Help me understand my 700r4

[kevinr1970]

This is how I understand a 700r4 to operate.
When travelling at hwy speeds (60-70mph) the tranny is in “fourth” gear with the converter locked. If I apply pressure/give it more gas (to increase speed) or I start going up a grade (increasing the load) the converter will open up/unlock(??) allowing the engine to rev a little higher (stall speed?) providing a little more power. But it is still in “fourth” gear.
If I apply more pressure or go up a steep grade the tranny will actually downshift into “third” gear.

Am I close on this or way off???

The reason I ask is the guy at the shop is telling me that once the tranny is in fourth, the converter should ALWAYS be locked.

On my ’86 long bed I had the following problem:
When at freeway speeds if I encountered the slightest grade the tranny would downshift to third. Sometimes when cruising at 60-70 it would just downshift to “third” for no apparent reason. But usually if I just wanted to increase speed I would give it more gas and it felt sort of like it downshifted, but not really. If I really stepped into it then it would definitely downshift.
It drove fine except for the downshifting to third when it really wasn’t necessary.
The shop fixed this by making the converter “lock-up”.
But it drives like crap. If I want to increase speed, I start to give it gas but it doesn’t seem to do anything. Unless I give it enough pedal to make it downshift to third. If going up a grade I will start losing speed no matter how much more gas I give it, unless I push hard enough to make it downshift.
We have a lot of hills around here so I constantly have to gas it enough to make it downshift. And this is killing my already bad mpg.

So I now have an ’86 short bed. While driving at hwy speeds if I start going up a grade or want to increase my speed I give it more gas. It feels like I am getting more RPM’s (but no tach to verify this). It picks up speed without downshifting. Almost effortlessly? Even while going up a steeper grade, it will accelerate without downshifting. If I really want to get more speed then I put my foot into it and it then downshifts.
This truck has 33’s with a 3.08 gear and it is pretty obvious to me that this is a bad combo (off the line performance is poor). BUT, it drives great! I would think in this situation it would have worse problems but it has no problems at all?

Looking for some help on this and ANY help is appreciated!
I would ask this in the drivetrain section but I have had little luck getting questions answered there.

PS;
Long bed specs:
1/2 ton 4x4
350/700r4
3.73 / 33’s
Manifolds, Y-pipe, cat

Short bed specs:
1/2 ton 4x4
305/700r4
3.08 / 33’s
Headers, H-pipe, two cats