    Likes Received:
    476
    I think its more a glitch in the vagcat listing.

    All DQAs really should be the same.
     
  30. adamss24

    adamss24 Well-Known Member

    Joined:
    Jul 3, 2007
    Messages:
    3,815
    Likes Received:
    244
    Hi mate, DQA is the rear diff code. I do have the same diff for sale !:icon_thumright:
     
  31. SonicDeathmonkey

    Joined:
    Apr 21, 2004
    Messages:
    532
    Likes Received:
    0
    A DQA diff for sale? PM me with the details:where is it, how much, how many miles it done etc!

    Cheers,
    Steve
     

Share This Page