1991 e350 clubwagon 5.8 shifting hesitation

I have this “Adventure Van” . I say adventure because of some of my memorable breakdowns, but that is a separate post. It is doing this thing where around 45-50 it sort of shifts back and forth like it can’t decide if it will go into the overdrive. I’ve tried with the over drive button off and it still does it, the engine light is not on, there are no codes(its old so there are less sensors), the antilock brake indicator is lit. The transmission was rebuilt 5 years ago in Idaho(adventure), with only 5000 more miles added. I replaced TPS, AIC, Termostat 3 years ago, had water pump/timing belt(adventure) done at local place Madisons(PDX), last month did TPS( don’t buy the cheapest parts). It had this revving thing that I thought was related but since the “quality TPS” revving stopped shifting hesitation still happens. A thread about a 1990 Minnie Winnie titled “goes in and out of overdrive and burns up transmission” http://comunity.cartalk.com/tag/e350 . The fix was a short in some wire. Subaru friend Suggest unlooming the harness to the electronic shift control and looking for a short. Another friend suggests maybe shift solinoid, or vacuum leak, but I don’t see and vacuum hoses going into the transmission. Also I am not a mechanic but since covid 19 there is really no need for musicians so I’ve been a “youtube” mechanic. Any suggestions? Ideas? Lighthearted banter?

There’s a component on the side of the transmission called a vacuum modulator with a vacuum hose attached.

Remove the vacuum hose from the modulator, and if transmission fluid leaks out, replace the modulator.


I think my transmission is AOD-E because there is no TV cable and there is electronic control board on the drivers side. Which is weird because wikipedia says 1991 e350s are AOD. I am not seeing any vacuum hose.