Alright little back story I bought the truck 2 years ago the owner before it “replaced” the engine and the transmission filler neck was off owner swore it had fluid but truck took like 5 seconds to lock in gear towed truck home and a month or so later truck wouldn’t move in any gear so till I realized the tube was off and low fluid transmission had some hard shifts but truck ran like a charm theirs been multiple times recently where the truck randomly seemed to lose all power to wheels “tranny” I’d let it coast and slowly apply gas and it’d start moving again Not much slippage anymore a hard shift here and their but nothing real major whelk today the truck lost all its get up to go on the highway lucky nobody was around but it did this to me 3 or 4 times 2 or 3 times heading to work and once headed home from work I got the truck home and it will barely budge in any gear and just stop the engine will rev while foot is in gas and even redline when the transmission does this but can’t understand all loss of transmission I want to rule out the transmission being shot since it runs pretty good for the most part could their be a chance that high transmission fluid level could go this or possibly the heated O2 sensors I want to figure the transmission out before I start dropping money into getting the truck built nice then getting screwed and needing anew transmission after everything else is done

 

First off, you are the run-on sentence champion of all time!

It's an '02 with how many miles?
The dip stick tube / filler neck was off so was the hole for it plugged or was it left open to the elements (rain + road spray)?
Did you check the ATF's fill level at any point?
Do you have a dipstick?

A common and affordable thing to do would be a pan drop. Have a replacement filter with a gasket ready. MerconV from Walmart is the easiest and cheapest source of fluid.
Remember, the RWD and 4WD have different filters. The 4WD uses a deeper pan and a filter with an extension.

I'm sold on LubeGard (red bottle) and I'd add their 10 oz. bottle with the new fluid because I've experienced improvements with it.
They claim it's a solenoid and valve lubricant, in so may words.

One thing lots of people do to these units is change the valve body. They do go bad and are easily accessible.
I believe valve bodies are available new and rebuilt. If you go rebuilt seek a rebuilder with a good reputation.
However, neither would be inexpensive so I'd go the LubeGard route as an easier "first step".

Go to a junkyard and pick up a dipstick tube and dipstick if you haven't already.

Best 'o Luck