Ok... NOW WHAT?
01 Durango 360 4wd 311k+, trans rebuilt at 258k, has worked great all along
trans was rebuilt when it was only because I didn't know it's history prior to my buying it and I was putting an engine in anyway so it was one of those "might as wells".... not because of any specific problem at the time. ive owned since 214k.
When it was rebuilt (by me with the assistance of a many years Chrysler dealership trans guy guiding me) it got a fresh converter, and a transgo TFOD jr shift kit and new solenoids. Fluid is currently clean and pink as new, and full. Fluid and filter was changed 10k ago.

It worked just fine up until today. Before today it was last driven last week Friday, because Saturday I had to pull the dash out for a new evaporator.it took me a few days chasing parts, letting JB weld dry in the heater box, etc...
I've started it up and let it run a while yesterday in the driveway while charging the AC.
Yesterday when I first reconnected the battery it seemed to want to lunge forward in park slightly when started, which it has never done before. I took it for a ride a while ago (had to backtrack a bit due to a couple of lights on the dash that weren't before-- a couple of wiring plugs that I thought were secure but really weren't, was all that caused those.)
Sorry for the long back story but hopefully it will help.

Took it down the road a little bit ago and was fine to begin with, stopped and started a few times, and no issues.
I stopped for gas about halfway through the test drive, (about 15 miles total there) and when I started to pull out of the gas station I got a helluva shudder out of the trans from starting out to about 30-ish. Weird, never had this one act like that.
Went thru all the gears and lock Up, no problem noted in higher gears. Stopped for light, shuddered, and seemed to slip a bit but if I did feather it til again around 25-30, then fine once it finished it's fit.
Above those speeds it acts normal
I took a little detour (just a handful of blocks) where I could stop n start a few times and every time except maybe once, it shuddered on takeoff.
IT NEVER HAS DONE THIS, before I pulled the dash out and had the battery disconnected for a few days in the process. I definitely see no relationship between pulling the dash and sudden trans issues immediately upon finishing that up.
I used to know a little about these transmissions back in the day when they were "current production" but I have forgotten a few things since.

One thing that was really weird was that when I reconnected the battery and started it up to charge the AC, the speedo pegged itself at 120 and it did have a code for no speed sensor signal. I unhooked the battery again today to clean the terminals, (especially the "+") and when I reconnected it, the speedo appeared more as it always has, At "0" and has worked fine all the while I drove it.
Immediately upon seeing the speedo needle at the wrong end of the scale I scanned it and had a code for no speed signal seen, cleared it and it hasn't come back. I had other unrelated codes (like air bag, "service 4wd" light, only because I had it unhooked) none of those codes I had have returned.

Well, you went and done it now! You gave some parts some love and attention, and now some other parts are jealous and want some attention too.

If today was the 1st time event, and that was after the battery has been disconnected for a few days, I wouldn't put much stock into todays events. I'd write it off as the computer reminding itself how you drive. If it happens a few days in a row, then I would look into it. A starting point may be the speed sensor, since it has set a code once. The computer uses its output to determine that the vehicle is moving, if its not getting that signal, it doesn't know the the vehicle is moving and could be causing the shutter at low speeds, but as the speed increases, the sensor starts working again. If it does it a few times, it should set a code.

I did find a pretty good 46RE transmission shop manual on line that helped me a lot with my trans deal. It is a free downloadable manual. That source is www.ProCarManuals.com

Ok... I talked to my Mopar dealership trans buddy, and he came up with a weird as hell possibility.
He told me of a dodge van he had in his bay and was doing similar weird stuff.
I just drive it with my snap on Solus scanner connected and watched what parameters I could as I drove among the cornfields.
I know that desired governor pressure roughly follows speed in MPH.
Actual governor pressure was pretty close. Desired though flickered from close to actual, sometimes it would want "desired" gov pressure to be close to actual, other times it would "desire" 2x speed. I tried to hold a steady speed while handling the scanner of around 60-63ish. Actual governor pressure was pretty close, there were times it would show "desired" at 126psi. Other times it would "desire around 47psi. But all the while, actual followed speed. Like it should.
His suggestion was to add a redundant ground from the trans case to the battery and see if that cures it.
If so the problem is something to do with the clock spring, as I guess the trans solenoids ground thru there.
He had called the dealer accessible hotline on this van and they said to do the redundant ground as a test.
Weird but I did have the clock spring disconnected.
In fact I had a code for it and an "air bag" light right off the bat when I first started it up on reconnecting the battery. Come to find out that I didn't have it plugged in all the way which ended up an easy fix, once I got it snapped in the air bag light stayed off and code stayed gone.

