Transfer box service query

[StuBeeDoo]

I'm getting my F25's transmission serviced next week. This will be the second time in my ownership. When I bought the car it was 5.5 years old and had only just come out of the dealer network, so the nothing within the drivetrain would have been touched at all for the life of the car which by then had done 72k miles. While the car was at the ZF-approved service centre I also had them change the fluids in both diffs and the transfer box.

Fast forward to now, and the car has done 34k miles and gone 4 months beyond ZF's recommendation of 3 years between transmission services. Personally I don't think it necessary to change the diff fluids this time, particularly as they aren't limited-slip. But what about the transfer box? Do you think its fluid should also be changed every time the transmission is serviced? I don't suppose it will add a great deal to the bill when I'm going to be spending over £500 in any case.

[Alan Gunn]

Didn't have the transfer box oil changed when i had the auto box serviced at 157k i think it was when i got the car.
But i bought a Ltr of the oil and did it myself very easy to do.
Don't think any had been done in it's life before i got the car.

[StuBeeDoo]

The job was done today. I asked how often they recommend to change the transfer box oil and they said they recommend (but don't insist) the transmission, transfer box, and diffs are all done at the same time, every time. I.e every 3 years or 50k miles.

But they would, wouldn't they?

.........And I went along with it.

[X5Sport]

I thought ZF recommended 8 years or 60,000 miles? My local Indy will do the gearbox for about £450 incl parts. Need to ask him about the diffs etc. the X6 has a three chamber rear diff, each with their own oils and those are of two types. Front looks easy but the transfer box has a support member right where the fill & drains are so needs to be moved. He may have a trick to get round that (I hope).

[StuBeeDoo]

I thought ZF recommended 8 years or 60,000 miles?

I think I only once found the information on a ZF website, and I can't find it again now. I seem to remember that I posted a link to it here when I had the job done in July '18 but TBH I haven't gone to the trouble of trawling through all my posts.

There seems to be plenty of "information" on the web relating to service intervals for the 8HP series of 'boxes. The recommendations vary wildly from 100k miles downwards to 60k kilometres. Some sites also append the mileage with ".....or no more than 8 years". There are also reports of independents saying stuff like "as soon as it is out of BMW warranty".

Personally I'll stick to my transmission specialist's recommendation. The £640 I paid yesterday might seem a lot, but spread over 3-and-a-bit years it's not so bad, and it's certainly a lot cheaper than a rebuild or a replacement. ........And if I have to go to them because of a transmission issue, at least they'll have their own record of the servicing I've had done and not be able to claim that whatever caused the issue was down to neglect on my part.

[X5Sport]

It’s not a bad price for everything. It’s definitely a task on my list. The X6 has only done 53k but it’s 11 years old so on time alone probably ‘a good thing’ to get it done.

[Alan Gunn]

That 8 year or 60k sounds familiar.

[hennabm]

My 2011 3.0d was suffering from a bit of judder on take off, if in either lock. It was diagnosed as the transfer box. The recommended remedy was to replace the oil and then reset the car.
Believe it or not this has cured the judder.

I had my transmission oil changed at 90k, very soon after buying the car. IIRC ZF recommendation is 80k,