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Discussion Starter · #1 ·
Recently I bought an '03 XC70 with 160k mi that had been neglected when it comes to regular maintenance and I've been trying to get it sorted out.
I've noticed that I get a little wheel spin if taking off aggressively. I put the car up on jack stands and the rear tires do turn when in drive and I give it a little gas. They don't spin nearly as fast as the front wheels do. The rears also seem a little sluggish to start turning when I give it gas. Is that normal?
This past weekend I changed the angle gear and haldex fluid since I assume they have never been changed. That didn't make a difference.
I've had the DEM tested by BBA and it passed. Could the AOC pump be on it's way out, or is that usually a part that either works or it doesn't?
Other than that I'm not sure what else could be wrong.
 

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Jim Lill Test:

1- jack up one (only) front wheel
2 - put car in neutral
3 - by hand, turn the wheel in the air
4 - observe drive shaft, it should turn
If 4 fails, the angle gear or transmission is faulty.

If it's stripped there's no grip. All other diagnostics require a VIDA/DiCE.

The pump engages the clutch pack in the haldex to allow torque transfer from the driveshaft to the rear diff. If the engine is on, transmission is in drive, all fours wheels off the ground safely, and the AWD is working properl then all four wheels will rotate. In the same senario if you disconnect the pump, the rear will stop spinning, supply 12v to the pump and the rear will spin.

If the rear wheels don't spin while in D, but spin when 12v is applied directly to the pump then it's the DEM. You can also test the pinout on the DEM to see if it's suppling 12v(? Possibly a PWM signal so voltage may read lower) to the pump when it should be engaged. On Xemodex's site they have a diagnostic flow chart for more information.

Also check all the wiring and connections for damage or corrosion.
 

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Discussion Starter · #3 ·
That doesn't really answer my question because technically my car passes those tests.
Should pressing the gas pedal be required to get the rear wheels to spin when all four are off the ground?
How quickly should the rear wheels engage?
Should they be spinning at the same speed as the fronts?

I've read most of the posts on the various tests and the Xemodex flow chart.
Originally I tested with the car off the ground and in drive. The rear wheels don't spin.
Then I jumpered from the 12V that powers the DEM to the AOC pump and that got the rear wheels to spin.
So I sent the DEM to BBA reman and they tested in and said that nothing was wrong with it.
I put the DEM back in, and tested it again. Got the same results except this time I gave it a little gas and found that the rear wheels start to spin slowly.
 

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Forgot to add. It could be the pump, it could be the pressure/temp sensor. Will need a VIDA/DiCE scan to read the DEM for stored codes.

Are you getting a slight chirp, or like a full spin when getting on the throttle.
 

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Discussion Starter · #5 ·
Usually a couple small chirps. Yesterday I got the traction control to come on when pulling away (not hard) from a light on wet pavement.
My S60R never loses traction wet or dry so I know something has to be wrong with the XC.

I have VIDA. I will scan it again. I don't remember any DEM codes before.
 

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Different haldex in both vehicles. 03-05 is gen 2, 06-07 is Gen 3. Gen 2 Haldex will engage with 15* wheel spin (IIRC) where the Gen 3 is a preloaded system coined "Insta Traction", so a chirp from the fronts is fine. I notice it on mine.
 

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Gen II is 90* of spin, and Gen III is 15* IIRC. Non preloaded AOC vs preloaded. (AOC pump primes on start rather than when slippage detected or something) Post P2 V70/S60 AWD is Gen IV and that gets rid of the mechanical pump.

My Gen II R and my Mom's Gen III XC70 are almost identical in the wet... The R just accelerates faster :rolleyes: DSTC might have something to do with it because both cars have DTSC and therefore the computer should intervene (pull power) and the slip shouldn't be noticeable to the driver? Could also be tires. 235 wide vs 215 wide.

Check the pump pressure with VIDA?
 

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with 160k its only a matter of time before the collar sleeve gives out, you might want to check that before digging into the electronics
 
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