Resetting your idle stop screw is a good idea. It should not be used to cover over an idle problem. It would tend to boost the TV pressure higher than it would have been.

Here is some spec info from an earlier 80s 302 and 351 cars with AOD. Rear axle ratio and tire size will move this around, but these are the general speed ranges for CLOSED THROTTLE downshifts. From 50 MPH or so, take foot off gas, no braking at all:

In Drive OD position, downshifts occur at:
4-3 25 to 40 MPH
3-2 15-20 MPH
2-1 5-10 MPH

In Drive no OD position, downshifts occur at:
3-2 15-20 MPH
2-1 5-10 MPH

One of these downshifts can be hard to perceive, but I don't remember anymore which one it was.

If your idle stop is set correctly,and TV cable is adjusted right, I would expect it to be close to the ranges above. If it is intermittent, by a large amount, I would suspect a sticking valve in the valve body. If you've ever rebuilt an auto trans, and took the valve body all apart for cleaning, there are a lot of very finely machined spools that fit in finely machined bores! Not one nick or grain of grit allowed! And all of the worn-off finely ground friction material and steel microdust from the steels will end up going through the valve body. Finer particles than the filter can catch. Black stuff. In some respects, I'm surprised there aren't more problems with automatics!

 

I am going to fix the idle stop screw today and adjust the TV cable to make sure all is well there. I bought some Lucas Tranny stuff and put about half the bottle in and drove for about 10 miles. I tried to make it downshift hard and it did not, it was the smoothest it has ever been. Thanks for posting that info.

 

I have adjusted the TV cable according to the Haynes manual. I will be driving it later to see if there is any difference.
My tranny does shift just about perfect with your stats you posted. My 4-3 is between 30-40 and 3-2 is is the problem(hard downshift) and 2-1 is almost not even noticable. So 3-2 is the problem, BUT since I put the Lucas Tranny stuff in I have not noticed it downshift hard, but time will tell!.
Thanks,

 

Well most of a bottle of Lucas Tranny stuff and adjusting the TV cable did nothing, the problem is still there. It is worse the faster you stop. If you let the Bronco coast to the stop it's fine but if you are useing the brakes it downshifts hard. It is definelty 3-2 that's the problem. Any more suggestions???

 

Its funny that the brakes make a difference. Like it is unable to do the downshift shift fast enough. But with a long coastdown its OK.

The last external thing that I can think of is to be sure that the throttle linkage, and therefore the TV cable, are going all the way back to the idle position when you take your foot off the gas. So that the TV pressure drops down correctly.

 

Turns out when I adjusted the TV cable I did nothing Cause I did'nt adjust it the right way,(see pic) I popped it off at the RED arrow instead of popping the clip up at the WHITE arrow, so I did not do it the right way. I adjusted it the right way today and it's new position is 1" from where it was before. I drove it alittle and dare I say I think it has fixed the problem, but like I said last time, only time will tell!

 

Wow, 1" is a LOT of adjustment on a TV cable!

 

Yeah, I am starting to loose faith in my Mechanic. Thinking back I am pretty sure this whole shifting problem started back when I had the valve covers replaced but it has gotten worse since then. Also when he did the valve covers he put my plug wires right down beside the engine where they were sure to get as hot as possible. Then to top it all off, when he did brakes on my dad's car he put the break line right on top of the gas line, so over the last year it wore it's way through the gas line and my dad ended up with a leak! I did not have to go anywhere today so I did not get to drive it but I will find out tomorrow if it's truely fixed or not.
Thanks for all the help you guys gave me!

 

OK exactly how did you adjust your cable. I changed my heads a while back and think my cable is affecting my tranny so any help is wanted badly.

 

If you look where the TV cable mounts at the throttle body there is a clip you pop up, once you do that have some one hold back(toward rear of vehical) where the TV cable attaches to the tranny while you push the cable back in and push the clip down.
Thats what I did, now if I did it correctly or not I don't know, it took about 20 miles for it to adjust itself back to normal. I have had no problems since I did this. There are pics at this website you might have to copy and paste that link into the address bar in order to get it to work. Pit in your year model and engine and look around for the tranny section, gives pretty good instructions. Some one on here might be able to explaine how to do it better than I did

 

Hmmm maybe it's just me but can't find picks of it at that site or in my Chilton's manual>

 

Set the parking brake and put the selector lever in Neutral.
Remove the protective cover from the cable.
Make sure that the throttle lever is at the idle stop. If it isn't, check for binding or interference. NEVER ATTEMPT TO ADJUST THE IDLE STOP!
Make sure that the cable is free of sharp bends or is not rubbing on anything throughout its entire length.
Lubricate the TV lever ball stud with chassis lube.
Unlock the locking tab at the throttle body by prying with a small screwdriver.
Install a spring on the TV control lever, to hold it in the rearmost travel position. The spring must exert at least 10 lbs. of force on the lever.
Rotate the transmission outer TV lever 10-30° and slowly allow it to return.
Push down on the locking tab until flush.
Remove the retaining spring from the lever.
The only thing I did not do is rotate the outer TV lever 10-30*, I did everything else.

 

OK, let me get this straight. I disconnect the tv cable end from my throttle body and lift (unlock), the black tab so that the assem. moves freely and can be adjusted. I the attach a spring which exerts 10 lbs. (fish weight scale), on the tv cable end and pull. While holding it at 10 lbs. I then push down the locking tab and then reconnect the cable to the throttle body and I'm done?

I ask because I'm having the same problems with my truck and yes it also goes away when I take it out of OD. I changed the fluid and filter and drained the converter but it did not help. I now also have a whinning noise when I put it in reverse?
Thanks
The newbie!