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Haldex always locked

Discussion in 'A3/S3 Forum (8L Chassis)' started by vovix, Jan 5, 2013.

  1. vovix
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    vovix New Member

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    [Jan 5, 2013]
    Hi,
    I have an 2000 Audi A3 1.8TQ, when I bought the car, the rear diff was broken. Nobody cand say what was the cause. Here is some pics.

    http://s51.radikal.ru/i134/1211/df/ef393fc9798f.jpg
    http://s019.radikal.ru/i605/1211/6b/0efaf6666237.jpg
    http://s019.radikal.ru/i631/1211/e9/60cf4e5e1e65.jpg

    Recently I have changed the diff, b
    ut now it seems like the Haldex is always locked, I can hear when I do slow cornering. You feel and hear the tires rubbing the road. When driving in a strait line, there's no strange noise. The Haldex, ABS or engine has no DTC's.When I disconnect the haldex connector, the problem is gone.
    Tryed to replace the electrical control module from my old haldex, but problem remains.
    Anyone an idea what can be the problem? Maybe that was the problem crashing the last diff.

    Here you can see the new diff (left) and old one (right).
    http://imageshack.us/a/img836/3066/imag1265o.jpg
    #1
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  3. vovix
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    vovix New Member

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    [Jan 5, 2013]
    any idea? help me please
    #2
  4. sportstractor
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    sportstractor Chugger

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    [Jan 5, 2013]
    Have you checked the haldex pump?
    #3
  5. vovix
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    vovix New Member

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    [Jan 5, 2013]
    No, but it must work if haldex is locked, right?
    Some time ago i got front right ABS sensor error, DTC cleared without changing the sensor. until now has no error. but ABS, traction control everything works. Can be the problem with haldex from ABS sensor?
    #4
  6. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 5, 2013]
    Bill has an S3 in with the the same issue... with the haldex electrically connected it locks but pull the fuse and its fine which suggests the plates are ok but there is an issue with the controller... the pre-charge pump isn't running all the time (which is another known fault) so we currently think the controller (which has a variable valve in it to control locking of the haldex) is faulty...


    This particular car however has been driving with no fluid in the haldex for some time... it came in for a haldex oil change and the seal was missing from the filler plug plus there was no actual oil in the haldex at all... refilled the haldex and oil poured out of the controller gasket... new gasket fitted and pre-charged tested ok... test drove the car and the diff was locking...

    Pulled the fuse and all is good but obviously no AWD...

    <tuffty/>
    #5
  7. vovix
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    vovix New Member

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    [Jan 5, 2013]
    <tuffty/>, thank you for reply, but problem solved?
    #6
  8. Gops
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    Gops 6th gear @7000rpm

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    [Jan 5, 2013]
    Change the oil. If you replaced it, then chances are the oil is old.
    #7
  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 5, 2013]
    Not yet.... waiting to hear from the customer as to how he wishes to proceed... will update the forum though once I find out what happens

    <tuffty/>
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  10. vovix
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    vovix New Member

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    [Jan 5, 2013]

    Ok, thank you
    Last edited: Jan 5, 2013
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  11. vovix
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    vovix New Member

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    [Jan 5, 2013]
    In diff I have replaced but in the haldex not yet, cannot find at the moment. The oil is old and not enough, this can be the problem?
    #10
  12. downhilldave77
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    downhilldave77 Member

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    [Jan 5, 2013]
    hi all its my s3 that tuffty mentioned i will look for a used haldex controller.i wonder how long the haldex had no oil i guess thats why you should check the haldex servicing before you buy a s3
    #11
  13. Erf
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    Erf Member

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    [Jan 5, 2013]
    Will be interesting to see what happens as this issue has cropped up a number of times. I've replaced virtually every part and now suspect it might be the abs pump / ecu...
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  14. vovix
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    vovix New Member

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    [Jan 5, 2013]
    I don't think that problem is in oil pump, old oil or control module, because VCDS can turn on/off coupling, result that all components works. Logically haldex control module not recieve correct information from ABS.
    Tomorrow I will try to check/change ABS sensor.
    #13
  15. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 5, 2013]
    If the ABS sensors were at fault then this would come up in the ABS fault codes... any ABS related issues would take priority fault wise over the haldex... if there was an ABS fault then the haldex would be disabled not broken... as for the haldex recieving incorrect info there are huge amounts of fail safes in place on safety related equipment like ABS... there will be checksums and other tests that the controllers will be checking to make sure nothing is corrupt... the controller is more than electronics... it contains a valve that alters the pressure to the clutch plates... pre-charge pump primes the system and the main pressure (so I understand it) is derived from the rotation of the propshaft as the precharge pump is not man enough for the pressure required to maintain the lock...

