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Preventative maintenance for Haldex AWD

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dk2020
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dk2020

Preventative maintenance for Haldex AWD

Post by dk2020 » Mon Apr 13, 2020 5:35 pm

Hi all,

New to the forum with a new-to-me 2004 V70R. Spoke to two Volvo shops today and discussed getting car to Stage 0. I'm particularly concerned about the AWD system given what I've read on the forum :shock:. The prior owner had replaced the Haldex filter/fluid recently. One shop didn't recommend anything more for the AWD system and said to address it when it breaks down (inevitable?). The other shop recommended replacing the Haldex pump (~$700). Anyone with any thoughts/experience with this? I live in Northeast so do need the AWD atleast in the winter.

BTW, first shop said, the most common large problem he would expect was a breakdown of the DEM as opposed to anything wrong with the angle gear.

Thanks.

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Re: Preventative maintenance for Haldex AWD

Post by - Pete - » Mon Apr 13, 2020 10:25 pm

Congratulations on the acquisition!
M66 or Aisin trans?
How many miles?

Yes the Haldex AWD concerns a lot of people & it does have its points of failure.

A rudimentary “check” you can perform without any scan tools is (w/ignition on, engine running) press and hold the “read” button on the end of the turn signal stalk. Then, while still holding the “read” button, press 2X the rear fog light button on the light switch module (LSM). In the lower left dash screen you’ll now see “Checking DTC’s...”, followed by “DTC’s in vehicle...”. Next press the “read” button to scroll through all the available modules in the car (1 at a time). If they say “ready” that means it’s functioning. If the module says “checking...” it’s still reading the module. If it says “... DTC set..” that means there is a fault code that has been “set” in that module. Don’t freak out if a bunch of them say “DTC set”.

You’re going to scroll the modules until you get to “DEM”, which stands for “Differential Electronic Module”. Hopefully your DIM screen will show “ready”.

I personally would never take the advice to “just wait until it fails...” with these. Especially when it comes to the oil/filter & lube in the AOC/DEM and front/rear diffs. Proactivity goes a long way with these cars.

From nearest the transmission to farthest from it, your AWD can fail at 1) the “Collar sleeve” (small, internally splined “collar” that transmits power from the transmission to your transfer case/bevel gear), 2) the gears/bearings within the bevel/angle gear itself can fail, and of course 3) the AOC/DEM and it’s pump can fail. Very few rear diff failures, but a possibility to add to the mix.

First off, have you been under the car?
How long ago did the P/O say the AOC/DEM oil/filter was done?
Does the car seem to have been well taken care of or beat on?
Does the AWD seem to be working? A simple way to check RWD function is to jack up either the L/R side of the car & chock the wheels left on the ground. Put the car in gear and verify that both front & rear wheel spin on the side off the ground. This is not failsafe, but should tell you if the collar sleeve is still intact &/or Haldex is working.

An easy way to tell if the filter has been changed to the updated version is to look at the AOC/DEM for this; it will have a “finned” cover concealing it. As you can see, the pump is adjacent. To replace the pump and/or filter removing the driveshaft from the rear flange is necessary.

7F3C4EF6-F7D1-4B66-8F1D-DE9D58785F6F.png

DEM pumps cost $275-300 for a high quality, Volvo-equivalent pump (part only, not labor or AOC oil). There are rebuild kits available, but this hasn’t been a well documented undertaking. As others will point out, the pump itself is not the only failure point in the DEM, but probably the most frequently encountered & notorious. The sensation that is felt when the DEM pump is failing is a lot like what it would feel like to be accelerating over a garden hose or the like. Sort of a “skipping” driveline shock type of sensation.

Lastly, saying that the DEM will fail before the angle gear isn’t and hasn’t always been proven to be true. Having done both, I’d have to say that I would hope for a DEM (pump) failure over a bevel gear failure. Unless, of course, it was a collar sleeve. Those are cheap & not tough to replace. $140-150. Buuuuut, when the splines on a collar sleeve are no longer there...the same can be true of the splines on the bevel gear input side. It’s a tough equation of which to pick sides.

Sorry for the longwindedness.
2001 V70XC 146k
2004 V70 AWD 141k
2004 V70R M66 144k
2004 XC70 287k
2006 XC70 155k Sold

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