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Discussion Starter · #1 ·
Very weird issue. The last day or so when I start the truck it's switched itself into 4wdLO at startup. The first time it did it was panic inducing as I started the truck up put it in drive and it lurched forward and made a loud knock from the transfer case. I cursed and freaked about bit. After shifting through the gears with my foot on the brake the SERVICE 4WD light came on which prompted me to look at the selector switches and notice the indicator switch was flashing in 4wdLO. I turned the truck off and then started it again. 4wdLO was illuminated. I pushed 2wd which flashed until the truck was shifted into N at which point it apparently went into 2wd and then drove normally home. From then on the truck has been in 4wdLO every time I start it and I have to shift to N and then select 2wd which will flash until the truck is put into N, not P or D but only N. I'd love thoughts on what sort of evil force has possessed my transfer case/transmission/electronics. I suspect that a weak starter is pull down voltage pretty hard on startup and might be making the truck's systems kind of freak out a bit and send false signals to various systems. The last time I started it it did reset the radio clock the way it does when the battery is disconnected and then reconnected. Thoughts?
 

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Discussion Starter · #2 ·
UPDATE

It's now started in 4wdN with the red light on the last few times and once normally in 2WD. Once I select 2WD with the transmission shifted to N all seems normal.
 

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Was it actually in 4LO or did it just indicate that on the switches? Mine does that sometimes or shows that it's in Neutral, but it's never actually in those gears and drives just fine. Mostly does it when it's cold or moist outside. I'm guessing my encoder is going bad, bad ground, or bad switch. It hasn't given me issues so I haven't dug into it.
 

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Discussion Starter · #4 ·
No it definitely was. The last several times it's been in 4wdN with the red light illuminated. Hasn't started up in 4wdLO since first thing this morning. Once today it started up and indicated in 2wd and went into R and reversed just fine but then when I put it in D the "D" flashed and it wouldn't move. Ground and clattered shifting back into P. Turned it off and back on and it was in 4wdN. Shifted to N hit 2wd and it was good. It's also having something of a "weak" start. Not a long start, it's pretty quick but it just sounds weak. Like the starter is struggling for power. And it may be imagination but it seems the "weaker" the start the more jacked up the tranny and the front diff selector seem to be at startup.
 

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Discussion Starter · #5 · (Edited)
I may have figured it out. The positive terminal on the passenger side battery was pretty gnarled up. Apparently, the mechanic who installed the replacement engine (long story in a previous post) broke off the terminal bolt in the hole. Probably cross threaded too because it’s not seated at the back of threads meaning a stock length bolt won’t snug up the cable to the terminal. They’d shimmed with a nut but the cable was still not making good contact and had obviously arced quite a bit as the red rubber insulation had melted around part of the copper at terminal end of the cable and the battery terminal had some “welding” on it. Stripped back the red rubber cable insulation with a knife and shimmed the bolt with washers and it’s behaved itself perfectly since then. Fingers crossed that the fix is that easy.

UPDATE: Definitely was the bad connection to positive on the passenger side battery that was freaking out the TCM or something. Re-worked the connection to ensure good conductivity and have had no problem since.
 
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