Start saving for a rebuilt.Mine did the same thing I pick it up in a couple hours from the shop.Torque converter going bad screwing up the rest of the transmission.Thought changing the transmission fluid helped because I couldnt get it to do it but yesterday it started shifting hard and that was it.
You have the same problem I did in 1997. I was saving the money to have my tranny rebuilt (1500.00) when I was watching Shadetree Mechanic, now, Two Guys Garage. They endorsed a product called "sudderfix" made by International Lubricants.
Now I have never believed in additives because they are 99.9% junk, but I researched the co. and found they had an excellent rating in the manufacturing community. So I thought it couldn't hurt to spent 10bux for a tube of "shudderfix" since I was going to have the tranny rebuilt anyway. I went to Jiffy Lube and had the fluid changed and had them add the shudderfix and drove on the highway and no shudder, even going up a steep hill. I went home and hooked up my travel trailer and went up the same hill and again no shudder and the tranny shifted much smoother. A couple months later I had Jiffy Lube evacuate my tranny fluid and put in synthetic and another tube of shudderfix and have been driving and towing with it for the past 5 years, all for 10bux. This is my first visit to this form and when I saw your question I registered so I could inform you of this. It really works, how I don't know, but it does. Here's the website address, they are located near you in Washington. www.lubegard.com and click on tranny products and you'll find it. If you use it let me know if it works for you. I have turned on a few people to it here in town and it's worked for them. Cheaper than a rebuild and most important it doesn't harm your tranny
As I said I don't use additives and I do maint on a regular basis and my Bronco has nearly 300k on it. I use only the best.
Good luck, Greg