davester

With a new TC wiring harness, I would then move to examining the transmission wiring harness where the TC harness plugs into it, that the connector is clean and it's making good connection and the wires are good.

Do you got a non-magnesium rear half? Otherwise, it'll just happen again without installing something like a pressed-metal plate on the oil pump... Anyway, I would start with -seeing if any codes are generated, both with the engine and the tcm (basic code readers won't get tcm codes) -examining the wiring harness in the transfer case area, that it looks good and didn't get pulled on, and that the connectors are nice and clean

Is the TC harness still connected to the transmission harness (at least, that's how it's done on my truck, it's effectively just a short extension for the transmission wiring harness going to the 2wd sensor)? Maybe also pull the speed sensor and see if the tone ring is centered in the hole. I know it's possible to install the ring backwards, which may offset it from the sensor.

If the OD clutch plates are gone, then the transmission needs to be worked on (as the OD clutch is in the transmission). I would first try to figure out why the torque converter seems to be able to lock up in 3rd, but not in OD. Is in the OD clutches slipping when the extra power going into the transmission as the converter locks up, or is the OD clutch not slipping, but the converter no longer can lock up with the extra torque going through it in OD, or is it some internal transmission problem, where when the OD clutch is engaged, it can't get enable the converter to lock.

IIRC, when I changed out my sway bar links, one side was no problem (duh, the sway could pretty freely rotate because both ends were disconnected), but the other end was too far apart, so I had to jack up the opposite wheel a bit to get it started. So, I would suggest you jack up the wheel for the side you are working on to get more space between the sway bar and the control bar (or jack up the frame on the other side of the truck so the opposite wheel effectively drops relative to the frame).

Big O, what are the codes you were getting? It certainly could be the OD clutches have finally be used up, after 270k... I would lean more towards that than the converter, given that the converter seems to be locking up in 3rd. But I would suggest using a tech ii or autogenuity or something that can read the transmission computer and tell you when the TC is locked, what gear it's in, and transmission input and output speeds, to more precisely know whats happening in the transmission.

If you still have the cat's installed, they are the main source of backpressure, not the exhaust/muffler system after it. You might consider replacing the in-line fuel filter (inside the frame rail, under where the driver sits). I took out my injectors and soaked them in Seafoam directly, as well as blew out dirt caught on the inlet screens. I don't know how well it worked, as immediately after this, I accidentally used a bunch of REALLY dirty fuel, and promptly loaded them up with crap again, and bought new injectors off ebay. I believe GM has a setup to inject a cleaning fluid through the pressure sensing port on the fuel rail, but I don't know how effective it might be.

I don't know how long these engines last, but they are pretty good. Mine has about 160k miles on it, and the oil level only goes down 1 notch on the dipstick between oil changes (about 5000 miles). For me, the main problem is figuring out why the engine doesn't run efficiently. Over time, various sensors/whatever slowly go out of whack, and it can be a challenge to figure out which one/s aren't up to snuff.

the transfer case is notorious for having a "pump rub" problem, where the internal pump slowly wears a hole in the case, all the fluid comes out while you are driving, then the TC turns into a growly bucket of parts that needs fixing. all the various oil lines leak over time (engine oil, transmission oil, power steering) depending on where you are, brake lines have a rust problem (easy spot to check is where the 4 lines meet in the driver's side wheel well, and go along the frame rail to the ABS controller, they tend to be the worst there because they get splashed from the wheel, but the rear line also gets bad where it's mounted along the frame rail above the fuel tank, but it's difficult to see there).

You have checked ALL the fuses? I've found that non-obvious/related fuses can cause the BCM to not work right (as in, not power various items it drives).

I would suggest flushing both, as brake fluid goes bad over time, and I know flushing the PS fluid with new stuff helped make my brake pedal a little firmer. I believe the temp is sent digitally to the IP, so I would think your IP has failed, either the computer on it, or perhaps one of the traces to the stepper motor is broken.

is the power steering fluid full when did you last flush the power steering fluid is the brake fluid full when did you last flush the brake fluid how much of the pads are left at each corner As for the temp problem, have you considered checking the sender and/or the wiring for it?

1. I don't believe your truck has rear wheel speed sensors, but rather relies on the VSS in either the transmission or the transfer case. 2. Post the actual code, as there is no real way for the truck to notice whether or not the calipers are releasing, short of the wheel locking up. 3. You replaced the broken wheel speed sensor?

go to a parts store with a code reader that can read ABS codes, and get them to scan for codes.

don't forget to change the transmission and transfer case fluids if they haven't been done in awhile.