11bDad

What I'd like to know, is if anyone that is experiencing the vibration has noticed it has lessened, been eliminated, or unchanged with weight in the bed.

Bought a new 2015, Double Cab 4.3 w/Z60 package (2wd & 275/55r20 Continentals). Truck was smooth as silk till 72 to 78 mph & the center console would shake. Not terribly bad, but annoying. Road Force balancing didn't change it, nor did tire rotation. Noticed that as the fuel load would burn off it would be more noticeable. It was more noticeable when the tires were cold, and at times almost gone . Replaced the tires with the same after 55k miles, and no difference. Put (2) 80lb bags of Sacrete back by the tailgate. Things are better but still there. I'm going to add 2 more. I think it's something with the unsprung weight. I've tried the U bolt deal & it did nothing. Hell, 2 bags of concrete mix are cheap, and if it doesn't help I'll use them eventually. What's your folks experience been with the vibration issue when you have 200 to 300 lbs in the bed? Side note: Tranny always ran hot. Had the torque converter and pump changed under warranty at 10K. I added a 20K tranny cooler and changed the part orientation in the tranny thermostat & knocked 30 degrees off my transmission temps.

Glock 26 with a 12 round Pmag or Ruger LCP pocket pistol.

Body of the valve & its parts. Just reverse the order. Put the spring inside the valve on the right, and flip the plunger over. It keeps the orifice between the transmission lines blocked so fluid is constantly flowing through the tranny cooling system. They didn't use these valves prior to 2014. Same transmission, same fluid. My torque converter and pump going out at 10K miles prompted me to change the system to 2013 & earlier temps.

Starting in 2014, GM started installing a Thermal Bypass Valve on the transmissions. It acts like a thermostat, staying closed until the temp reaches approx 190 degrees, then opening to allow fluid to flow through the cooler. Mine did the same thing. During the hot as hell SC summers, mine would run up to 210 degrees before opening (unloaded) and never go below 190. I added a 20K btu Tru Cool tranny cooler and modified the bypass valve. Now I can sit in stop & go traffic at 175 degrees, or run the interstate at 75 mph at 145 degrees. If you guys are interested, I can turn you onto the mod. I doesn't cost anything.

Installed it in Dec, but it didn't do much because of the Thermal Bypass Valve they have used since 2014. Install was fairly easy and I was real pleased with the way it turned out. I modified the valve (easy & free), and it really cooled it down. I can run the interstate in 95 degree SC weather at 145 degrees, or sit in heavy traffic at 175. I used the Tru Cool Mini Max 20k btu cooler. Well made. Torque converter and pump went out at 10k miles, so after dealing with that ordeal I feel better about the tranny running cooler.

The vibration I've been dealing with in the rear of my truck is minor compared to what a lot of you folks have been dealing with, but it's still an aggravation. Truck is vibration free until I reach 72 mph & then there is a slight vibration in the console and seat. It's speed related and did not change when I rotated the tires. Tried the clamps in front of the axle, and that did nothing for the vibration. Moved them 8" behind the axle & there was a very slight improvement. I did however notice that the vibration was less noticeable with a full load of fuel, and the vibration would increase as the fuel was burned. Picked up 2 bags of concrete and put them on either side of the bed by the tailgate. With a full load of fuel, and the concrete, the vibration was almost completely gone. Strange thing is that when I leave for work in the morning, and it's cooler, the vibration is almost unnoticeable, vs when I come home and temps are higher. Next step will be to have the rear tires balanced on the truck & if that doesn't help I'll probably replace the rear shocks with some Bilstein 4600. It's a 2WD, 4.3L, 3.23 rear end with the Z60 package & 20" Continentals. Other than the high speed vibration, the truck rides friggin great.

Other than the trans fluid temp running higher than I'm comfortable with, my 2015 4.3L is doing fine. Little over 3000 miles. I'm going to add a Tru Cool Mini Max trans cooler to it very soon & be done with the high fluid temps.

The AFM in my 2015 Silverado 4.3L (new) would be constantly engaging & disengaging to the point it drove me crazy. At a constant speed it would do this every 10 seconds with a shudder in the steering wheel and gas pedal. AFM disabler arrived Friday & it's like a different truck.

Checked the balance on both rears. Left rear was off 1/4 oz. on the inside, and the RR was out 1/4 on the inside, and 1/2 on the outside. Left rear ran very true, where the RR had a tad of radial run out. Rebalancing took care of 75% of the console and seat shake. Might rotate the RR on the rim 180 degrees & see what that does. I determined the weird, intermittent vibration in the steering wheel and gas pedal is the damn AFM. Driving around in M5 with absolutely no shudder. Running in M6 on the interstate I can still feel it, but it's not as pronounced as it was at lower speeds. Looking at getting a Range AFM disabler.

Picked up a 2015 Silverado LS Dbl Cab 4.3L 2wd two weeks ago. Rides good up to 75 where there is an obvious (not terrible) shake in the rear. Center console shakes, and I can feel it in the seat. I have access to a wheel balancer at work so I'll have the rears checked tomorrow. The one issue I'm concerned about is very slight, rapid vibration that lasts 1 to 2 seconds, which I can feel in the gas pedal & steering wheel. It only occurs at a constant speed between 40 to 50 mph, and happens about every 10 seconds. At the same time the vibration occurs, the tach jumps a 100 or so rpm & settles back down at the same instant the vibration ceases. Doesn't do it when I'm accelerating or de-accelerating. At first I thought it might be the AC clutch engaging, but it does it with the AC off also. Any of you folks run into something like this before? Thanks