4WD and Shifter Mystery


SDD Junior Member
Jan 28, 2017
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Washington State
Hey all. Let me start by saying I am mildly mechanical and willing to check and repair basic items, but I don't have a garage and my regular diesel mechanic is booked 2 months out. So coming here for ideas. Apologies in advance for the length of this description. It's really weird to me. 2002 F350 7.3L 4WD SRW Crew Cab:
Within the last week or so, within a few minutes of a cold start (typically mornings at temps from 50-70F), the Check Engine light comes on after driving at low power for 100 yards, but extinguishes after just a minute or two at non-highway speeds. I have a code reader and it does not turn up any fault codes when the lamp is illuminated. No driving performance issues are immediately apparent. Oil and transmission levels are AOK. Batteries charged.
The next anomaly began 2 days ago where, after a 30 minutes highway drive, after exiting, I noticed in a sharp turn that the truck seemed to be in 4WD High. No lights on the dash to indicate such. But in reverse, it also feels like it's in 4WD as well. Suspecting a vacuum issue, I checked the AC mixer/diverter and it works fine. Hubs are unlocked, and I even replaced the PVH solenoid as a quick check. No improvement. When pulling the PVH, I could hear the vacuum system discharging, so it seems there are no leaks. I checked the ESOTF fuse in the panel and it is good. I DID NOT check voltage or impedance on the PVH leads. So this could be an electrical issue.
Lastly, as of yesterday, after starting and attempting to put the truck in DRIVE, it doesn't engage. No REVERSE either. When trying to throw it back in PARK, it grinds awfully and just won't go. Turning the truck off. And then turning to ACCESSORY, and cycling the shifter, back to park, then startup, ALL COMES BACK TO NORMAL.
Mind you, this is a one year old transmission with less than 10k miles on it and no signs of performance issues.
Back in January, I did have an issue with the 4WD lockout being stuck in 4WD Low and it had to be replaced. None of these other issues were present at that time. Could this have failed again - or differently.
Quite a mystery to me. Especially with the various anomalies occurring within a few days of each other. I appreciate whatever guidance anyone can offer.
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