Transmission Slipping or something else?

I'm having a similar issue I think... Have the trans flushed once a year. My tech didn't notice anything out of the ordinary. I'm getting pretty bad what I would call "slippage". In D or 2nd when I let off the gas and slow to 5mph (or so) coast and then apply pressure back to the gas pedal to accelerate the truck revs the RPMs and then catches. Shifting down doesn't help as it seems to happen in 2nd more than D. It's a daily occurrence at this point.

Should I be shopping around for a new transmission or take it to a transmission shop and have it rebuilt? It should also be noted that my '03 DC 4x4 has 342,000 on it and to this point with regular maintenance has had 0 issues.

Could anything else be causing this issue?

 

How does it handle driving at higher speeds and under loads? i.e. down shifting and cruising? I'm always of the thought to check the cheapest things first and work my way to the high dollar issues. I was surprised to find that an ignition coil actually caused some slippage in the transmission. It's all tied together I guess. Coils can check ok cold but when they heat up they tend not to perform as well and get progressively worse. They're simple and inexpensive to change. If you read on my earlier threads you'll see that I purchased one from Rockauto.com for $13.00 and just switched it from cylinder to cylinder until the problem went away. The next step you should take is shift solenoids. Again, cheap and easy. Taco's tranny's are pretty solid mechanically so it could be something very simple. Hope that helps.

 

There is no issue at high speeds just when you let off the gas and coast under 10mph. When under heavy acceleration you can feel some surging like it's pushing, letting off, pushing, letting off...

Just hoping it's something other than a transmission issue.

 

***UPDATE***
So, I figured that the $13 coils might be the cheap way to go and maybe so but I put the three new coils that I ordered along with the one that I had ordered previously in bringing my total new coils to 4. I took it out on the interstate and still lacks power and misses when under a load at 70-80 mph. I said to myself that I should just eliminate the possibility completely that the coils are the issue so I ordered 6 brand new Denso coils. They came Saturday and I popped them in. No change . So to recap what I've done. Truck was running perfectly fine just prior to a rat chewing my knock sensor wire and throwing a code that put the truck in limp mode. I had to drive it that way for about 2 weeks before I could get the new wire and time to replace it. I replaced the wire which required me to remove the air Plenum, fuel injectors, intake manifold and cooling tubes that ran between the heads. When I put it all back together I used RTV on the NEW intake manifold gaskets just for added measure. All codes went away, but the truck missed under loads and also when cranking, sounds like it takes a minute to hit. Previously it would start up with a 1 second turn over of the key. So, Then I replaced all the injectors thinking that I might have a bad one. No change. Then I replaced all the plugs. nothing. Replaced all the coils. nothing. Cranked the engine and saturated the engine bay with propane to see if I had a vacuum leak somewhere. Nothing. Totally out of ideas. It sounds to me like a fuel delivery issue. I did have to unhook the fuel pressure regulator to get the fuel rail out of the way during my repair. When I get a chance I'll have to look and see if the oring might be pinched or not sealing properly. The phenomenon is only noticeable when I first crank the engine, gun it on pulling out or on the interstate at 70-80 mph. When I gun it pulling onto the highway it will start out and respond fine then act like it's starving. If I push the pedal all the way down it'll drop in low and accelerate fine but when it planes out it misses like it's starving for fuel or air. Help!!