4kq differential locks ?s

[Robert M]

>From: Ryan Moon <moon at velaru.net>

>Okay, so for the light to actually come on when you turn the dial switch, 
>the diff has to lock?

    That's how it's designed to work, yes.  And also how it works(ed) on my 
cars.

>
>I did a rear differential drain and fill, Sunday, and found the lines to my 
>rear actuator rotted off, so I replaced them, and found the actuator to 
>work. The light still doesn't come on, on the dash due which I figure is 
>due to the switch being broken and disconnected (the one to the upper rear 
>of the differential.)

    Could be; hard to predict what'll be wrong with an aged machine like 
these :).  If you know for certain that the wires aren't attached to the 
switch, well, that's a good place to start!  To check for actual rear lock, 
raise the car and turn either one rear wheel or the propshaft.  If it's 
locked, all three spinners will spin (wheels x2, propshaft).

>--
>I seem to think the front differential is locked, but the light only comes 
>on when I turn the dial switch in the cab. I'll have to lift the front up 
>and check... just turning one wheel by hand would tell me right? If 
>unlocked the opposite wheel should turn the opposite way? Thus, if locked 
>the wheels would both turn the same way ?

   No, for that test to work you'd need to lock the FRONT diff; the switch 
locks the CENTER.  The front is always open.  IIRC, to check for center lock 
you can raise the rear only and try to turn the propshaft.  If the center is 
locked, you won't be able to spin the propshaft since nothing on the front 
half of the center can turn.

  If the car shudders noticably when going around a tight bend in the dry 
you've got a locked diff somewhere.

>
>Ryan
>On Apr 26, 2005, at 10:45 AM, Robert M wrote:
>
>>The actuators are all plastic, except for the rod.  They're a two-chamber 
>>design, and depending on the position of the switch vac is applied to one 
>>side or the other.  If you're getting odd lock function, you could have a 
>>hose problem (not uncommon IME, these hoses are going on 18+ years old :) 
>>) or an actuator problem (again not uncommon, see above).  The mech can 
>>also get sticky, and is likely to be so if one of the other elements fails 
>>and the mech goes thereby unactuated.
>>
>>On my first 4kq (an 86 with 195k) the rear mech was just frozen up.  
>>Shooting it with PB Blaster and working it by hand 200 times was all it 
>>took to get it to work, and trimming the actuator hoses back about an inch 
>>to eliminate the split zone helped also.
>>
>>On both my 4kq's (my current is an 87 that I bought a couple years ago 
>>with 65k on it :) ) there was physical damage to the front actuator.  In 
>>both cases I was able to remove it (I think it's on the pass side 
>>though*...), clean it, and JB weld the cracked area.
>>
>>IME the lights work well.  I've not had one burn out (aren't they LEDs?) 
>>and on my cars they were a very reliable indicator of actual lock status.  
>>I checked them by hand with all 4 wheels off the ground.  Have a helper 
>>sit in the car and sing "ON!" when the light lights.  Turn a wheel, and 
>>then actuate the lock by hand.  On my cars the actual lock even coincided 
>>perfectly with the light coming on.
>>
>>*getting the front actuator out is a pain- as I recall it's mounted to the 
>>back side of a protective shield that will be caked with ~0.33"/18+ years 
>>of accumulated road grime.  10mm bolts I think, three of them.  No other 
>>parts have to come off, but you'll have to pull some wild contortions to 
>>get it all out.  MAKE SURE YOU KNOW WHICH LINE GOES WHERE BEFORE PULLING 
>>THEM OFF :).  Write yourself a note...
>>
>>Difflocks rule!
>>
>>hth,
>>Robert
>>
>>>From: Shawn Manny <shawn.manny at gmail.com>
>>>Reply-To: Shawn Manny <shawn.manny at gmail.com>
>>>To: Ryan Moon <moon at velaru.net>
>>>CC: quattro at audifans.com
>>>Subject: Re: 4kq differential locks ?s
>>>Date: Tue, 26 Apr 2005 10:39:47 -0500
>>>
>>>They nipples on the actuators are only plastic, they may break off and
>>>if they break when the diff is locked it'll stay that way. IIRC the
>>>center lock is on the drivers side (us spec cars) ontop of the tranny
>>>under the tunnel. The rear lock id on the drivers side as well on the
>>>pumpkin. You may also have a short or bad connection making the light
>>>stay on. Grab your bently and start tracing vac lines, look for broken
>>>plastic chassis lines and shot old rubber under body lines.
>>>
>>>On 4/26/05, Ryan Moon <moon at velaru.net> wrote:
>>> > I'm curious about the diff locks. They are activated by vacuum, but is
>>> > it possible for them to stick or stay locked ?
>>> > Is the front lock mechanism is on top on the transaxle towards the
>>> > passenger side, where you'd have to remove some of the exhaust to get
>>> > to it ?
>>> > The lights on the switch panel in the passenger compartment are
>>> > activated by switches similar to reverse light switches ? So meaning
>>> > the light would only come on if the diff is locked? Or the light would
>>> > stay on if the diff doesn't unlock?
>>> >
>>> > Thanks
>>> > Ryan Moon
>>> >
>>> > _______________________________________________
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>>> > quattro at audifans.com
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>>> >
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>>
>>
>
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