tub drain - trap replacement?

Hi- question about a tub trap replacement... I believe the plumbing under the tub to be original to the house (1963). I have replaced quite a few old plumbing fixtures and the tub trap is next on the list. It suddenly stopped draining and I can't work the pipe snake through this trap:

My question is basically- can I just cut through the galvanized pipe on both sides of the old trap and insert a new trap with some kind of splice to each galvanize pipe? Please advise, I am novice.
Many thanks,
jeremy

I'm not a pro, either, but I think that is a drum trap...and if it is, you'd never get a snake through it; it is also no longer approved, so replacing it with a new P-trap is a good idea. It doesn't look like it is vented, either, so to do it right will take more than just replacing that old trap with a new one. But, if you cut it off, you could use no-hub connectors and PVC to install a new trap in place. WIthout a vent, you risk siphoning the trap, which will open the drain to the sewer and any resulting smells, gasses, etc. If you local authorities allow AAV (air-admittance valves), you may be able to run that up behind the tub wall above the top of the tub (above the flood rim by at least 6"). But, since they can fail, they must be accessable for eventual replacement (normally takes many years, but still).

hmm...that looks like a modified bottle trap to me. I am pretty sure they are not acceptable in any code now for a number of reasons. So long as the trap arm going to the right actually goes to a proper vent stack, you are fine to just cut out the sections and splice in a p-trap. However, since you have a nice open crawlspace, I strongly urge you to replace the entire tub drain all the way back to the main stack. You will find, that once you open up galvanized piping as old as yours, that it is fairly choked up inside with corrosion, and you are better off replacing as much of it as you can.

From the looks of it I would replace all the galv. and the trap, that pipe is probably nothing but rust inside

It is a drum trap, which has been "modified", probably because someone had a problem with the original plug for it. To snake that one, you just have to remove the "test cap" on the bottom,(either loosen,or cut, the hose clamp), and send the snake up into the outlet pipe, then get a new "GemCap" test cap to seal it again. The more difficult way would be to cut the galvanized piping and insert a new trap. Whether that would tax your DIY skills is something we cannot tell. But you would probably still have to snake the line.