Solution for 2005 Volvo XC70 no AWD concerns wheels slipping

Volvo diagnostic tool I use:
Volvo VIDA 2014D from eobdtool.co.uk for €108.49 plus shipping to Netherlands
Car model and year:
2005 Volvo XC70
Car issue:
Got strange wheels slipping today when pulled hard from the stop. No blinking traction icon. A loud clank coming from rear end when I slowly turn with steering wheel at utmost position, sounds like ABS or, perhaps, it is ABS. Roads in MA are currently covered by usual crap left after snow has finally melted.
This is what I saw in a test drive with DiCE/VIDA attached to the car:
In neutral:
 
In drive, pulling from the stop, not very hard:
In R, backing up the hill:

I see nothing criminal. Oil pressure sensor shows linear reaction to AWD demand, does not look like stuck sensor, which jumps from idle pressure to purge valve release pressure.

Also there’s inactive DEM-0006, which has happened at 204900 km, car has now 2062000 km (128113 mi). According to my notes, at the time of this error registered the car had other electrical gremlins, including no starts.

Pulled the DEM plugs, blown with compressed air. Plugs were clean, no signs of oxidation.

Other info on the car: when I bought it in November 2012, it had 80k miles on the clock, dealer serviced. I did stage 0 and, among other things, replaced AOC filter and oil. Both were clean, apparently recently changed. Angle gear had signs of removal, I bet collar sleeve was replaced. AWD was working in this winter, car plowed really well. 2 or 3 weeks ago I called it a season and swapped winter tires Generals Alitmax Arctic (licensed Gislaved Nordfrost) with all-season BFGoodrich Advantage T/A, which still had 3 mm (1/8″) of thread left before tires call for a replacement. Of course I felt immediately how crappy is the traction on these tires after Generals/Gislaved (Swedes know how to make winter tires). On a rainy day car was banging at the rear in the every turn in a flooded multilevel garage, but that is exactly what I also have heard from the Audi with Torsen AWD in front of me (ABS was engaging).

So what do you guys think I’m looking at? Unsatisfactory worn out tires, which easily loose traction and make ABS upset, or is it the first sign of Haldex heading to Valhalla? I could not replicate torque steer and front wheels spinning on a hard pull, which are easily achievable on wife’s FWD V70 with same model BFGoodrich tires.

I solve some problem as following shows:

it was Haldex pump. Replaced, and the rear axle does not feel like living its own life now.

Oil screen on my pump was not that bad… Oil had some clutch material dispersed in it, but still was green, uniform and of about right viscosity.

The job is tough, but not that bad. Probably it is 10x times easier on Gen 4 Haldex, where driveshaft flange does not cover the pump, so no need to drop exhaust and driveshaft for the replacement.

I bought 3 pullers in order to remove the flange on AOC side. The one which worked was actually Craftsman steering wheel puller found at Sears. Two jaw-type pullers didn’t work at all.

The dealer managed to damage the main seal when oil was changed (before I bought the car – I know that work was done, and done by the dealer), so it was very slowly dripping through the flange. Lowest bolt was noticeably wet after sitting through the night.

 

It seems the main reason of failed AOC function was low oil level – didn’t check it in two years since the last oil+filter replacement, and not before starting the job, but when I finally got the pump out I’ve collected way less oil than 0.5 liter I put back at the end. Anyway, after spending slightly over than a day under the car to get to that seal and the pump and the filter, I didn’t want to do it one more time when 10-yo pump will finish its brushes or if it is in fact broken.

Though that could be an advise for other XC70 owners: check oil level if AWD started to misbehave, plus you see traces of oil on the flange or anywhere on Haldex unit. At least, if it turns out that the seal replacement didn’t fix the leak, I’ll be just topping up AOC with oil once a year or so

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