E4OD Hard shift

[chateau]

1992

Ford

E350 w/ Collins bus body

E40D trans w/ OD



My overdrive light started blinking, and my tranny will shift hard. Intermittently. Limp mode. Code 43(?) Vehicle Speed Sensor. I swapped the sensor but didn't spring for the Ford. No change. Took it to the dealership, they found some rat chewed wires, fixed em, no change. Headed to the junkyard, I'm looking at swapping the speedometer gauge to get a new PSOM, cuz the speedo gets the analog signal from the VSS, but the tranny isn't getting the digital info from the PSOM. I'm thinking PSOM, from what I've read. Maybe the tone ring in the rear differential? Also, I have not checked any of the circuits for resistance, for no other reason then that I'm inexperienced at it. I don't want to get a false positive because I don't know what or where to look. I also have not replaced the tone ring in the rear ABS differential



Meanwhile, my brakes started to lose vacuum when i put it in reverse. I'd lose power brakes. Then it started happening in drive. After a few pumps, I lose vacuum pressure and lose my power brakes. I took it to the dealers, they just want to throw parts at the problem without doing any detective work. They said change the brakemaster cylinder and the booster, if not that, then the vacuum pump. Sounds like a vacuum leak to me, that's why I took it to the pros. I checked the vacuum at the manifold. It's got the proper suction, but the vacuum pump runs non stop. It seem strange that the vacuum pump would operate all the time, unless there is a leak. I changed the booster pump. No difference. It doesn't seem like a master cylinder symptom, so I'm not going to do that until I hear why it would be that.



I'm trying to get her running strong for a Baja trip in a few weeks, and now I'm worried. I need a mentor.