tsmith6

2014 Silverado 4x4 LT Crew Cab Std Bed; RC Lift: 2.5" Front 2" Rear; Tires: Mickey Thompson Baja ATZ 305/60R18; Wheels: Stock 18x8.5, Factory Offset Undetectable rub while driving in any configuration (towing, reverse...) , but minor paint rubbed off of sway bar.

I had the exact same issue on my 2014. Granted i did not check vacuum but with a little extra rpm's the problem quickly went away. Knowing what I know now I would suggest getting that POS original design off of your truck before it begins to leak oil into the vacuum line and you need to replace $700 of parts instead of the $120 part. If you have concern over which part you have, the parts shop at a GM dealer can verify which part number is on your vehicle the old(12659655) or new(12669488) with your VIN number. The part is definitely different than my original indicating some substantial changes, and will hopefully not have the same problems as the original. I did notice even with the new pump at 700 rpm the truck can lock the brakes from 5 mph as it should, however still at 450-500 rpm I cannot lock up the brakes due to lack of sufficient vacuum, however it does stop significantly better than it did with the old pump. With the old pump the problem was most pronounced for me with my boat on the back barely moving in the driveway (medium grade) and the most recent trip to the boat ramp. On several occasions i noticed it took 2-3 times as far to stop as usual, but only at idle engine speeds. Hopefully GM will see this should be a recalled part so save your receipts and be especially careful backing in boats and stopping on grades with trailers especially if they do not have trailer brakes. Best of luck!