abominable z71

I haven't been on this site for quite some time so I apologize for lengthy post, I was hoping that this thread was pretty much dead and someone had found the fix for the dreaded Chevy Shake. I'm sad to see that's not the case. I gave up after countless hours and thousands of dollars, I replaced damn near everything underneath the truck including the drive shaft even though I knew it wasn't the issue I was desperate for a fix and it was a failed hail Mary attempt. I followed this thread from the beginning and posted quite a bit while I was in deep trying to find a fix it this was about the same time Jesse Davidson was fighting for a buy back and traded a brand new Denali in for an F-150 at that point several competing dealerships knew about the vibration issue and were offering pennies on the dollar to trade or flat out refusing to take a GM trade in. Basically a few trucks got fixed with tires a few with shocks a few with drive lines and a few new rear ends or swapping the factory axle shafts for a set of Yukons but they are the exceptions and the majority have an inherent design flaw that is causing a third order harmonic vibration. Generally nth order vibrations are weak and absorbed by the mass of the machine/structure but when the input frequency matches the natural frequency of the machine/structure you have resonance and the vibration is magnified. So here we are with another batch of consumers trying to find a fix for a problem that a fix doesn't exist and GM barely acknowledges that a problem exists I'm sure many people have been told that your truck is "operating within the GM specification for NVH" an abitrary number that didn't exist until this issue did, I feel for you guys I really do I have been there. For anyone still trying to fix their truck because the cost to get out of it is too high, you first need to determine the frequency of the vibration you're feeling at a given speed. At 70 MPH a 12.5 +/- hz is a first order tire and probably a balance or runout issue. Multiply that by your rear end ratio say a 3.42 which is roughly 43+/- hz this would be a drive line that has a balance or run out issue. Now the 38+/- HZ this is a third order tire and this is the thus far unfixable chevy shake. The problem is that at 70 mph nothing on the truck is rotating at that angular velocity that's how you know it's a harmonic of the tire speed and there's a whole slew of parts rotating at the same angular velocity as the tires, harmonics are never a balance issue. My story; I wanted out of the truck for quite a while but wasn't willing to take the financial hit, gave up trying to fix it and just dealt with it. Vibrated like clockwork at 68 MPH plus. I drive a lot of California freeway, speed limit is 70 on most stretches, afters 3 years I had 70k miles on the truck and the vibration had gotten worse, to the point I loathed the truck. Add in the new issues that were popping up, leaking passenger side door seal, failed AC condenser, premature brake pad failure, the slide pins had stuck and were not allowing the inside brake pads to retract, outer pads had 60% left on them and inner pads were almost down to the rivets, return springs on the rear brakes were hitting the rotors making an awful screeching noise even though they still had about 60% of the pad left, failed navigation module, lower seat cushion would shift during turns and make a clicking sound, last but not least the paint was peeling off of the rear drivers side door due to bad prep, you could see the imperfections in the primer coat that were causing bubbles in the base coat. Enough was finally enough and I decided I was trading out regardless of the financial hit. Turns out I got a trade offer that was beyond my wildest dreams and jumped ship to a competitor (I'm intentionally not mentioning the brand to spare the haters the need to mention all the issues I'm going to have with __________ <---enter brand here) because they know a guy that bought one and the truck went rogue and castrated him in his sleep, then murdered his family exploded and burned the whole house to the ground. The fact of the matter all mfg's have their issues and all have their fanbois that will defend their brand to the death. I'll take my chances with another manufacture having issues and trying to fix them versus giving GM my money and having an issue that they haven't corrected in 5 years of production and barely acknowledge. Loyalty is earned not given and GM has done nothing in its history to earn anyone's loyalty, the few on here who have gotten buy backs had to fight tooth and nail to get them and even then GM tried to screw them. To anyone reading this that has the dreaded shake. I feel for you and if you find yourself driving at those speeds often ask yourself what your sanity is worth and just dump the POS if you can with the new GM platform out now you can bet there is no attention being paid to this issue from GM. Their customer care hotline is a joke don't waste your time, I was told they were working on it an anticipated a fix in a few months, over 3 years later and nothing.

My AC failed yesterday 48K miles. Seems GM has been using a condenser on this gen truck they know cracks and develops a leak.

i wouldn't be surprised to see a revised body mount that just happens to fit right into the K2 body mount perches without modification. Not an official fix the they would promote, but a word of mouth kind of thing that spread across the forums that people could buy a set of body mounts for the new trucks that smooth things out on the K2XX. GM then never has to admit to any design issue.

