I did the struts in my S70 last weekend, which I assume is pretty close to the 850 in terms of what needs to be done.

The special tools called for on the S70 are 999 5467 which is used to unscrew the strut mounting nut, 999 5469 which is used to hold the star shaped shock absorber retaining nut, and 999 5468 which is used to hold the end of the shock piston rod in place.

I did not use any either of these tools. I took off the strut mounting nut with an electric impact wrench. I took off the retaining nut with channel lock pliers.

The strut I put back on was from Bilstein. It uses as standard allen key to hold the end of the piston rod in place so 999 5468 wouldn't even apply. I tightened up the retaining nut as much as I could using an allen key on a 1/2 inch ratchet and the channel lock pliers again. I tightened it up really well, but probably didn't meet the torque spec (I doubt it matters so much). I then put on the strut mounting nut. I put the allen key on my torque wrench and a big adjustable crescent wrench on the nut. Once it got tight, I used the torque wrench to bring it to the torque specification.

The one specialized tool you will need is a good set of coil spring compressors. Get the kind the positively lock to the coil (a pin extends to keep the compressor from slipping off). This can be a dangerous job. Be careful. Don't put your head above the compressed spring ever.

-Ted