XC90 rear differential replacement - questions

ylwgto · Post by **ylwgto** » 11 Apr 2023, 11:30

I am going to replace the rear differential (final drive) on my AWD 2009 XC90. I had the whining noise during decelleration diagnosed as a bad pinion bearing. 140K mile son car.

I bought a complete (warrantied) used diff + Haldex unit from an 84K donor car and will soon replace both axle seals and the pinion seal myself. To do this I need to separate the Haldex from the diff, but I do not know what the seal between these two components is (is it an o-ring or a gasket?).

I intend to use my existing Haldex, as I know it functions perfectly and do not have a history on the donor Haldex. Is there an additional service I should do to my existing Haldex unit while everything is apart? If so, what parts are needed for that? Is it an easier instal to not have to remove the haldex unit from the car (i.e., no need to disconnect the prop shaft) and only replace the carrier?

Main question is what goes between the haldex and diff housing to seal the system (part number would be excellent).
Do you have to re-allign the car after replacing the rear diff?

thanks!!

Post by **pgill** » 11 Apr 2023, 15:22

Land Rover has a rebuild kit.

You are asking about the last item on the list.
(I don't know the VOLVO part number)

Outer pinion bearing - Timken 30206
Inner pinion bearing - Timken HM88649/HM88610 (Optional)
Collapsible spacer - LR023443
Retainer nut - LR050541
Pinion shaft seal - LR023442
Output shaft seals 2x - LR023440
Diff housing seal - LR030846
Diff to haldex seal - LR002888

https://www.freel2.com/forum/topic29814.html

Good luck

Paul

chitownV · Post by **chitownV** » 11 Apr 2023, 17:28

Are you talking about #15?
https://www.volvopartswebstore.com/show ... odel=11985

If you look here, you can see that seal
https://www.ebay.com/itm/144635431777?m ... media=COPY

As far as an alignment, if you unbolt or loosen anything that has rubber, you should get an alignment: rear subframe, control arms, etc. Also, any control arm you unbolt, it should be re-bolted and torqued with the vehicle load. You can bolt it at first, but a tiny bit loose, then do the final torque with load. If you need more room, you can drive onto 2x8 boards for that extra 1.5” of room or tell the alignment shop which control arm bolts you loosened so on the alignment lift, they can re-loosen, roll the vehicle fore & aft, then torque. The subframe does not get torqued on load.

ylwgto · Post by **ylwgto** » 11 Apr 2023, 17:58

Awesome!!! thanks pgill chitownV

Regarding my Haldex (140K mikes)...is there anything I should do maintenance-wise to it while the 2 units are apart and accessible?

Thanks!

chitownV · Post by **chitownV** » 11 Apr 2023, 18:13

I would recommend researching the seals leading to the DEM & sealing plate as well as the sensor & solenoid seals. Xemodex and others have great YouTube videos on this. All little things which could prevent something more expensive down the road.

Good luck with the work!

Here is a video to get you started:

ylwgto · Post by **ylwgto** » 12 Apr 2023, 12:24

Ok, planning to replace the pump filter on the Haldex for now.

Follow up question I'm worried about:

I looked up specs for the 2008 V8 AWD (donor car) vs. 2009 3.2 R type AWD (my car) and am noticing that all aspects of the transmission and post-engine drivetrain are identical EXCEPT the "final drive axle ratio", with is different only on the R-Design (4.06 vs. 3.33).

2008 V8 2009 3.2 R
First Gear Ratio (:1) 4.15 First Gear Ratio (:1) 4.15
Sixth Gear Ratio (:1) 0.67 Sixth Gear Ratio (:1) 0.67
Transfer Case Gear Ratio (:1), Low - TBD - Transfer Case Gear Ratio (:1), Low - TBD -
Trans Description Cont. Automatic, Trans Description Cont. Automatic,
Fourth Gear Ratio (:1) 1.16 Fourth Gear Ratio (:1) 1.16
Final Drive Axle Ratio (:1) 3.33 Final Drive Axle Ratio (:1) 4.06
Trans Order Code NA Trans Order Code NA
Second Gear Ratio (:1) 2.37 Second Gear Ratio (:1) 2.37
Reverse Ratio (:1) - TBD - Reverse Ratio (:1) - TBD -
Trans Description Cont. Again Geartronic Trans Description Cont. Again Geartronic
Fifth Gear Ratio (:1) 0.86 Fifth Gear Ratio (:1) 0.86
Transfer Case Gear Ratio (:1), High 1.00 Transfer Case Gear Ratio (:1), High 1.00
Trans Type 6 Trans Type 6
Third Gear Ratio (:1) 1.56 Third Gear Ratio (:1) 1.56