I haven't tried the redundant ground idea yet but gotta ask
I've got an extra ground already from the back of the head to the firewall from when I swapped engines some years ago.
The engine is bolted to the trans. I didn't mess with anything underneath when I had the dash out. So I don't see adding yet another ground really doing anything for me.
Would I have to go from the trans to the battery? Block to battery? Ground stud on firewall where those head straps attach to the battery? All of the above? Like i say I ain't seeing it.

Went from a bad evaporator and perfectly working trans to new evaporator, new heater core, new blower motor, new blower motor resistor, and all new actuators on the HVAC box plus a draw down and recharge of the AC, to a trans that's FUBAR that worked perfectly before I had the dash apart.

Grounds have been a possible cause of weird things since they started using a chassis ground. You can just run a jumper wire as a test.

Real world examples that happened to me:

Mid-70's Dodge pickup when I was in England in the USAF around 1986. driver came in and said whenever they turned on the turn signal, the wipers would move in time with the signals flashing. They thought the truck was possessed. Cleaned the ground wire on the battery and block, added #8 wires from block to body and body to battery. problem solved.

Rusted out POS Chevy Monza my BIL had, kept breaking clutch cables. He asked me to take a look at it; popped the hood: brand new ground cable bolted to the frame, not the block. Clutch had to be depressed to crank it, power flowed through the starter but the only path back to the battery was through the clutch cable attached to the clutch fork and the pedal. The cable kept breaking at the crimped on slug that hooked onto the fork after it got heated up a number of times.

Few years ago I bought a Dorman clock spring that wouldn't plug in smoothly. I used a bit of force to get it seated. Starting the truck cleared the airbag light, but the turn signals (or hazards) wouldn't blink. Bought a different brand and the connector looked like OEM, fit perfect and solved everything.

I would start by checking the firewall connection of that firewall extra ground you added for corrosion.

I've been playing with Mopars for many years. 20 years ago I started adding a secondary ground loop on nearly every electrical component under the hood. I have not had an electrical issue with my stuff since. That ground loop is a 10 gauge wire connected to a bunch of 1/4" electrical eyelets.

I drill a 1/4" hole through the firewall at an easy to access location, a 1/4" hole in the dash frame at an accessible location, a 1/4" hole in an accessible location near both headlights, and between the tail lights. after the holes are drilled, I remove any paint around the hole to expose bare shinny steel on both sides of the metal. I put a 1/4" x 1" long bolt through the hole with a flat washer on each side of the metal with the hole, then I will put on a 1/4" nut and tighten the bolt tight. I have created very good ground sources within reach of everything that may need a good ground. !0 years down the road, if its looking funky I simply remove the bolt, reclean the metal, and install a new bolt.
On the ground bolt I will connect the 10 gauge wire eyelets (one for each item in the area that needs a good ground), you can usually put 4 or 5 eyelets on each bolt, then I add just a 1/4" nut to tighten the eyelets between the two nuts. If some of those ground bolts are not far apart, and don't have too many eyelets already attached, I will interconnect them together and have one eyelet grounded to the battery.

I ground my headlights, front turn signal lights, tail/brake lights, any thing needed grounding under the dash, or anything bolted to the firewall on these ground bolts. I also run a ground wire under at least one mounting hole of every electric powered thing bolted to the fenders, or firewall to each other and to at least one of the grounding bolts.

I learned a long time ago that a self tapping screw into sheet metal is a poor ground after a couple years. If something electrical is mounted to sheet metal with self tapping screws (or bolts) it gets connected to the ground loop with an eyelet under one of those mounting screws. Mopar uses a lot of self tapping mounting screws as grounds, every one of them is suspect in a few years if you live someplace with moisture in the air.

Yes, its probably over kill, but it eliminates many ground issues. Those ground bolts sure provide a good ground to connect test equipment to as well.

You have to drop the steering column to get the dash out, Trans lever is part of the column. So it's possible the linkage is off. Lunging forward in park? I would check the linkage, It should not not move in park.

I did disconnect the shift cable, but didn't change any settings up top by doing so ... But how it would want to lunge forward being there's "reverse"and a "neutral" between "park"and "drive" further confounds things.
I've had vehicles with slightly off shift linkage and they tend to go backwards until the linkage is readjusted bot forward. But it's something else to check on

Well it's out, but not apart yet. I have another from under the bench to swap in, I'm gonna go thru this one when I get the chance, I put a drain plug in the pan quite a while back...and I pulled it the fluid looked worse than on the stick and a little bit to "glittery" for me. The biggest problem I'm having is finding someone with the right front pump seal in stock, and I'm not a fan of unknown quality "house brand" I'm off a few days for the 4th, and I'm hearing the 5th before I can get a seal. I got the Taiwan one from o'wrongleys, (house brand) I hope that doesn't bite me.

