swathdiver

Mine has a FlexFuel 5.3 and runs at 43 psi which is commanded state. Key on, the pump goes to 55-60 psi. Supposed to not lose more than 5 psi after key is off.

I've run multiple two way averages in 5 MPH increments to create a log for expected MPGs at a given speed. That being said, mine loses 2 MPG going from 65 to 70 MPH, big brick flying through the air you know. Worked with BlackBear to see if we could tweak the numbers but she just started pinging, was already as good as it was going to get on 93 octane gasoline.

Either the post on the battery is bad (or needs tightening) or the cable(s) is/are corroded and need replacing.

Often a front diff clunking problem is the bushings in the mounts, not the differential itself.

Much obliged Muddkatt! Haven't heard of anyone having problems after having done it but certainly won't recommend this course of action or do it myself anymore.

I've not heard this before, my owner's manual even says to use grease on the slip yoke splines. It's synthetic grease too. Huh.

Well, there's some kind of interference keeping it from working. We see this when programming remotes and TPMS.

Check your u-joints but also pull the driveshafts and grease the splines inside the slip yokes. This is the usual cause of clunks. The transmission is operating normal, keep the fluid clean, clean fluids in everything and she'll treat you good for a long long time. A BlackBear tune will change the way the transmission behaves for the better.

Ok, too far to use mine. Replace the rest of the parts or take it to a dealership with a good reputation and have them put their big smoke machine on it.

Replacing everything, the shotgun approach, costs about $500. You've already done much of it and if the condition of the truck is nice, they are nice to drive and make memories with. Are you in Florida by chance?

Ensure that all parts replaced were GM OE or ACDelco Professional. There is a condition where a leak can exist while the system is under vacuum. This can be tested by a bi-directional scan tool like the Tech-2 which will use the Purge/Seal function to look for a leak. This is a large leak, I suspect the smoke test was not done right/thoroughly. You still have the filler neck, Fuel Tank Pressure Sensor and some more lines that go around the gas tank that could be leaking or their connectors. This stuff is a pain, I've been chasing a small leak for months but am going to buy a smoke machine to finally get after it.

How'd it go after work Pete?

Doubt it unless someone has a bi-directional scan tool like a Snap-On Solus. You don't live on the Treasure Coast of Florida do ya?

Gotta have a Tech-2 to work on these trucks, very hard to diagnose and work on them without one. When I bought my truck, the Tech-2 was budgeted in along with it, wasn't going through that again, being blind and having to rely on the dealerships.

Someone try to steal it? Ok, new battery from store, how old is it? Did you put it on a charger or drive for a couple of hours before this happened? Check your grounds and battery cables for corrosion. Do you know someone with a Tech-2? If this were happening to me I would like to see what's going on with the charging system and if there are any parasitic draws, or shorts or internal trouble codes. https://www.tahoeyukonforum.com/threads/new-battery-and-minor-other-issues-disappear.114687/#post-1379755