97 4-speed questions

Hi you'uns. New to the board. Got a potentially major problem, hoping to find some help here.

P0700: MIL
P0784:4-5 shift malfunction
P0736:Reverse incorrect gear ratio

When cold; will go into reverse and then forward until you take foot off gas then sits still until fluid warms up(has happened in the middle of an intersection-very scary.) Stepping on gas had no effect. Shift position lights go haywire during this warming up period. Once fluid heats up, will operate normally. Wife had this experience this morning, luckily, it happened only 500 feet from house and before she could get into traffic. She backed it up into driveway and walked to work. I let it warm up for a while, then drove it to O'Reilly's and used their code reader to get these codes. Operated normally during entire trip. Guy behind the counter at OReilly's asked a guy back in the office about these codes. Guy back in the office says I'll have to replace a module that is inside the tranny. Please tell me he's wrong. If he's not wrong, please tell me removing and replacing the tranny is something I can do myself. First time this happened to me, I just added fluid and it seemed to be fine. Problem persists and worsens.

What engine, mileage and when was the last time the tranny filter and fluid were changed??? ATTF+4 only.

Yep, you guessed it. Fluid had not been changed in quite awhile. Once I did that, all symptom magically disappeared. Clogged filter arrrrgh.

clogged filter can be a problem. My cooler failed and filled my transmission with water. I flushed the transmission with about 20 quarts and changed the radiator. Drove about 150 miles, pulled in my driveway to put the seats back in the van, put it in gear and nothing. I finally floored it a number ot fimes and it moved a bit into the garage. I got it out of the garage pulled the pan and the new filter was totally clogged up. changed it again and same problem. I pulled the transmission and did a rebuild and it is almost spotless inside. Guess all the transmission fluid really cleaned out the sludge. Clutches and bands were all ok, but replaced them and seals anyway. So, if you let your transmission go too long as I did you may need to do two or three back to back filter changes to get all the sludge out. It could have been coming from the torque converter also, but have a new one of those so evrything should be fine.

Yep, you guessed it. Fluid had not been changed in quite awhile. Once I did that, all symptom magically disappeared. Clogged filter arrrrgh.

You deserve a medal for admitting your mistake. This and other forums are filled with posts about tranny problems without a fix posted. Any bets on how many of them ended up fixing it just as you did? Your honesty is refreshing.

I change the tranny fluid annually using a pump no matter the mileage. I drop the pan and change the filter every 3 years. Not a hickup in 197K miles.