The steps have to fold underneath the body. When they are in the up position the perch for the body mount is directly above the step and you have about 1.25" of clearance. When the body moves up with the body lift the step moves with it but the mounting perch stays in place because its attached to the frame, your clearance is then reduced by however much you move the body. At 1.5" you can get just barely get enough clearance by trimming the larger washer on the body bolt. At 3 inches the step will crash into the body mount and will not retract, no amount of trimming can compensate for it. In the picture you can see that i had to cut half of the washer off for the step to clear and even then the step makes contact with the rubber bushing. You can see on my step in the second picture where it contacts the rubber bushing when it retracts. If you raise the body up any further you will hit the actual steel perch. The is one of 2 issues with a body lift and AMP steps. The other issue is the e brake cable equalizer. it also sits above the step and gets hit by the steps linkage when retracted, at least on a crew cab it might clear on a double cab but requires some modifications on the crew cab.

You will have more problems than just hiding the frame with your amps. The steps will also hit the body mount perch and will not retract. you can just barely clear the body mount perch with a 1.5" body lift and even that requires a little trimming to clear.

After scouring the web looking for project boxes I came to the same conclusion, A mold and potting them is the most economical, not sure how well they'll dissipate heat and potting will also make them irreparable.

I've heard the same thing, that they are having transmission issues. A friend of mine encountered a lady that couldn't get the key out of the truck because the truck thought the tranny was in gear when it was in park, couldn't start the truck either because of the same reason so he hit up another friend that's a mechanic and he said the colorados and canyons have been having a lot of transmission issues.

The 4 wd has an adapter where the 2wd tail housing would bolt that connects the t-case to the transmission. It's just a hollow piece, not to say the t-case doesn't have issues at the intergrated tail piece where the drive shaft conncets. If that really is the issue it explains why GM doesn't want to fix it. 2 grand a pop plus labor for the t case.

Here's something I noticed just recently though. My neighborhood is at the end of dead end street and everything just got repaved perfectly smooth and very little traffic. I let the truck idle in drive for a good 1/8th mile we are talking like 3 mph or so. There's a rough spot in something that is turning. Rough enough it'll shake water in a water bottle in the cup holder. Feels like a bad spot in a bearing. Problem is everything feels fine on the jack stands and spins smooth, if its a wheel bearing it's like it needs the weight of the truck on it before it becomes noticeable. If its somewhere in the drive train its like it needs a load to work against. Whatever it is I'm sure it will continually get worse until it fails then I'll know for sure whats causing it. Not sure i'll keep the truck long enough to find out I drive about 30 miles a day at speeds above 70, after 2 years I'm pretty tired of wasting time and money trying to fix it and making payments on a truck that I hate driving.

Nope haven't had anything changed in the steering, Is this something you have done?. I've read posts of people having a new improved steering bushing design installed which didn't help.

Vibrations at these speeds are typically linked back to out of spec ring and pinions. More specifically a pitch line run out issue on the ring gear. Too much variation on the back lash between the pinion teeth and ring gear teeth this is why you feel it during acceleration. Thanks for the info on the rear, I have been considering trying some lateral track bars on the rear this would definitely take care of front to rear movement now to convince someone to drive next to me at 80 mph and see if the wheels are moving front to rear before investing in some track bars.

Truth

Look on the bright side, at least you and a few others on here are only in leases. A lot of us have bought these pieces of $hit.

In case anyone wants more information regarding the PICO scope and how it works and its readings and what they mean, below are links to 2 videos posted by the professor at Weber State University Auto tech department. Videos are a little long but very well put together, Someone nearby WSU in Utah with a vibration problem in one of these POS K2XX should drop off their truck and ask him to use it as a teaching opportunity since GM doesn't want to solve the problem.

Most dealers will make you remove everything and put the truck back to stock before they will touch it a few have gone through the process which ultimately blames the tires and they go through countless number of tires finding the right ones to "fix it" that never do. Even if they are willing to work on it with the aftermarket stuff, if it gets to the point where they need to bring in a "GM field engineer" (which I believe is a very loose use of the word engineer) guaranteed he will point at the parts and say there's your issue and wash GM's hands of the problem. Save your money and go to a tire shop with a hunter road force balance machine and have them vector match the tires to the wheels to get the numbers as low as possible. If it still vibrates after that which will probably be the case it's likely not the tires.