    I am fairly convinced the issue is haldex controller related but I am keeping an open mind as issues with the haldex is a new experience for me personally... this is the first car I have seen personally with this issue so looking forward to getting to the bottom of it...

    <tuffty/>
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  16. Pabl0
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    Pabl0 Member

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    [Jan 5, 2013]
    I'm currently waiting for a haldex controller to sort the same issue..

    Looking as the cars history the ABS unit has been replaced at a decent cost (£0000's) for one reason or another so maybe that was Audi's answer for the issue... hoping a controller will cure all.
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  17. vovix
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    vovix New Member

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    [Jan 5, 2013]
    post here the results please.
    #16
  18. thegoal007
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    thegoal007 Another S3 owner....

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    [Jan 6, 2013]
    If by removing the haldex fuse cures the issue - doesn't that then indicate an electrical issue - maybe with the controller and perhaps anything else the fuse disables indirectly such as the abs/ecu (but then you can probably pull that fuse out first and try !).
    #17
  19. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 6, 2013]
    The fuse is for the haldex only... its the same fuse we pull for doing dyno runs... the ABS is still functional... like I said... keeping an open mind on this but I am fairly convinced the issue revolves around the controller in context of the car thats at Bill's currently... I don't think it is the electronics but it could be the regulating valve and its motor...

    Here is a thread that has a link to a really useful haldex self study guide...
    Audi Addict &bull; Haldex Self Study Guide for VW & Audis

    <tuffty/>
    #18
  20. Erf
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    Erf Member

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    [Jan 6, 2013]
    Hi Tuffty,

    My haldex is permanently in 4wd. I've replaced the rear diff, the pre charge pump and done a oil and filter change. The only error I get is on the front wheel speed sensor (intermittent fault). I've replaced the sensor but still have the same intermittent fault. Could the ABS ecu be causing a false error on the wheel speed sensor?

    Cheers.
    Erf
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  21. Pabl0
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    Pabl0 Member

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    [Jan 6, 2013]
    Have you replaced the haldex controller?
    #20
  22. chris99
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    chris99 s3 driver

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    [Jan 6, 2013]
    Hi, is this the one also posted on the Badger 5 FB page?
    I heard before about diff locking after running with no oil/old oil, and everytime the fuse was taken out it ran just FWD, so the regulating valve inside the control unit makes sense to me..
    #21
  23. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 6, 2013]
    Yes it is mate... :)

    <tuffty/>
    #22
  24. downhilldave77
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    downhilldave77 Member

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    [Jan 6, 2013]
    hey tuffty do you know if a haldex controller from a audi tt would be the same i am hoping to get one tomorrow and take it over to bills hopefully then my haldex will be working then cheers
    #23
  25. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 6, 2013]
    Year of the vehicle is more important... as far as I am aware they are not tied to a particular model (people have used R32 haldex/diffs to replace faulty S3 ones in the past) but early controllers used o-rings as seals whereas later ones (like yours) use a metal crush gasket...

    Dunno what years yours is but if the TT one is from a similar or later year then should be ok..

    <tuffty/>
    #24
  26. downhilldave77
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    downhilldave77 Member

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    [Jan 6, 2013]
    cheers mines a 2002 so i will look for one around the same year hopefully that will sort the problem
    #25
  27. vovix
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    vovix New Member

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    [Jan 9, 2013]
    replaced wheel speed sensor, haldex also remain blocked. any ideas? old sensor was good, I don't know why error apears. Repeat, when I have changed control unit, leaked some oil from haldex, can haldex couple if oil level is under the normal?
    #26
  28. thegoal007
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    thegoal007 Another S3 owner....

