AOC Fluid Change - Or What A PITA, But....

[billr99]

Ever since I bought the new-to-me '05 back in late October I've been working thru all the various maintenance items on the official schedule plus all the other stuff not mentioned in the schedule to bring the car up to my standard. Interestingly, this car, which is a one family (but two owner) car was maintained by the book by Volvo up to about 180K kms. In fact, it appears that they didn't do a half bad job at it. But as we all know they did not do the glaring stuff that we know needs to be done, such as tranny, bevel and rear end gear, and the AOC.

I decided as the last things to do on the driveline, I would do the AOC (i.e. Haldex unit) and rear diff. At some point in the car's past life, the bevel gear had been re-sealed and its fluid was OK when drained. The tranny was dirty but not as bad as I expected considering the mileage, so I was pretty confident that the AOC and rear diff wouldn't be too bad. Plus I had no kind of DEM errors, etc. or any other signs of a non-functioning AWD system. Well, although both jobs were pretty much un-engineered PITA to do, I have to say to anyone who has at most 160K kms on their XCs and who have not changed these fluids, you better get on it. This car was at first your typical old geezers' car, then it moved into the hockey mom category. Even with that, or perhaps because of that, the fluids I pulled out of both the AOC and rear diff were best described as "grey honey". The rear diff lube hadn't thicken much past its 75w-90, but it was still pretty horrid. The AOC fluid, which is a 10w new, was unbelievable. Having to suck both out with a 1/4in tube and MityVac was glacial considering the 3C temp and the viscosity but I did manage to get nearly all of it out (about 800ml out of the diff and 500 ml out of the AOC - note that VIDA states that capacities are the exact opposite for some reason). But again, I want to emphasize that Volvo's claim of "lifetime" on both these fluids is as ludicrous as their same claim in regard to the tranny and bevel gear.

There are a few outlines on how to do these jobs around, the best being here (http://www.matthewsvolvosite.com/for...hp?f=9&t=30549), so I won't go into it. But I will recommend dropping the rear of the exhaust from its mounts as it makes getting to the fill plug in the rear diff do-able and also gives a bit more room to work for getting the fluid out, then in, in the AOC. Now as far as getting the filter out of the AOC. This is clearly one of those cases where the engineers at both Volvo and Haldex must never have had to do the job themselves (or they gave it to the new guys to design). After a couple of hours of trying out just about every possible tool my 45 year collection could offer, I bagged out. Either my ratchets/wrenches were too big, too short, or too fat; or the combination of a 5mm hex bit and gear wrench was too short to get any meat on the rusty cap screws used to hold the cover on. Didn't help that I had a sprained thumb on my left hand which seemed to be the only hand that I could get in there laying on my back under the car which was full up on jack stands). Compared to VW/Audi's implementation of the Haldex, Volvos (and Fords, btw) is an absolute screwup. Why use hex head cap screws, especially in such a limited space? For that matter why design the unit so that the filter is so buried that it really does entail dropping the pipe and propshaft if you need to be able to get ugly with the screws (which btw are about twice the length they need to be) to get them out. VW/Audi uses an arrangement somewhat similar to Volvos engine oil filter casing albeit about tenth of the size, stuck out in a decently accessible position and removable with a special filter wrench or channel-locks. In any event, I surrendered and gave the job to my local guy, who only gets the stuff I don't want to do. Took him about an hour to R&R the filter (helped by an hour time limit backed up with an offer of a 12 pack if the time was met) where he too dug deep in his tool boxes to come up with workable combinations of things to be able to free the screws, then back them out 1/8 turn at a go. Filter was re-installed using anti-seize on the screws and a bit of RustCheck to keep the screws from getting rusty or corroding themselves to the new alloy cover.

Anyway, as some of you know I've done a fair bit of work on Volvos over the last 20 years and this job has to be on the list of "The Worst" ; but despite that, the condition of the fluids demand that they be changed and probably at an interval closer to what VW/Audi recommend which, I believe, is 30K miles. As mentioned, VIDA 2014A states in Section #46 that the AOC takes about 650 ml and the rear diff about 500ml; but I got out about 500ml and 700 ml respectively. In turn, I added about 600 ml to the AOC and 800 ml to the diff and then extracted 100ml as per VIDA.

Cheers,

Bill

[Forkster]

I did the AOC and rear diff with my XC two years ago. You're 100% right - a FPITA. I remember using a small wrench holding onto a hex driver bit to get that fluffing head cap screw off. The only good news was that my car was quite warm as I did it in July and the fluid came out lickety-split with my drill vac. Wifey came out when I was cursing up a storm to see what was wrong and I explained that some arse in Ford designed the AWD system because a Swede would of had two plugs - one on top side for fill and airhole and one on the bottom for drain.

[The Landshark]

I did my '06 last year, i found it was far easier to remove the driveshaft and driven flange from the haldex unit, it only took about ten minutes,
As i was removing the hydraulic pump i had to do it anyway but i would say when you're doing the filter it is well worth pulling the pump and cleaning the screen on the pump intake, there was quite a bit of sludge built up on mine.
The filter can then be done very easily.

[billr99]

I did my '06 last year, i found it was far easier to remove the driveshaft and driven flange from the haldex unit, it only took about ten minutes,
As i was removing the hydraulic pump i had to do it anyway but i would say when you're doing the filter it is well worth pulling the pump and cleaning the screen on the pump intake, there was quite a bit of sludge built up on mine.
The filter can then be done very easily.

That was an option, but the bolts and flange on that end of the driveshaft looked to be rust-welded and, frankly, I didn't want to get into a big project unless it was the only way. Will probably have to do it some time in future as I can't expect that pump to last too long having had to pump that crud around for as long as it has. I suspect it is going to take some pretty heavy methods to get things to come apart. Once again, the trials of living within a couple of clicks of the North Atlantic.

Cheers,

Bill

[The Landshark]

That was an option, but the bolts and flange on that end of the driveshaft looked to be rust-welded and, frankly, I didn't want to get into a big project unless it was the only way. Will probably have to do it some time in future as I can't expect that pump to last too long having had to pump that crud around for as long as it has. I suspect it is going to take some pretty heavy methods to get things to come apart. Once again, the trials of living within a couple of clicks of the North Atlantic.

Cheers,

Bill

You and me both man!, i do find that a squirty bottle of acf50 applied to the underside once a year or so keeps the tinworms at bay.

[billr99]

You and me both man!, i do find that a squirty bottle of acf50 applied to the underside once a year or so keeps the tinworms at bay.

Yeah, we have stuff here called RustCheck that works really well and, in fact, this car was "professionally" done; but they didn't spray any of the actual componentry, just the under-bodywork. Now, umpteen years later, I'm playing catchup.

[8pack]

Fluid Film!