I have a jr xr2 and I was curious to know which rx where compatible with it? I got a xr2 for free but it had no rx so I need to find out what works with it and where to get them.

You say old? Im guessing its still the old am or fm radio. Just find an am or fm reciever and use matching crystals. I mixed and matched recivers an transmitters all the time.

Yes it says 75mhz on it. I don't know if it's am or fm though how does one tell that ?

It should be AM.

yes its am

Yes as you said it AM.

Just a note, I did have some glitching issues when using Futaba receivers with this radio, but any off brand, JR, or Novak seemed to work fine. Even used Traxxas AM receivers in the past, without issue.

Really? Ima have to give this a try

It worked for me.
Good Luck....

Does it matter if there 27 or 75 mhz?

If the radio is 75mhz the rx must be 75mhz and vice versa

Thanks now to find some 75 mhz rx