Need a little help please. I just ripped out my old shower and I'm about to build a new shower pan. I hammer drilled up the concrete around the old drain. There is 2" drain pipe about about 5" tall which is sleeved into another larger iron pipe with a big flange on it, ( the p trap I presume). This existing 5" tall pipe is to tall when I set my new Oatey Drain on top. I thought about cutting down the 5" tall pipe but it will require taking out much more concrete to get a saw in there. I was thinking about replacing this piece of iron pipe with a shorter piece of PVC. How would I connect the PVC to the iron in this situation. I can't use one of those rubber couplers. Any ideas?

If "sleeved into another larger iron pipe with a big flange on it," is indeed the p-trap, take a screwdriver and kind of scrape away at the area where the pipe goes into the " big flange ".
This sounds like a cast hub fitting. Depending on how old the plumbing in your home is the connection between the pipe and hub will be made with either poured lead or a rubber gasket.
If it does turn out to be the hub fitting you can simply take a pipe wrench and turn your 5"piece of pipe left and right several times until it becomes loose, keep turning left and right and kinda pulling up at the same time until you twist the piece of pipe out of the hub. If the joint was poured with lead you can take the screwdriver and pry out the lead ring. After the lead is removed there will be a fiber substance called oakum under the lead. Again using your screwdriver scrape all the oakum away until you have a clean empty hub left.(Note after you remove the pipe stuff a rag into the opening left by the pipe so nothing goes down into the drain) Now if you remove the 5" piece of pipe and there is a rubber gasket remove the gasket and you will be left with an empty hub. To install the new drain you will need to locate a "2" service weight hub gasket". Some places may call them a soil pipe gasket, or just a hub gasket. Any of the 3 and your parts store should know what you are looking for. Take the new gasket and place it into the hub. Then measure how long of a piece of pipe you need from the inside of the hub up the new drain. Cut the pipe. After you cut to the correct length, take the pipe and scrape the one end on the concrete floor just to put a bit of a bevel on the end of the pipe. By this I mean you want to take the sharp flat edge off the outside of one end of the pipe next you will see why. I usually just take my pvc glue and wipe the inside of the new rubber gasket with glue, and the outside of my piece of pipe on the beveled end, place it in t he top of the new gasket, then take a 2x4 block and PUSH HARD and plop, the pipe will push into the gasket. Once you get the pipe past the first ridge of the gasket, it will push down to the bottom of the hub making a leak-proof connection. Then just glue your new drain onto the top of the pipe and you're all done. Charles.

Charles

You understood exactly my situation, your help is greatly appreciated!
Ron