16LT4

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GM somewhat quietly raised the warranty on injectors to 10 years/150k miles. I had one replaced earlier this year; I diagnosed a weeping HPFP via the GM test procedure, replaced it (scraping the intake valves clean while the intake was off), but still couldn't cure the -7% fuel trims and <1% fuel dilution. Knowing the recall, the dealer diagnosed a faulty injector. I had them replace the other 7 while they were in there, because if one failed, the rest aren't far behind, and I refuse to play "whack a mole." I arranged a little bit of price discount, and it only cost an extra $300 for them to do all 8 (with parts/labor warranty) vs. me doing it at my cost. As I'd already done two timing chains in the previous few months, I had them do the weeping front cover seal and oil cooler line at the same time.

Not to mention, illegal.

It’s a 5 year old used truck. What are you expecting?

The stock intake pulls in as cold a bundle of air as can be pulled; aftermarket systems pull warmer air with less filtration. Awesome.

From past used oil analyses, transfer case fluid is due for replacement by 30k miles. Change it.

Mine isn't capless, but I replaced that missing plastic retaining rivet within a week of purchasing my truck; after the first time fueling it up. No need to order GM parts and wait for them to arrive; your FLAPs carries them.

Watch your oil level. If it continues to read higher, you may have a HPFP issue. Check your fuel trims; if they are reading negative, that's further evidence of failed HPFP diaphragm. A DTC won't be stored until about -20%. I'll be replacing mine in the coming weeks; my trims were -5%. Two UOAs showed trace fuel amounts in the oil. When I disconnected the PCV line to the intake duct (making sure to seal all open lines to not create a vacuum leak), I saw my trims rise back to near perfect. That was enough confirmation to order a HPFP and hard line from HPFP to fuel rail distribution block, which is single-use. A CkPS isn't bathed in oil, but because it is reading a tone ring on the crankshaft, gets oil slung on it. New ones (at least on the other brand vehicles I've replaced them on) have o-rings to seal them and prevent oil leaks. Just something to watch in the future.

I'm interested in the slight mpg drop: do you notice this across a tank (on average), around town, on the highway, towing, etc? All else being equal, I'd expect to see a possible drop on the highway, but with a slight gain around town; the affect on the average being of course based on which driving environment the truck sees more. Can you quantify what "slight" is? As much as I would like 3.73s, I know I (most likely) won't be doing it due to my time (too many other projects) and that my truck is what we use predominately to run NY-OBX a few times a year, so I want to eek out whatever mileage I can. In a few years, we'll be looking at today through rose-colored glasses, remembering the "days of cheap fuel, when we didn't really care about mileage." I just like to see the numbers and data, especially on the gear ratio experiment. My '04 FX4 had 3.73s, but also tires that were upsized one sidewall size, and I could feel the difference accelerating from a stop. With only a 4 speed, the upsize was done not only for looks, but also to drop engine RPM on the highway a little, but I could feel it with a trailer.

My 4x4 '16, 5.3 with 6 speed, has G80 rear diff, factory trailer hitch and in-dash trailer brake controller. It also has with 3.42s, so I guess it didn't have the "official" tow package that would have netted 3.73s. Despite being an LT with factory center console and heated front seats, it also came with 17" wheels. I'm not up on the various option packages, but it seems to be some interesting combination of basic and mid-upper level features.

3.73s are what these trucks should have came with across the board anyway; the 5.3 likes/needs to rev, so the 3.73s would help motivating the truck, especially with any weight behind it. Mine has 3.42s. A few trucks ago I had a '14 Ram Laramie with the 5.7, 8 speed ZF, and 3.92s. Between the added power of the engine over the 5.3 (and better torque curve), the perfect shifting of the ZF and the towing gearing, the truck was easily much more comfortable with the same weight trailer behind it, and got the same if not better fuel mileage than my '16 K2 while doing it. Without a trailer, the Ram still achieved 22-23 mpg on the highway, despite more engine and more gears. A 3.73 in the K2 would have a negligible effect, if any, on fuel consumption, and may actually improve around-town mileage due to keeping the engine in its power band. I'd love to see data on that. On a lifted truck with larger tires, definitly need to "gear it;" the larger tires effectively "ungeared it," and probably puts the truck in the 2.xx realm.

Yes. I only post from personal experience. My 6L80 has a bottle of Lubegard and a tube of shudder fixx in it, and drives/shifts as smooth as can be with 107k miles on it. No rapid TC lock/unlock, no Chuggle, no lazy shifts, no shifting confusion. I drove it 190 miles one-way today and trans temps never got higher than 144*F. Fluid is either AC Delco or Valvoline Dex 6 (I forget what I have in it right now). My original 1986 2004-r is also living nicely behind the 350 in my car too, with a bottle of LG. I put in a bottle on every transmission I service, every time.

Lubegard, and in some cased their additional Shudder fix, works wonders on GM transmissions, or any older transmission. I run a bottle in every automatic transmission I own. Misfires are easy enough to see on live data on a scan tool; all engines can misfire to varying degrees without tripping a CEL or registering a DTC, some have a higher threshold than others. This is because ALL engines misfire. Without scantool and diagnostic data, everything will just be a guess.

I've ran my truck with the pill flipped, and now with the 70* updated thermostat. The only reason the pill is still not flipped is to increase the ATF heating rate during NY winters; with the pill flipped during January, I could drive 15 miles and not get ATF out of the 80*F range. On my '16, unfortunately, the ATF heat exchanger is liquid-air, not the liquid-liquid of the last several decades; I wish it was the latter, so it doubled as a heater.

190* is too hot; even 170* is at the farthest realm of proper. Here's my data points: After I upgraded the GM Thermostat two years ago, I towed my VW 200 miles on a car dolly (crossing NYC) in early August, and never saw trans temps higher than 162*F. This past December, I towed my 442 and my '84 GMC 200 miles each way on a 2k lb u-haul trailer on the same cross-NYC route, and never saw temperatures leave the 140s. This route, in addition to crossing NYC onto Long Island, also includes crossing the Taconic Mountains in upstate NY.