Does the rear diff have to match the front transfer case ratio (like on 4x4s)? I assume the R-Type has a slightly higher ratio to help with acceleration, which I do not need, but did I screw myself over here? I'd hate to install a unit that doesn't match the front transfer case ratio and mess things up.

chitownV · Post by **chitownV** » 12 Apr 2023, 12:58

The angle gear is engine specific for 3.2 or V8. Though there is a rear coupling (AOC), the angle gear ratio should match the final drive ratio. IIRC, all 3.2s have the same rear diff, final drive ratio.

ylwgto · Post by **ylwgto** » 12 Apr 2023, 13:27

Thanks

From what I'm reading the transfer case gear ratio (is this the angle gear?) ratio is the same between the 3.2 and all V8s regardless of R design sub-model (always listed as 1.00).

volvocars.com lists the same part number (36050629) for the differential across all xc90 v8 (2005-2011) and 3.2 (2007-2014) despite the fact that there are indeed different angle gear part numbers for the V8s and the 3.2s.

EXCEPT there is no differential part number or angle gear part number listed specifically for the R-type 3.2 (the 3.2 R-Design is the only model with the 4.06 rear diff ratio)

Do you have info on how the ratios differ in the angle gear between the model sub-types?

If the angle gear ratios between all models are indeed identical (as I'm reading, despite part number differences) then the AOC simply overcomes the ratio difference between 3.33 (3.2 and V8 models) and 4.09 (3.2 R-design models). Could that be true?

chitownV · Post by **chitownV** » 12 Apr 2023, 14:58

I haven't had to jump into the angle gear (transfer case) nor the rear diff. Remember there are a lot of aggregated specs that have filled data, meaning if their software or a person couldn't find the data, they might fill it with data from a different engine. Doing a part search from Volvo, the angle gears are specific for each engine. Perhaps that's because of the mounting. Remember, we have big debates just on the correct transmission fluid listed by Volvo, lol

A couple of concerns.
- You said you will keep your Haldex Gen 4, which is different than a 2008, Gen3, system. They should bolt on and be interchangeable.
- If you change the rear axle final drive ratio, you have to ask yourself if the DSC, DEM, traction, etc. will be affected by a different rear axle ratio. The hope is that it shouldn't, due to the ABS wheel speed sensors reading the same, but who knows if engagement/disengagement is different or behavior is different after wheel spin.

Again, I can also see online (minus Volvo's US website) the shorter final drive ratio in the early 3.2s as well. I think I did see it on a Volvo (dealership?) UK website. If I were you, I'd call the dealership and see if anyone in parts could look up specific parts for the angle gear and rear diff with your VIN and come up different than the Volvo website.

Are you fixed on an earlier V8 diff? Have you done a search for your specific diff part number? If you don't have it, maybe the dealership can help with your VIN.

Good Luck!

ylwgto · Post by **ylwgto** » 12 Apr 2023, 16:12

Thanks for the feedback, chitownV. Good point about internet databases being inaccurate and/or incomplete. is there a way to look all this stuff up in a volvo database like VIDA or something?

I guess I have to call a dealer and try to find out more from them (was hoping to avoid that).

My issue is I've already purchased the 2008 diff...only after did I begin to worry about gear ratio differences when it dawned on me they might be different between models.

I've already separated the Haldex from the diff on the donor part. The diff is purely mechanical and a pretty simple part (just a pinion gear and axle output). The Haldex unit from the donor part shares the same part number as the Haldex in my car. I can't see how (although i am no expert) a different gear ratio in the differential would impact any of the car's electrical systems (DSC, DEM etc), but who knows.

My main concern is that a different ratio rear (lower in my case) wouldn't play nicely with the angle gear ratio and somehow mess up the AWD system or transmission. But it seems the AOC would account for this by altering the pressure accordingly in the rear when the AWD is engaged...

Anyhow, if anyone else has some advice on this I'd GREATLY appreciate it.