carkhz316

When you replaced the ignition switch, did you make sure you didn't bump that little toothed wheel? If it rotated a little bit before you reassembled everything, your "start" position might only be the "run" position

I guess if it were me, unless it was making noise, I would install an actual oil pressure guage (for testing) and monitor it and see if it corresponds to your symptoms. If it doesn't, then it's that sending unit

No. I don't care what anyone says, all the snake oil in the cans barely do anything. I love Seafoam as much as the next guy, but has anyone have any proof of a poorly running engine that was cured by gunk dumped into the tank? From what I've seen, all accounts are largely anecdotal. There is so much solvent and detergent in modern gasoline that you aren't gaining much. Sure, it never hurts to dump some gunk in the tank, but if you truly have a restricted injector, the best chance you have (short of replacing it) is to utilize a shop-style injection system cleaner or having the the injectors cleaned on the bench via solvent/ ultrasonic cleaning. Just my $.02

Wow. That dealer.......sheesh. Have you checked for codes/ CEL on? Initially, I suspected an ignition switch issue/ voltage drop across the power feed to trans, but the '03+ trucks didn't suffer from the switch issues like 99-02 did, and the 4l60e defaults to 3rd when in limp mode. So, that would imply the shift solenoid A is bad, but if that were the case, you wouldn't/ shouldn't have 1st or 4th when it acts up, but you can get it to kick down too, so this is kinda odd. If you can get a b-directional scan tool plugged in to see what gear is commanded, that would help a lot. Also, try manually shifting from 1, and see how it behaves. If you have all the gears, then it's likely electrical still. I know you mention a dry air filter, but clean the MAF too, because these things will act up and improperly/ TC hunt with a dirty MAF.

Everything is the same between 2500 and 3500 except the springs (as mentioned), and the 3500 get's the 11.5 rearend. Frame is the same, IIRC

Any '03 to 2007/08 (or so) should work.

I know that at least since 2011 (possibly earlier) that if you get a 3500HD with a 6.0 they come with the 11.5, which is similarly around the same time you could get a CCSB SRW 3500 with either diesel or gas well.

When it was acting up, would it go fowards but just not reverse? Just for the heck of it, lift the whole truck off the ground and when in 4WD/ auto, see if the rear wheels are being powered. If not, then you definitely have an issue with the T-case.

Part of the reason for the more difficult shifting is that the Range fork (1 of 2 forks in the T-case) is moving in tandem with the Mode fork, adding to the effort required to move all the parts inside. Also, there is no synchronizer for the shift collar for high/low range like there is for the 4WD output, adding to the effort required. So yes, A gentle roll with the transmission in neutral will make it easiest on you. The pics are from a NP263 I just rebuilt due to being run dry caused by a pump rub failure (check your oil level kids!), but they're virtually identical to yours inside. The first pic is the mode fork (2wd/ 4wd) and the second pic is the range fork (Hi/ Lo). The collar I mentioned is just the left and above in the second pic. This shifts in and out of the planetary gear set to the left in the picture to give you your two speeds.

all 99-06 GMT800 trucks (Sierra, Silvy, Tahoe, burb, etc) are Passlock 2. It's a hall-effect sensor in the lock cylinder that is engaged via the physical cut of the key itself, in addition to allowing you to rotate the cylinder and ignition switch. So, you're correct, there is no electronics/ chip/ RFID in the key, but you'll need to bypass the anti-theft somehow, otherwise when you go to remote start it, it'll "start-then-stall" every time.

I've also bent them, carefully, with no issues and thousands of miles. OP, just wondering......how could you tell they were counterfeit? Just curious. Thanks!

It sure looks like it. What method are you using to bypass the Passlock 2? Immobilizer box or resistor and a relay?

Depending on the style of 2500HD grille guard, it can work. I put one on my 99 2500LD. It was your basic wrap-around chrome brush guard style. The only thing I had to do was make spacers for the vertical bumper bolt attachments for the guard. The rest bolted up just fine. The only other issue was the height difference made it so the lower portion of the wrap-around obscured the turn signals somewhat.

Looks neat and effective, but with even the simplest, smallest mirrors, I'm able to eliminate all blind spots if they're adjusted properly.

There's still a pump, but otherwise you're correct. Good ATF (dex 3 or 6) will work fine. Both can be found at any parts store.