asilverblazer

gmupfitter.org More measurements than you could shake a stick at.

I would normally say the fuel pump is bad, base don your pressure dropping when you shut it off, but sounds like it could be the regulator letting off too much pressure the pump can't build up enough, causing drivability problems. I can't recall regulator test procedures from memory though.

Try a year older or newer to see if it pulls up a different part number that matches the shaft off the truck. The noise I bet is from the bearing, so you might be able to put it back together although you've already got it apart...

Only would be problem if it was tied to the trailer brake output in the harness - I doubt it. I adjust the brake shoes on my trailers to a moderate drag. (Light drag being turns with no or little restriction and hearing a slight noise when spinning, heavy being hard to spin by hand. Moderate can be spun but definite contact and noise. I like it this way to make sure my shoes get a good bedding to the drum and strong sense of engagement when in use.) As long as you aren't getting any errors, I'd start with adjusting the shoes.

Sounds like you actually had a problem with the AFM lifter not collapsing properly and still engaging the pushrods - opening and closing the valves still. Now the problem is masked.

For sure, cables can rot out inside the insulation and you can't see it.

I'm running out of ideas... when it is acting up pull fuses to see if what circuit is causing it or are immune to it. Make a detailed note of what circuits are dropping voltage and are not. Track all the good circuits and bad circuits on a wiring diagram to see what are grouped together or other common points. What happens if you shut the truck off and restart it? You checked all the cab grounds, what about cab to chassis?

Can you have someone hold the RPMs where it is making the noise in Park and listen with a mechanics stethoscope? Is it the sound causing something to vibrate - the catalytic converter is in that area - the media inside could be broken and rattling. Heatshield... Happening in park and neutral leads me away from transmission.

I used to have a bunch of subscriptions - but let them all lapse when they went up to $50 per car.

So I must not have read the original post well enough... Sounds like you've isolated it to the cab and checked grounds. I would start trying to isolate circuits if possible. Also check the wire harness where it goes into the cab at the firewall next to the brake booster. Wouldn't hurt to check the BCM either. Weather conditions make it worse? Water could be leaking into something...

...keep reading...

When you notice the vibration, put the truck in neutral let the revs go down or/rev the engine up - does the vibration change? Isolates the vibration to either engine or drivetrain. Engine loaded vibrations could be misfires. (Check engine light on?) Try different combinations of gear selection, speed, rpm - a speed only related vibration is not caused by engine or transmission. Speed related vibrations check tire balance, drive shaft balanced and true, worn u-joints. When you notice the vibration lightly rest your foot on the brake (only enough to turn the brake lights on) does the vibration go away? If so check the torque converter clutch. Could also be something as simple as some mud build up on the tire or rim.

Warning lights are coming on because of the low voltage. Sounds like your alternator and/or battery is going bad. The alternator should keep voltage above 12 volts while running, the battery stores the voltage for when the alternator is producing power. Problem 1 is the alternator isn't keeping voltage up while running. Problem 2 is the battery isn't keeping the 12 volts up, while the alternator is out - unless you are running it long enough that any available voltage in the battery gets depleted.

There is another thread on here about this... last time I checked no solution from GM yet. There is a code, I suspect the dealer will discover it while they are checking which will point them to the bulletin about the problem. Search it out, the thread is something about trailer brakes and buggy rear camera.

Wonder if Denali tailights would plug in... they are separated.

Dimmer switch turned up?

Not sure if the ECM does that... I suppose it COULD, if the ECM has a misfire on a cylinder, it could shut off the injector to protect the catalytic converter. The easiest test to me is to confirm that the injector is behaving like the rest and if not why.

Sounds like it would be easier to run a dedicated circuit from the auxillary battery to the trailer plugs to me. Check out gm-upfitter to find a wiring diagram. Also, look at the underside of the underhood fuse box. That circuit is fused there, you can trace it out of the underhood fuse box and intercept it (or - remove it from the underhood fuse box and re-route it) to the auxillary battery.

Compare that injector pulse to other injectors on the same bank (maybe you are only seeing it pulse heavy to start - then the idle pulse is too short/little to pick up). The ECU wouldn't normally shut down that one injector.

I've had the Bridgestone tires and prefer the BFG. The BFG tires wore better for me.

Sounds like you are referring to trailer wiring - If memory serves, a 7 pin harness is taped above the spare tire for trailering (if it isn't already terminated in the plug on the bumper). A separate 4 pin harness that plugs into the BCM and is connected to an aftermarket brake controller is done under the dash. Lastly, a wire (red with black tracer taped along the main harness next to the fuse box) must be connected to the extra terminal on the side and corresponding fuse installed (30 amp maxi).

Basically agree with the above. Also, the quantity and weight of animals being carried can vary, so to keep the tongue weight from becoming too little the axles are further back.

In a 2wd truck... required too add some weight in the rear for traction to take off from stops, taking off uphill will be challenging. Snow = medium Ice = hard Traveling on snow is possible. Traveling on ice is not practical, a safe speed is generally so slow its better to just wait for it clear, likely less than 24hrs in the south.

Multiple tire failures... Pick up a nail while driving, immediately pull over (obviously), tire destroyed internally and cannot be repaired. All my other tires can at least make it to the shoulder before becoming unusable. This happened a few times on Michelin tires. Not particularly Michelin's fault but I only had this issue with that brand tires. Nail in the coffin was driving down the road and had a blow out, no road debris and critically the tire was at the proper pressure (I monitor tire pressure manually and via the tire pressure monitors), immediately pull over and the tire is destroyed. Michelin's response was it was a result of driving with no air which was blatantly false. They wouldn't warranty the tire, so I won't use them. I've had excellent results with BFG tires (longevity, traction, durability, NVH...) so that's what I use. Every time I use something else like Pirelli, Bridgestone, Goodyear, Continental - I regret it. Tires are too expensive to 'try' something else, I'll stick with what works for me.