2000 130k (new to me)

-truck majorly lacks power and rpms but only after operating +2 hrs
-It threw a P1875 the other day after 6-8 hours operating (cleared two days ago, yet to repeat)
-tcase was filled with wrong fluid (drained the tcase oil today but it was pretty nasty, plan is to run it another day and drain/refill again) I have no idea how many miles went on like this
-between 10-30 mph it's at its worst (no power and rpm drops, plus it feels like the front axle tries to engage on dry pavement even in 2wd mode)

 

I would start by checking fuel pressure and doing a leak down test. Next clean the maf sensor then look into doing a full tune up, depending on how the pressure and leak down test go.

 

96+ Fuel System Diagnosis - Blazer Forum - Chevy Blazer Forums

this should show you how to test the fuel system

 

I cleaned the MAF sensor, did plugs/wires, rotor and distrib cap, but it didn't fix the problem.

SO I read a post on here about the TCCM convincing the truck that it is in 4wd lo. I took the unit out and the problem seems to be gone. Like I said it did throw a p1875. I found three leads on the orange connector to be corroded.

I haven't put the unit back in yet because there is rust on the mounting bracket. It seems lots of air and moisture are getting into the truck somewhere near that passenger kick panel, thus f-ing up the TCCM, but I can't figure out from where. Door seems to be sealing good...any ideas?