Peugeot 807 Gearbox Slipping

Slipping gears on an '02 807? Sounds like a potential headache. Have you checked the transfer fluid level and condition? Low or dirty fluid can definitely cause those symptoms. Any unusual noises coming from the transfer case, like whining or grinding?

I haven't checked the fluid myself yet. I wanted to get some opinions first. There is a slight hum, almost unnoticeable, but it's there. If it is the fluid, is it a simple top-up, or does it point to a more serious issue?

That hum isn't a good sign, I'm afraid. A slight hum combined with slipping gears and oil wear screams mechanical wear in the transfer case, likely defective gears. While a fluid change might help temporarily, it's probably just delaying the inevitable. You're likely looking at internal damage. I'd seriously consider getting it checked out by a reputable workshop before it gets worse and leaves you stranded.

Right, that's what I feared. Thanks a lot for your input; it confirms my suspicions. I've booked it in at a local garage; they've quoted me 330€ for the repair. Hopefully, that'll sort it out. I appreciate your help!