Replaced a rear diff in a friend's 04 xc70, here's how it went...

[Hamfist]

His rear diff was howling, we found it near empty and leaking from a side seal, got a great used one from a local yard, got the fitler kit and put fresh fluid and filter in, now for removal, we found we don't have to drop the whole rear carrier assembly.

Well after scowering the interwebs and YouTube for some help and instructions, and finding very little, we tore into it.

Up on multiple jackstands... Used 6 to be safe.


Wheels off, caliper off, bracket off, rotor off. Exhaust off from cat back, Easy stuff.

Removed wheel bolts and bearings. Removed parking brake backing plate and cable.

Removed trailing arms, and control arms.

Removed both strut assemblies, one bolt in the cargo area, two body mounts, one arm bolt.

Removed sway bar. Could not get the knuckle separated from the upper aluminum arm.

Removed the 8 bolts for the rear cover housing the diff.

Removed both axles. This part is 2 person. I was banging, pulling prying, everything I could think of, nothing worked. With an assistant pulling, they popped out In 3 seconds flat, we felt dumb.

Then We came to the realization that we did not need to drop the whole thing, as random threads suggested... Took off the driveshaft bolts and the one bolt that held the rear end in... Lowered it with a jack.

Installed the new one. Almost done with reassemblely.

:)

[Hamfist]

His rear diff was howling, we found it near empty and leaking from a side seal, got a great used one from a local yard, got the fitler kit and put fresh fluid and filter in, now for removal, we found we don't have to drop the whole rear carrier assembly.

Well after scowering the interwebs and YouTube for some help and instructions, and finding very little, we tore into it.

Up on multiple jackstands... Used 6 to be safe.


Wheels off, caliper off, bracket off, rotor off. Exhaust off from cat back, Easy stuff.

Removed wheel bolts and bearings. Removed parking brake backing plate and cable.

Removed trailing arms, and control arms.

Removed both strut assemblies, one bolt in the cargo area, two body mounts, one arm bolt.

Removed sway bar. Could not get the knuckle separated from the upper aluminum arm.

Removed the 8 bolts for the rear cover housing the diff.

Removed both axles. This part is 2 person. I was banging, pulling prying, everything I could think of, nothing worked. With an assistant pulling, they popped out In 3 seconds flat, we felt dumb.

Then We came to the realization that we did not need to drop the whole thing, as random threads suggested... Took off the driveshaft bolts and the one bolt that held the rear end in... Lowered it with a jack.

Installed the new one. Almost done with reassemblely.

:)

Annnd, the diff won't work. Many codes in the dash from brake failure, to transmission errors to engine electrical...

Rear tires won't turn at all.

Just like my stereo install, I did not disconnect the battery before unhooking the diff and installing the new one.

I'm guessing I gotta get that vida and proceed with that.

[Xheart]

Is this same as VC http://www.volvoxc.com/0/resources/how-to/pdf/2001-volvo-v70-xc-awd-l5-2.-(viscous-coupling).pdf
?

[Hamfist]

Is this same as VC http://www.volvoxc.com/0/resources/how-to/pdf/2001-volvo-v70-xc-awd-l5-2.-(viscous-coupling).pdf
?

No it's the whole rear diff assembly.

[pbierre]

I'm confused. The rear differential is a passive gearbox in the transverse rear axle - it has no electronics. It's closer to the rear left wheel. This rear diff gearbox
has the job of allowing the two rear wheels to rotate at different speeds while going around corners.

The Haldex AWD coupler is at the back end of the propeller shaft, and does have computer interface. It has the job of responding to any slippage in the front wheel drive,
and "clutching in" the rear wheel axle to deliver power in response.

It sounds like you replaced the Haldex??

What were the initial symptoms?

[gtacs]

Did you put the Haldex (electronic box) that was with your car originally in with the new differential? Or did you get a new Haldex unit with the new rear end? Some people remove the drive shaft and convert this to a FWD car. I'm wondering if you did this would your problems go away or are you fighting multiple problems? I'll look at VIDA later and post the instructions if you need them.

[Xheart]

https://youtu.be/uZNC06Z7imQ

[vtl]

If you read the codes with DiCE/VIDA and you see CEM-1A64 "Communication with AOC control module. Signal missing", even in a yellow state, you need to take DEM (Haldex control module) apart and see if it can be fixed. Noises from DEM causes software malfunction in TCM (transmission module), without TCM there's no immobilizer quorum, engine can't be started. This was sporadic in my case.

There's a weak seal around connectors that eventually fails and let dirt/water to get in. Depends on how lucky you are, you may be able to fix your DEM. Otherwise get a working donor DEM, take it apart, clean, seal with fireplace sealant (it remains flexible after drying and tolerates high temperatures). Don't seal 3 little holes between sockets!

https://a.d-cd.net/egAAAgKXaOA-960.jpg

https://a.d-cd.net/SwAAAgKXaOA-960.jpg

https://a.d-cd.net/KQAAAgKXaOA-960.jpg

https://a.d-cd.net/5QAAAgKXaOA-960.jpg

https://a.d-cd.net/KwAAAgKXaOA-960.jpg

https://a.d-cd.net/1QAAAgKXaOA-960.jpg

[ssicarman]

Annnd, the diff won't work. Many codes in the dash from brake failure, to transmission errors to engine electrical...

