I know I have seen posts saying stay away from the 2001 s60/v70's. I am not sure why? I assume because it was the first year of the platform that it had some issues? I am considering buying a S60 in the 01-07 range, but what are the preferred years and why? I have an 04 V70 which I like, and I don't want to take on a car of an undesirable year in exchange for my car.

The 2001 is undesirable because of the Magneti Marelli electronic throttle. Having said that, mine is still working fine at 187 000 km (about 116,000 miles), with the software change.

My car has a manual transmission, so no issues there. The repair issues have been fairly typical - weak OEM swaybar endlinks, CV joint boots, a wheel bearing, some light bulb/socket issues, an A/C compressor clutch air gap issue (fixed it myself by disassembling and re-shimming) and a PO045 code (evaporative emission control system leak) that I can't be bothered to correct. Otherwise, it's been maintenance. I've been quite pleased overall. However, I couldn't guarantee that anyone else would have the same experience.

I recently bought a 2004 S60 NA. I currently own another 2002 S60 NA. The difference between the cars is night and day. he 2004 is appointed a bit nicer and the transmission shifts smoothly, substantially better than the 02. The 2002 has the dreaded transmission problem. I have an extended warranty and am just waiting for the transmission to go so I can get it fixed. Go or an 04 or later. Sorry don't know about the 03's.

Hopefully someone will know if the 03 has the pos transmission like the 01 and 02's.

they all have the same transmission. The software is changed and there may be some internal component changes, but they would be minor
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1998 V70 AWD->FWD->AWD Turbo 215k+