Ok update time. STILL having an issue.
Replacement trans is in. Son of a b*tch, $132 for a case of ATF+4? [censored]??? That's obscene

I BETTER not have to pull the pan for at least 25-30k miles.... That's more than I paid for this replacement trans in a u pull 3-4 years ago.
Anyway the shudder and slip is gone. Much better.
So there is some mechanical problem that's "up" within the original transmission.
But I still have the same problem with governor pressure.
Desired goes to 126.8 as soon as I got 34 MPH and stays there. Unless/until I release the gas pedal and coast. Then it reverts to what I would expect it to, if a little below. I just TOUCHED the gas and right back to 126.8. no matter what my actual speed is. Voltage jumps from 1.95v to 3.xx volts, at that point. Skips over the 2.xx to 3.1x volts range. Yet when I coast it will settle in that range just fine as long as I continue to coast and not touch the gas.

The difference now with this trans is that actual governor pressure doesn't act like it "knows better"
Like with the other trans, "actual" would remain about where id expect it to be.
With this trans it tries to catch up with "desired". It likes to run 70-80s and occasionally touch 90psi as long as I'm on the gas. When I hit 60-65 mph and level off, actual psi is around 10-15 psi higher than the mph I happen to be going. But while accelerating it can go 20-30psi higher than MPH.

HELP selling/trading in is out of the question. I have to get to the bottom of this issue.

I have also monitored the tps , all parameters from voltage to % open, and there are no glitches there.
I have added 3 redundant grounds before I swapped the trans with no satisfaction from it.

C'mon guys...I'm reaching... Who are our moparts electrical wizards here?
I'm 98% sure I'm chasing an electrical issue now, not a trans mechanical issue anymore.

Online service manual that covers the line pressures, what they mean, and the probable causes.
The manuals are free, but are only on line. Printing pages was not very helpful, so be prepared to take notes. I suggest you draw diagrams of the pin outs that concern your transmission. The manual starts out explaining its function, then it gives all the electrical connections and their pinouts (for all these trans options), then it goes into the service procedures. It often refers back to the pin out figures, but you have to roll the pages of the manual all the way back to view the figure, then roll the pages all the way to the test procedures.

www.procarmanuals.com

Automatic transmissions

Dodge

46re-47RE-48RE- ATSG is the trans line you are looking for.(don't confuse it for the GM version)
.
When the picture shows up, you enlarge it with the X in the bottom right corner of the header bar under the pic.

It covers all of these transmissions, you do have to sort the things that apply to the model and the year of trans you have.

Thanks for trying to help but I keep getting a circle jerk there, and can't get it to open.

How are getting that pressure reading from the governor port? Governor pressure should be about 1 psi per mile and hour.
Look over this.

Yes I know what gov pressure "should" be.
That's why I'm questioning things. .
I don't have a test gauge like that any more, so that's not where my readings are coming from.
I'm getting those from the screen of a snap on Solus scanner, the 126.8 is coming back as the "desired" governor pressure on the scanner any time I cross 34 MPH and am touching the gas. No matter how lightly. If I let off and coast the "desired" goes back where id expect, if a little bit low, and "actual" follows suit.
From a standing start til 34 MPH it is acting as if expect.

I still think there is a wiring issue within the dash causing this from when I replaced the evaporator and heater core the week before. Because the problem that happened within the trans is mechanical (something ate itself) and with 311 k miles im chalking that part of the problem up to coincidence.
But when the original trans started acting up on me I plugged in the scanner and the gov pressure was acting exactly the same.

The original reason I swapped the trans ( shuddering and slippage in 1st and 2nd gears) is fine now with the replacement trans. But the governor pressures as read thru the scanner is acting exactly the between the 2 transmissions Ive had in there.
So that pretty much rules out the tranny itself as the reason for the screwy governor pressure readings.

Lots of good info here regarding grounds and consistent electrical connections on "non factory" installations like lots of us make when building our custom vehicles.

Gets me thinking about the corroded, failed, braided strap that runs from the firewall to the engine on my 2001 Dakota. I never replaced that strap since everything at the time worked ok. But these days the left turn blinkers flash faster than the right, and I get some random/intermittent warning dings in the cab although everything is normal running wise.

Huh I had put up another reply, I don't see it.
Not gonna repeat that right now, but will say I haven't been able to get back to it for a few days, hopefully this weekend I'll get back to it