2006 XC70 rear diff leaking Topic is solved

Rvolvos · Post by **Rvolvos** » 01 Feb 2023, 20:07

The rear diff is leaking from the bottom of the housing. The leak point almost looks like check valve from the AOC part of the differential. It lost a lot of fluid all at once.
Does anyone recognize what this is and If it can be fixed? The leak is just in front of the sway bar, as seen in the picture. Edit found a picture on EBay.

The irony is I noticed the rear diff was leaking from the right rear drive shaft. It was low on fluid with a lot of metal particles in the remaining fluid. Removed the old fluid put new one in with ATP-205 (from the rear fill plug) and it’s no longer leaking from the seal. Now this, I can’t win

Post by **jonesg** » 02 Feb 2023, 07:52

Is it a vent ? it might be over filled.

Post by **xHeart** » 02 Feb 2023, 08:44

jonesg wrote: ↑02 Feb 2023, 07:52 Is it a vent ? it might be over filled.

Th oil inside FD heats up, vent helps, but without nipple and valve collects dirt; items 16 & 17.

An overfilled Final Drive will drip on exhaust pipe; you'll smell it burn. The fill procedure takes, fill, drip, and then a draw out 100ml when on level ground -- the capacity of our 2001 V70XC FD with VC is 450ml. There is no fluid where rear axle slides in, but you can replace the axle shaft seal. Using Liqui Moly Assembly Lube for metal-to-metal has worked for me.

This may help > viewtopic.php?t=95373

Rvolvos · Post by **Rvolvos** » 02 Feb 2023, 09:22

jonesg wrote: ↑02 Feb 2023, 07:52 Is it a vent ? it might be over filled.

The vent is on top, the hole in the picture is at the bottom.
I will recheck both fluid levels.
Thanks

Rvolvos · Post by **Rvolvos** » 02 Feb 2023, 09:34

xHeart wrote: ↑02 Feb 2023, 08:44
jonesg wrote: ↑02 Feb 2023, 07:52 Is it a vent ? it might be over filled.
Th oil inside FD heats up, vent helps, but without nipple and valve collects dirt; items 16 & 17.

An overfilled Final Drive will drip on exhaust pipe; you'll smell it burn. The fill procedure takes, fill, drip, and then a draw out 100ml when on level ground -- the capacity of our 2001 V70XC FD with VC is 450ml. There is no fluid where rear axle slides in, but you can replace the axle shaft seal. Using Liqui Moly Assembly Lube for metal-to-metal has worked for me.

This may help > viewtopic.php?t=95373

I checked the vent with a mirror, it was dry. Is it possible to replace it without dropping the sub frame? But it does leak on the exhaust.
I have a newer style Haldex system, it uses the 80 bar pressure sensor instead of the 40 bar.
I did remove the 100ml afterwards from the rear diff.
I did find and read the post in the link, perhaps the seal to the aoc is leaking? Need to check both levels.
Thanks much!
Are you sure that no gear oil can leak from the rear axle seals?

Post by **xHeart** » 02 Feb 2023, 10:05

You can lower the FD by turning the bolt #14 to access and service just the air vent valve.

I also lower and support the prop shaft at the u-joint while working at 9, 2, 3 & 8 to help FD/VC lower with ease. You may want to pull the exhaust to one side a little by sliding off the rubber at the anchors. Raise the rear wheels on ramp if not on jack stand.

Rvolvos · Post by **Rvolvos** » 02 Feb 2023, 21:44

Thanks much, will be looking into this when back from my business trip.

Rvolvos · Post by **Rvolvos** » 19 Feb 2023, 18:08

I checked the AOC fluid level , it was still below the drain plug which leads me to believe that the differential fluid did not migrate into the AOC fluid.
I removed the remaining differential fluid there was only 350ml left and still leaking.

I lowered the rear differential with the car on ramps. Dropped the exhaust, lowered the sway bar, removed the plastic bracket underneath the rear diff and removed the only bolt that hold the rear diff.

This gives enough space the remove the rear diff filter as mentioned by Xheart. I was able the insert a t-pin into the bleeder nipple. The filter was dirty and difficult the blow through so I added an atf hose over the bleeder nipple and with a hose clamp as a temporary vent.
I was able with a transfer pump to remove air, I also noticed air is being pulled into the hole in the bottom of the rear diff. But I was not able to add air into the rear diff through the hose.
Added 500ml gear oil and took it for a test drive, unfortunately it is still leaking

Does anyone has a clue what is wrong?

Attached some pictures of the lowered rear diff.

Rvolvos · Post by **Rvolvos** » 05 Mar 2023, 13:34

Contemplated converting it to FWD but ended up buying a low milage rear diff from a 2007 XC70 on eBay. Currently in the process of removing the rear differential from the car.

Rvolvos · Post by **Rvolvos** » 15 Mar 2023, 21:57

While waiting on parts I disassembled the rear differential. To my surprise the bearings and gears were in excellent shape. Also the AOC oil was clean. Unsure where the source of the the noise was.
After disassembly I learned that the differential has a pinhole vent on the back. The AOC has the vent with the breeder element on top as shown above. See pictures below, holes are marked.
I purchased this tool on Amazon to remove the crown wheel: Fuel Pump Removal Adjustable Wrench Spanner from 3/8 inch to 1/2 inch, Fuel Pump Lid Tank Cover Kit, Fuel Tank Lock Ring Tool https://a.co/d/3cAhEH2. See attached picture. Grinding the corners of the teeth will increase engagement.
The openings around the bevel gear do connect with the hole on the bottom of the rear differential, where the fluid leaked out.
I can blow through the new breeder element, but nut through my old element, cleaning made no difference