I have a 99 f250 superduty with a 4r100 2x4 transmission. the t/c is not wanting to stay locked up its staying unlocked, the o/d light keep blinking, and now it started idleing high when put in park. I have just changed fluid and filter in the transmission. nothing in the pan fluid wasn't burnt or anything. Also just put a bigger trans cooler on it. Any Ideas on what it could be. I was thinking the oss sensor. And I was wondering if the oss sensor is the same for a 2x4 and a 4x4 4r100.

 

If the OD light is blinking it most likely has one or more codes (DTCs) stored. You need the codes read by a shop. The DTCs will tell you where to begin.

 

I have a lot of ideas what it could be. I can list everything that could cause this, and you could go buy all those parts and see if any of them fixed it.

Or you could get the codes read and then we would KNOW what's wrong. Your choice.