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    [Jan 9, 2013]
    yes the fuse is for the haldex only, but in order for it do it's job properly it relies on a number of sensors (all very well documented) including the abs/ecu unit. So by removing the fuse for the haldex you in fact knocking out all of the additional elements that feed into the haldex and thus assume it must be the haldex controller. After all it could be one of the longtitude/latitude sensors feeding incorrect information when turning on full lock and thus telling the haldex to apply rear left or right wheel brake. Yeh disabling the fuse and problem has gone, but that because one of those sensors is not managing to send it's information to the haldex and not the fault of the haldex unit itself (after all it's simply doing what it's told).

    On the other hand I'm just not sure you can actually isolate individual elements before removing the the haldex fuse as you wouldn't know how the haldex will react to lack of certain information it receives - it may just render it inoperative i.e the same as pulling the fuse out in the first place !

    And hey, don't forget it may still be the haldex controller all along :)
    NOTE: strangely enough I'm sure when I took my fuse31 out the abs also ceased to work. Must check that out again. I presume that applies to all S3 99-03.
    Last edited: Jan 9, 2013
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  29. Pabl0
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    Pabl0 Member

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    [Jan 9, 2013]
    I've sourced a bargain priced controller and its on its way to me now, hopefully will be here for the weekend and time/weather permitting I'll fit it and see if it sorts out my problem; rear locking up when turning tightly.

    Hopefully it will be a fix, otherwise i guess its best to bite the bullet and change haldex/diff with a known good version.
    #28
  30. Erf
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    Erf Member

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    [Jan 9, 2013]
    When you take fuse 31, does the ABS warning light come on? Mine doesn't so I'm assuming the ABS is still working with fuse 31 out!
    #29
  31. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 9, 2013]
    Long/lang sensors, steering position and abs sensors operate without caring if the haldex is there or not... ESP is available on FWD cars too...

    The Haldex has nothing to do with left/right brakes at all... its a clutch pack... all it does is connect drive from the prop shaft to the rear diff... thats it... its the ABS controller and the that manages ESP...

    ABS, ESP and Haldex AWD is a modular system but there is of course dependencies along the line... ABS is essentially top of the tree... when you have an ABS fault you lose ESP and essentially AWD too... this would show up as an ABS fault... ESP is a function of ABS so ESP control is lost when certain sensors are faulty but you don't always lose ABS... the steering and G sensors are ESP related rather than ABS... if you lose a wheel sensor then the whole system becomes inoperative... no ABS, ESP or Haldex (I believe)...

    ESP is even switched off when certain engine sensors go down too such as the MAF sensor... ESP uses engine management to control torque request as well as the ABS system to control wheel spin...

    Its all very complex but... any fault in the system will be flagged... as it is then it relatively easy to isolate the system thats at fault... the software has comprehensive diagnostics.. the number of maps you have to adjust when doing big turbo conversion for example just so that the extra load, boost, airflow etc doesn't trigger limp modes and other ECU protection systems is staggering... this redundancy and protection is built into all Bosch systems and its supporting hardware...

    In VCDS when logging in the various modules you will see (if you have the labels set up correctly) the upper and lower bounds of any logged parameter... when a signal goes 'out of bounds' then a fault code is flagged... the software in all these modules also use a checksum system to ensure that no data gets corrupt... the ECU in particular checks its checksums on a regular basis to make sure that nothing has happened to the code that could (for example) cause it to misinterpret the torque requested from the throttle pedal potentially causing it to go wide open throttle as you are driving down a busy high street (the throttle pedal is completely disconnected electronically and virtually from the throttle body itself... the software determines how much to open the throttle based on the requested load from the driver... but thats another discussion entirely)

    Anyhoo... the point is... I am not assuming anything... the diagnosis is based on information gleaned from monitoring the various modules and checking fault codes on the whole system... as non of the sensors are malfunctioning then logic suggests its a mechanical issue... seeing as the haldex operates hydraulically and the 'electronics' essentially operates a valve to determine how much pressure to use to clamp the clutch shut then seeing as (and yes this was tested too) the haldex does actually engage and it does have AWD when the fronts start to lose traction the only real issue is that the clutch does not fully disengage when its supposed to even when the 'electronics' have 'done' so... this suggests that the motor or the valve is sticking before it gets fully set in its 'disengaged' state...

