O/D light is flashing, rpm are at 5000 and transmission hardly shifts

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I have a 1999 limited edition ford explorer. While driving it started to jolt as I would excelerate and made a noise. Well the problem became worse while driving the rpms would rev but the truck would not move at all. I pulled over started to do a look over checking for smoke or leaks. I saw nothing. I put the truck into 4x4 high And started to move again. Got off the highway and parked the truck waited a Couple of mins took the truck off 4x4 and put it back into drive. I mad it home but the trans was making a noise like a jet taking off. O/D light was flashing and wouldn't shift into gears. My boss had the truck b4 I did and he had the transfer case rebuilt and the decoder motor replaced. So I got a replacement trans from eBay and had my shop do the swap. I went to get the truck today and took it for a test drive the trans shifts but doesn't shift into 3 or 4 or o/d just stays in high revs and can't go faster the 35 40 mph. Anyone have an idea what could cause the problem. And o/d light still flashes.