Rear differential oil change?

[3C4M Guy]

I plan to do a DSG and Haldex service soon for my 4Motion. It would be convenient to change the rear diff oil at the same time. However, the literature I've read suggests the diff oil never needs replacing. What are the thoughts of R36 enthusiasts? Change it or not after 15 years? The specs say 1 litre of G 052 145 S2? Is it exactly 1 litre? Also, does the drain plug have a captive washer requiring replacement of the whole plug? Thanks.

[Crusty]

I’d change it. Easiest part of all three you’re doing.
I can’t recall on my old sedan but I believe it is about a litre. Very easy job, hardest part, getting the fluid in there.

I used a squeeze bag and jerry rigged a 6mm (I think it was 6mm) clear tube as the gravity feed option was a PITA.
Be easier if you had a second pair of hands though.

[kamold]

Yes I think it's a good idea to do the front and rear diff oil.
1L each.
From memory yeah sump plug has a washer like a regular oil sump plug. M10x10 I think but don't quote me on that.
You can just use a suitably sized copper washer if you can't get the replacement drain plug.

[Dinogzav]

The washers aren't really critical to replace just best practise. Check the Nulon squeeze bags. They come with a tube and make the job very easy. Did my Grand Cherokee front and rear diffs as well as transfer in about 10 minutes.

[Crusty]

Nulon squeeze, that’s what I used!

[3C4M Guy]

Many thanks to everyone for your advice

[3C4M Guy]

Yes I think it's a good idea to do the front and rear diff oil.
1L each.

There's a front diff as well that's separate from the DSG?

[MIG]

There's a front diff as well that's separate from the DSG?

Yep, VW calls it the bevel box; probably a good idea to do the Haldex filter while you are there too, depending on what generation unit you have.

[3C4M Guy]

Yep, VW calls it the bevel box; probably a good idea to do the Haldex filter while you are there too, depending on what generation unit you have.

Thanks MIG. I'll do the bevel box at the same time. It looks like it takes the same oil as the rear diff. It seems the drain and fill plugs might have captive washers requiring new plugs.

Mine is a Gen 2 Haldex and I've got a new filter ready to go. I won't re-use the washers this time. Again, they might be captive.

[3C4M Guy]

Well, I finally got around to doing this job. The old DSG oil looked in very good condition and was visually similar to the fresh oil. However the Haldex filter was filled with blue-grey sludge. This sludge was even in the thread of the fill plug.

The Gen 2 Haldex filter 02D 598 574 comes in two parts and I was surprised that the two parts of the new filter had been assembled with the spring under the cap and the shaft with the O ring at the base. When I did the job 5 years ago, I installed the filter with the spring at the base.




I was now confused, so I searched the net and discovered that very few places such as the ECS Tuning web site show the spring at the opposite end to the cap. I think I copied this image when I changed the filter last time.


Most web sites show the filter in two parts. However where the parts are pre-assembled, the majority show it this way with the shaft and O ring at the base. I've now learnt that this is incorrect! Assembling this way makes the filter longer and it will not fit in the housing.


Take note if you ever do the job yourself.