2004 Explorer: rough gear changes, delayed shifting, stalling...?

I have a 2004 Explorer with 75,000 miles on it under an extended factory warranty. It has never shifted smoothly but I thought it was fairly normal for an SUV. About six months ago, it would occasionally delay before going into gear sporadically, now this happens all the time. One time I put it in reverse and hit the gas and it revved up but didn't move as if it was in neutral. If I hit the gas before waiting several seconds after putting it in gear, it jolts and makes a clanking noise. Every day, getting it into gear takes it about 3 seconds. I have a routine: Warm up Explorer so it won't stall, put in reverse, wait 3 seconds, reverse, put in drive, wait 3 seconds, drive. This is getting very frustrating. If I need to pass someone I have to make sure I have more room than I would ordinarily need as I usually have my foot to the floor for 3 seconds before the Explorer picks up speed. It always stalls if I put the cruise on under 40 mph (my husband's Explorer's cruise works at the speed just fine). I have had it to the shop 3 times and it is there now. The first shop said it was 2 qts low on tranny fluid (there is no dipstick, only mechanics can change fluid), the second shop replaced a solenoid which kept it from stalling as frequently but it still isn't fixed. It is at the shop once again. It doesn't throw up any codes when hooked up to the computer but something is obviously wrong with it and they can't find it. I have googled 2004 Explorer transmissions and apparently this is a common problem, which the Ford mechanic knows about but they still can't/won't fix it! I paid $2,000 for the extended warranty which will expire in a few months. I am frustrated and at my wits end.

I guess my questions is this: Have you had a similar problem with a vehicle and if so, how was it fixed? Are the mechanics trying to screw me over until my warranty expires? Any suggestions? THANKS