Took my F54 in for its normal service and the dealership noticed that my transfer case is leaking oil. I tossed the car up on the ramps to take a look and sure enough it is.

They're fixing it under warranty (will find out this week whether 'the fix' involves just changing out the driveshaft seal that failed, or a whole new transfer case).

It seems that the transfer cases for manual transmissions (what I have) and automatics is not interchangeable, which is a bummer. Plenty of rebuilt/resealed AT cases available, don't see anybody that sells the MT part number other than new from the dealerships.

I wonder if anyone knows how complex an operation it is to DIY? Since my warranty is expiring soon, and anecdotally the cases do seem to develop leaks, and of course dealership work would be a fortune (if I wasn't under warranty), I wonder what I'll be looking at if the case starts leaking again.

It looks like just removal of driveshafts, unbolt the case, mate a new/refurb unit (or replace seals, none of which are very expensive), mate back up, re-install driveshafts...but has anyone done it? Basically wondering if there is any weird disassembly that I'm not thinking of (like, does replacing the case involve dropping the whole transmission off the engine -- if so, ugh!), whether there are computer modules that need to informed of changing out the case, etc etc. I don't see anything that looks like a wire plug on the case or the photos of it online but I don't know what I don't know. Appreciate anyone that's done it!

 

Not much of an update, but the dealership has told me that they are just going to replace the entire transfer case.

Kinda neat! But also would be $$$$ if doing it out-of-warranty. The cost of the case is ~$3500 from MINI, and then 5 or so hours of labor to remove and install (my estimate, so dealer might bill at 10 hours?).

I snagged the PDF 'official dealer service manuals' for the clubman all4, and it looks like removal and re-installation of the transfer box is pretty straightforward, EXCEPT that under "installing exchange transfer box" it says "Carry out coding/programming." as a final step. With no actual details on what is involved in that.

If anyone has ESYS/ISTA installed could they see if there is actually a service routine for doing a transfer box exchange? I doubt we'll get an answer as to what this actually does (my wild speculation, perhaps it de-rates the engine's power for a few hundred miles? Or changes the method of engaging the rear wheels for a few hundred miles? so that the new transfer case can break-in...).

I still have never seen a good explanation for exactly how the transfer case functions, the teardown of the Gen2 All4 case I found on youtube had the mechanic stumped too.

 

I wonder if you would get more replies over on the Countryman side. All the hard core off-roaders abusing their transfer cases, lol. Seriously, more AWD cars over there maybe?

 

Hah. Yeah I don't off-road with my Clubman or any of its 6.0 inches of ground clearance glory. I guess the countryman with its 6.5 inches of amazing ground clearance is the true rugged off-road machine ;-).

Probably a good idea about crossposting there though. The transfer cases are the same in the two vehicles. Ahem, I guess MINI calls it a "transfer box". Still wish I understand what it was really doing, mechanically, inside.

Funny though, I own a 5th gen Ford Ranger now and apparently there are a few people with transfer case leaks on those trucks too. Mo' differentials, mo' oil seals, mo' problems, I guess. I'd mostly be comfortable swapping the transfer box in the Clubman myself at this point, except I'd like to understand the ISTA coding procedure/what it actually does/if it's actually needed. Thankfully I have my warranty to lean on for now. And of course finding a source for a rebuilt one would be swell down the road, since new from MINI they are a small fortune.

 

I too can’t imagine what kind of programming the car would need. The transfer case itself is such a simple thing. No electronics - just a set of gears I believe. If it was my car and wanted to DIY a new transfer case, I wouldn’t bother 😄

I'm looking at the (unofficial) TIS and it’s fairly involved, but kinda basic car stuff. Except the front of the driveshaft. It threads into the transfer case somehow. I can’t quite wrap my head around it from the pictures and description. There’s lots of Warnings about not messing it up though or you’re damage the transfer box. My version also doesn’t mention programming the transfer case…

Every time I’ve changed my oil or serviced my transfer case oil (twice now. I’m at 75,000 miles / 120,000km). It does have a thin coat of oil/dirt on it. I’m not too concerned though. I’ll just keep doing routine service on it (and the manual transmission) to make sure it’s topped off. I use Amsoil Synthetic Severe Gear 75w-90

Reminds me of an old BMW E36 of mine that leaked power steering fluid. I could have replaced the rack, but topping-off with $1 in power steering fluid every month was much cheaper and easier!

 

An update quite a lot later:

My dealer was not super communicative with me but the problem ended up being a CV joint spewing grease, apparently.

The transfer box had a lot of oil residue on it. The dealer indicated initially that they would either have to replace seals on the transfer box, or replace the whole transfer box (under warranty). A few weeks after this, I brought my car in to get the brake fluid flushed. I mentioned that they were waiting on parts to fix the transfer box leak when i dropped it off, and they said they'd keep me informed about when the parts came in. At the time I dropped the car off they said they would probably just order a whole new transfer case, but it might take a while due to supply chain issues.

What I hadn't noticed was, I picked up the car and they had just gone ahead and replace a CV joint bolt (part 33-40-6-858-534). The actual work order said "customer reports a leak, inspected and replaced..." the above part number.

The odd part: I guess they hadn't wiped the transfer case clean of grease afterwards. A few weeks after the repair was done, I went under the vehicle and cleaned things up so that I could keep an eye on the leak and see how bad it was.

I was a little surprised when months went by and things were perfectly dry down there. I figured the dealer would call eventually, but given there appeared to be no actual problem, I wasn't super worried.

The other day I finally got to checking the level of fluid in the transfer box by loosening the fill bolt and dipping a lock pick in (the only thing I could find small enough to get in at a decent angle), and it was full still. So I guess I'll never hear from the dealer about that, heh. I'm mostly doing my own maintenance now (oil changes and brakes and air filters), so may not be back to the dealer for a while.

I am relieved ;-). A new transfer box is not a cheap thing, and they seldom come up for sale on ebay or other places, particularly not for All4 with manual transmission, and the whole communication is hard thing meant I was wondering whether this would still be under warranty or what.

Anyway, back to my everyday plans of keeping this car forever now, hehe. TLDR: if you see grease all over your transfer box, it could just be an $18 part and a couple of minutes of labor if it's a CV boot.