I agree with the above, but here's the deal on Trans fluid as I've read: The urban bar-stool myth goes something like, "If you've never changed tranny fluid, and your vehicle is high mile, yer better off leaving it bc new fluid is going to cause caked on sludge inside your tranny to go all over the place and kill it." Tranny books written by people very knowledgeable in the transmission field from the engineering side to the repair side, that I've read indicate that's bunk. A transmission will almost always benefit by a change of new fluid. Transmissions aren't like engines where they get a lot of sludge build-up inside. New fluid w/o suspended particles will have better lubricity and so fourth. And, the myth stems from owners in a situation such as yourself who notice transmission problems change fluid on an aged transmission which 'might' be at the very end of it's life ...sort of like Aaron Rodgers throwing a Hail-Mary pass at the end of a football game. (Yeah, sometimes he scores, but usually he doesn't!!). But we don't know the integrity of your truck's clutch friction material and so fourth. Obviously they're not new, but they might have enough life to go another ...bunch of miles (who knows?).
The only caviet to this is, making sure to use the 'right' fluid ...and you may need to add or adjust anti-shudder agent levels to it afterwards if you notice shuddering. If it does shudder, don't freak out, older tranny's may need a little more anti-shudder additive. And it takes a bit for it to work (not like you add a couple oz and the shudder's instantly gone ..not always the case -- drive it 50 miles). I'd stick to Mopar fluid myself. Small town Chrysler parts departments will often sell tranny fluid out of their 'bulk' barrel for a lot less than the part's jugs. Bring your own clean milk jugs. There are two dealers around here which do that. Don't bother asking at bigger dealers. You'll get laughed at.
A guy could get ALL the old remaining fluid out of the torque converter. The process looks something like this (do at own risk): Add the new fluid after the tranny pan gasket material had cured as per normal. BEFORE starting the vehicle, disconnect 1 radiator tranny line and attach a new clear hose into a white 5gal bucket (don't use a dark colored one). Over-fill the tranny by a couple 3 qts of proper tranny fluid. Have a helper start the truck while the main technician very closely watches the fluid come out. It comes out fast. The moment the observer sees the transmission fluid in the hose run from dark to 'clear' have the partner in the vehicle shut it off instantly. The process takes about 13-16 seconds and it goes by quick. The technician should replace/tighten the tranny lines, top fluid off to the proper level per the service manual. (the tech may need to shut the tk off halfway and add a couple more qts of trans fluid and quickly resume). The torque converter essentially pumps all it's old dirty fluid into the bucket drawing in new fluid from the transmission. It's Kind of like doing an enima. A person doing such a process has gotta use their smarts. That means, such a person should NOT answer gradma's phone call while fluid is pumping out, go to the bathroom, chase a bee, look at birds, change radio station, pull weeds. Don't decide to drive up to the local bar with the line disconnected and fluid spewing out .... then drive home ...with no fluid in the trans (a guy would need more than a few stiff drinks after that!).
Notice I didn't say "You" in the above description. I'm simply describing a particular process. I'm NOT advocating or suggesting you or any other owner/person should perform this.
Anywhoooo, good luck. Let us know if you get your tranny shifting properly again. It's entirely possible the clutches have about a paper-thin amount of friction material left on them and you are about 400 miles from complete failure and no amount of love or care will restore it. But it may also be the case (probably likely) that by doing a little nip & tuck here and there, you can get another 5 years out of it. That's often the case. No way to know really w/o a teardown.
