Weird problems after having transmssion replaced

I have a 98 explorer. I had the transmission replaced a few weeks ago. the problem now is when put in reverse 4wd lights flash off and on 6 times every 2 minutes. They stop flashing when computer is reset but start again as soon as it put in reverse again. Any one have any idea what is causing this. When put in 4WD can hear transfer case click but indicator light will not come on until computer is reset.