@david85 you mention your tranny struggling to produce first gear from a dead stop. My 1990 7.3 e4od is having the same issue, along with revving too high before shifting to 3rd, and often downshifting to 2nd when there's no reason to & then cycling between 2nd & 3rd. Once I hit OD speeds it seems to work fine. I've been manually shifting it (seems to work best starting in 2nd) and that temporarily solves the bigger of the two issues, but I want it fixed.
Took it to a tranny shop and the owner said the transmission seemed relatively good. He replaced a sensor on the trans (I think MLPS?) and recommended I replace the FIPL because he got code 23 (they apparently only work on the trans itself, not related sensors elsewhere). Did that (& tested: currently reads 1.2v at idle/3.9v wot), but no difference. Called shop back and he said could be the solenoid pack but said something to the effect of if I wanted to go to the expense of replacing that, might as well pull the trans, then he could get a better look at if anything needs rebuilding, and either way I might want to consider upgrading with a shift kit once pulled out bc I occasionally haul heavy loads. I'm trying to avoid that expense but will do it if I need to. He seems confident that my "main" issue isn't needing a rebuild.
Other issues that might be related: Speedo needle bounces around. This was minor at first but has been getting worse, sometimes staying at 0 now for a bit, and consistently reading low. I don't care ab an accurate speed gauge, but I'm wondering if whatever is causing this issue is also giving bad info to the trans. Seems very plausible now, but I didn't think this could be it at first, mainly bc these trans issues started before the speedo was noticeably off. Also if this is the obvious problem, I don't understand how the tranny shop missed it too bc I did tell them. But maybe they missed me both saying that & during their test drive somehow. Cruise control also stopped working before the speedo was noticeably off, if that gives any clue. Don't think this matters much, but the orange indicator on the dash of the position of the column shifter doesn't align perfectly when it's fully seated in gear (indicates about half a gear off). Fluid level's good, and had a transmission flush maybe 3k miles ago.
What would you all suggest I check/replace next: VSS? Speedo cable? Or take it to a different tranny shop for a 2nd opinion?