I have 14 x Snap on tools 18 and 14 volt impact guns for sale, they use variable trigger to feed a high speed motor that drives into a planetary gear box that then drives an impact mechanism.

The part numbers are:-

ctu8850, there is one of these, it makes over 650 ft lbs
ctu6859, there are six of these, they make 480 ft lbs
ctu4410, these are 14 volt, there's 6 of them, I think they make about 280 ft lbs
ctu3850, I think this is 12 volt, I don't know the spec, its as old as time.

All of these tools ran on ni cad batteries that Snap on don't produce any more, I took them all as trade in's against newer models, I never got around to selling them and I cant bring myself the throw them away.

I'd take £100 for the lot, but you'd have to pay the post as they're all over a kilo each.

If you need any more info, let me know and I'll do my bet to help.