Just a quick question: I remember reading somewhere that the differential fluid should be changed from time to time (like every 100k or so, if memory serves me). Is this so? If this is true, then is it a DIY job?

Thanks.

On ALL FWD cars, the diff is inside the trans and shares the same fluid. If an auto trans and its ATF is dark, flush it on occasion.

Thanks for the info. I'm due for a tranny flush in another 15,000 miles and right now the fluid looks good.

www.volvospeed.com and then Bay 13 has a diagram of how a machine can flush it. You really don't need the machine. Look at www.ipdusa.com and click on the 850 section and you'll see a funnel, some tubing and clamps they sell. You can buy their kit or you could just go to the hardware store for what you need. The best part of the IPD site is the PDF file that tells you how to do your own flush. It's an easy procedure, and I would recommend doing this at 20-30K miles, routinely for an 850. Switch to Mobil-1 Synthetic ATF if you have a turbo and you want to give your car the best preventative maintenance. Good luck!
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.