    The reason why its disengaging fully when there is no power is that there is no pressure being generated by the pump... when there is power applied then with the valve not closing properly there is enough pressure to engage the clutch slightly...

    Of course there is no real way of telling until the controller is off and apart... (or replaced) but seeing as the haldex has spent a fair amount of time 'running' with no oil and what did come out of it was thick and glupey then I think its a fair assessment to say the controller is not a happy bunny..

    No assumptions here...

    <tuffty/>
    #30
  32. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 10, 2013]
    erm... Haldex does'nt do this job, ESP does via abs controller on cars equipped with esp... Early S3 did'nt have esp but still had haldex
    #31
  33. vovix
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    vovix New Member

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    [Jan 11, 2013]
    today I have tried to pull out fuse 31, but haldex remain blocked, ABS and traction control works.
    #32
  34. Pabl0
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    Pabl0 Member

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    [Jan 12, 2013]
    Right an update.

    My second hand controller came, £40 delivered = bargain.

    Fitted this morning on the drive with the car on little ramps in this lovely tropical weather were having and after reading afew guides I thought it was going to be tricky, actually it was very easy. Afew tips, use elastic bands to hold the gasket whilst you get it back in position and get the screws started, cut them oncethere both biting. Tie some string/rope around the rear connector before pulling it through so you can easily pull the new wire back .

    It fixed my issue, rear wheel/s locking when Turning tightly at low speed and the car feels like it's dragging.

    Oil looked clean (that came out) but ill still renew so it's topped up, I can concentrate on fun mods now!
    #33
  35. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 12, 2013]
    well done dude
    good news
    #34
  36. vovix
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    vovix New Member

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    [Jan 12, 2013]
    Today I have fixed problem too. In my case was a mechanical problem, not electrical. Haldex totally disassembled, every channel and valve blew under air jet, everything cleaned. Old oil was very dirty, in the one of the channel I have found a small rock about 4mm, have no idea how it got there. Assembled, filled new oil, new filter. Start engine, not immediately began to check haldex, but drive slow for about 10 minutes to fill haldex channels and pump with oil, and after that test on the snow. Works perfect, haldex block only when front wheels slips. Thank you all.
    Last edited: Jan 13, 2013
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  37. thegoal007
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    thegoal007 Another S3 owner....

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    [Jan 13, 2013]
    badger5, braking is possibly the wrong word to have mentioned - should have said rear wheels locking ! So would I guess correctly in saying the ESP is causing this lockup which is the abs unit working in communication with the Haldex or is this action purely with the abs unit ??

    demons uk, what a3 model/year do you have ? Also when you had the issue of locking when driving round very tight roundabouts did you notice the esp light flicker or turning right/left at speed ?
    Last edited: Jan 13, 2013
    #36
  38. Pabl0
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    Pabl0 Member

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    [Jan 13, 2013]
    2001 S3 AMK

    Yep, lights used to flicker often but not always when the rear wheel/s were dragging..

    Guarantee it will be your controller bud, check the connection first though as this might be corroded..
    #37
  39. thegoal007
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    thegoal007 Another S3 owner....

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    [Jan 13, 2013]
    It may be, but you were extremely lucky to get one for £40 and a good working one at that price !
    I would not be too quick to guarantee it's the controller - vovix above and many others turned out to have a different diagnosis. And some just change the haldex oil/filter and fix their problem ! What I do know is in most cases there is NEVER a fault showing !
    #38
  40. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 13, 2013]
    mechanical lockup... hopping wheels.. no Centre Diff... when haldex is locked up.
    if esp flickers its because the rear wheels relative to the fronts are unable to traverse their own arc when turning, not because of esp... No functioning centre diff being the cause.. (no centre diff present! - lol)
    #39
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  41. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 24, 2013]
    #40

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