So on top of the issue with my U-joints going out, I am starting to have this issue and I can’t figure out if it’s my torque converter going out or my transmission. A little side note, a couple weeks ago a belt shredded off and put a huge gash in my transmission cooler hose from the tranny to the rad. Got it fixed that day after a few hours of dealing with headache, since I filled the tranny with the proper amount of atf, it shifts smoothly now and holds its gears… until today. I was driving out of town and it still shifts smoothly from first to second, but when it hits 35mph to 40mph it can’t decide whether it wants to be in second or third and when I give it a little more pedal sometimes it keeps it from doing that, also sometimes it will do it, and sometimes it won’t. Once I hit 45mph no issue, drives just fine. Can anyone think of the cause for this issue?
1986 F-250 Diesel
7.3 IDI (It was a conversion due to the 6.9 being bad in it originally)
2WD
C6 Auto
4.10 Rear