Rear tires won't turn at all.

Just like my stereo install, I did not disconnect the battery before unhooking the diff and installing the new one.

I'm guessing I gotta get that vida and proceed with that.

Is the driveshaft/propeller shaft turning?

[Hamfist]

Is the driveshaft/propeller shaft turning?

The whole assembly, from the coupling for the driahaft to where the axles plug in.

The driveshaft spins, yes.

We swapped nothing external or internal on the assemblies, just dropped the whole assy, and installed the new on, hooked the driveshaft back up and put the half shafts in, and suspension arms, etc.

We did just take the coupling out of the old one and was going to swap a known working one out of the car, (diff was growling, ring, maybe pinion, not sure) into the new(used) diff assembly, but I thought software issues might be first, instead of more skinned knuckles.

[Hamfist]

Update, just hooked negative back up after a day. All messages but brake failure are gone. However, now the tachometer dropped to zero and the dash says it's in park, but the shifter says it's in reverse. The engine revs in drive and barely moves, unless you select a gear. Reverse works fine. Speedo inop too.

Ugh, what now?

[Hamfist]

Update, just hooked negative back up after a day. All messages but brake failure are gone. However, now the tachometer dropped to zero and the dash says it's in park, but the shifter says it's in reverse. The engine revs in drive and barely moves, unless you select a gear. Reverse works fine. Speedo inop too.

Ugh, what now?

Think I found something. After researching the lost comm codes and p0571, I decided to check out the DEM on the diff. It's different that the original.

The used diff and DEM had lots of aluminum corrosion on the mounting surface, I cleaned that. Also, the used one had bent pins! Also was missing the copper windings the original had.

Installed original DEM, comm codes gone, but brake codes remain.

Disconnected battery first :p

[Hamfist]

Well, all comm codes gone, did a few test drives, no return of old codes. Lesson learned, disconnect batter before any work with electrical.

However I don't think the AWD is working. I came to a complete stop and jammed on the gas. Front tires spun forever and rears never kicked in! On the dirt and pavement, same result, then sometimes, I would repeat and it would take off with no spin.

Ugh, tomorrow is another day, I'll put it up on Jack's tomorrow and run it and see what happens.

[hoonk]

However I don't think the AWD is working. Front tires spun forever and rears never kicked in!

Did the haldex unit/DEM work before you replaced the Differential? Haldex/DEM failures are common and can be $$$ to fix. You can't really easily test the haldex electronics/clutch by running the car off the ground. The system gets confused if all the wheels are not turning at about the same speed and won't engage. This is where VIDA or a scan tool that can talk to the DEM is needed.

[Hamfist]

Did the haldex unit/DEM work before you replaced the Differential? Haldex/DEM failures are common and can be $$$ to fix. You can't really easily test the haldex electronics/clutch by running the car off the ground. The system gets confused if all the wheels are not turning at about the same speed and won't engage. This is where VIDA or a scan tool that can talk to the DEM is needed.

Yes, the AWD was working, but the old diff was howling, bad bearing from being run low on gear oil. So we swapped the whole assy, and as noted above just put the old haldex unit on the new/used diff to hopefully cure the massive amounts of network issues, and it did.

I tried to post pics but it fails for some reason.

[Hamfist]

Scanned today. Dem-0007, faulty pump. I guess I'll move it from the old carrier unit... Already moved the Dem, should have just moved it all when we swapped out the rear end, lesson learned. I know it all worked on the old one, just a bad bearing. Ugh

[hoonk]

Scanned today. Dem-0007, faulty pump. I guess I'll move it from the old carrier unit...

Hopefully the faulty pump did not fry your DEM

[Hamfist]

Hopefully the faulty pump did not fry your DEM

No other codes, we will see! Doing the swap after lunch

[Hamfist]

No other codes, we will see! Doing the swap after lunch

Well, put the pump in and that's still there. Now we have DEM-
0007 and DEM-000B

All the parts from the known working rear end are swapped.

The sweedespeed threads are suggesting the temp/pressure sensor In the Dem housing. �� And the pump, new filter and fluid.

I wish I could find a good tutorial on how to activate things and test the pump or read the sensor.

[hoonk]

I wish I could find a good tutorial on how to activate things and test the pump or read the sensor.

Have you seen these?

https://xemodex.com/us/knowledgebase/dem-pump-test-flowchart-s60awd-xc60-xc70-and-xc90-2005-2010/

https://xemodex.com/us/knowledgebase/dem-flow-chart/

[Xfingers]

I just ordered the temp/pressure sensor. I've been getting multiple DEM-007 codes and AWD not working in VIDA. The frozen values in VIDA show a difference in temperature readings between the ambient/outside and internal (can't remember exactly how they're labeled). In one case, it was 40C vs. 35C; in another it was 20C vs 10C. I think that's what triggered the code. At any rate, I guess the temperature part of the temp/pressure sensor is faulty. Hopefully, replacing the sensor will give me AWD.

I know there's a thread on here on how Haldex works. I'm not sure if it explains why the temperature is critical to the Haldex operation. VIDA gives a separate reading for the Haldex OIL temp. My 2002 didn't have a Haldex unit and the AWD performed very well in the snow. But this Haldex 3 is obviously supposed to be an improvement. Maybe it engages AWD faster.