Hi,

I’m hoping someone can help me with a question about my 2012 Kia Sorento diesel (6-speed automatic) — I’ve been maintaining it very well and it’s done 763,000 km on the original engine and gearbox (which has ~550,000 km on it), so I’m pretty proud of how it’s held up.

I recently replaced the front right-hand drive shaft — it was defective, and I only noticed it after the warranty expired. I’ve replaced this shaft once before (about 1–1.5 years ago) due to a leaking CV boot, but that replacement was also defective. I’ve just installed a brand-new one today, and the clunky noise I’d been experiencing has gone — I’ll drive it for a while to confirm, but I’m confident it’s fixed.

However, the mechanic mentioned that the teeth of the old drive shaft look slightly abnormal and don’t have any oil — which made me realize I’ve never serviced the transfer case. It’s been almost 400,000 km since the last oil change.

Now I’m a bit nervous — should I drain and top up the transfer case with fresh oil, or could this cause damage? I know that if you don’t change gearbox oil for a very long time and then top it up, it can sometimes cause issues (though not always). But the transfer case on my car has its own separate oil pan — completely separate from the gearbox — so I’m wondering whether this is a safe procedure or if I risk ruining the transfer case and making my car undrivable.

I’m located in Canberra, Australia, and plan to get the oil changed sometime next week (Thursday if possible). Any advice would be very appreciated.

Thanks so much!