abominable z71

Amplified by the leveling kit, Lol the lack of understanding of vibrations and NVH at dealerships is why you get responses like this. The dealer wouldn't show me the PICO results for this very reason, because they haven't a clue what they're looking at. I asked to see them and was told there was " a problem with the recording function and they could only see the analysis in real time". GM should have been left to drown in their sea of mismanagement and crappy bottom line engineering. I really don't blame the engineers, partly because I am one and know that often times our hands are tied by some accountant who has determined it's not cost effective to deliver the best possible product to the customer. In Gm's case it usually takes multiple deaths to get off their ass and do something.

The u joints on each end of the drive shaft have to be at equal and opposite angles to cancel out the angular velocity changes they go through during drive line rotation. Even though the drive line spins in a circular pattern the u joints themselves rotate in an elliptical pattern this creates velocity changes as they rotate. By having them at equal opposite angles the velocity changes cancel one another and the drive line spins at a near constant velocity. This is where the term CV joint comes from its a specially design joined to counteract velocity variation in drive shafts with unmatched angles like in the front half shafts on a 4wd. When the suspension compresses normally meaning both the front part of the spring in front of the axle and the rear portion of the spring behind the axle have force applied in the same direction the u joints keep the same angles relative to one another and everything is fine. Axle wrap is when the leaf spring is twisted meaning the forces applied to the front and rear of the spring are opposite of one another this cause the pinion flange to tip up and the angle of the 2 u joints no longer cancel each other and the velocity mismatch because of this angle change causes the drive line to vibrate.

Try using the spring clamp method it solved the hard acceleration vibration for me, Didn't fix the smooth road vibration at 70 mph plus. I believe the WOT vibe is axle wrap causing the driveline angles to get far enough apart to create a driveline vibration. I ended up ditching the clamps and putting Deavers in the rear and the WOT problem is still gone. I wouldn't recommend the deavers if you tow or haul often, otherwise it'll require helper airbags or timbrens for the extra weight because the deavers get rid of the factory overload spring. One thing to check for with the hard accel vibe if it was like mine it happened whenever the RPM's got over 4700 at any speed and was especially bad at 75 mph +, that must be where the engines torque curve flexes the springs enough to get the pinion out of alignment. I got a picture of the springs clamps in my gallery if you want to see what they look like. Any autoparts place has them on the shelf for about 15 dollars.

I'm not an HID guru but I have my degree in electro-mechanical engineering so I thought I'd share in laymans terms what is going on with the circuitry for your HID kit to help anyone that's trying to trouble shoot your install. There's is two different ways the factory head lights work on the GMC. Base models and SLE models that use the main head light as your day time running lights function slightly differently than Models with the LED's as the running lights (all SLT's and Denalis and SLE with the option) First are the non LED models the headlight bulbs are supplied 12 volts with the headlights in the on position whether auto or manual, when off and functioning as DRL's the computer modulates the signal meaning it turns the signal on and off really fast creating the dimmer glow for the DRL this is acceptable for resistance style headlights like halogens but not for HID lighting that uses and arc to generate it's light. Trucks with LED's only have voltage applied to the headlights when they are on whether it's manual or auto. The difference between them is what creates the need or eliminates the need for the capacitor link in the wiring of the HID kit which I'll explain next. The kit consists of several parts. The relay harness, the ballasts, the igniters, the burners (bulbs), and a capacitor link. How they all work together. The wiring harness connects the two relays directly the battery to provide a steady 12 volts to the ballasts. This is where the capacitor link comes in. The relays job is to physically decouple the truck wiring from your HID system by means of a magnetic coil. The relay is basically a switch, when it's off the ballasts are not connected to the battery when it's on the ballasts are directly connected to the battery. This is where the connection to your factory wiring comes into play as well as the capacitor link. When the head lights are turned on the signal that would normally go to your factory head light bulb is now routed to the coil side of the relay, the coil energizes a magnetic switch in the relay that closes and connects the ballasts to the battery, when the head lights shut off the coil de-energizes the magnetic field and the switch opens. Now for the capacitor link if you have a model without LED lights you need the capacitor and here is why. Because the signal is pulsed meaning turned on and off really quickly the coil on the relay is going to open and close really quickly as well which would also pulse the signal on the load side of the coil which is what connects the battery to the ballasts. This creates a problem for the relay as they're not designed to do this especially DC relays this also creates a problem for the ballast which are designed to control and regulate the incoming voltage before sending it to the burners more on that later. So what is a capacitor and how does it help our DRL situation. A capacitor is like a storage tank for electrical current it will accept current coming in and release it slowly (much more to it but irrelevant for this discussion) So the choppy incoming DRL signal comes into the capacitor and is released as a steady flow to the coil side of the relay keeping it from opening and closing allowing the connection on the load side to remain closed and steady. Without DRL's the signal from the factory wiring is already a steady 12 volts and the relay functions as normal. This is why the capacitor is not required on the SLT's or Denalli's, but the kit is a one size fits all and the capacitor link is always included. If everything is wired correctly with head lights turned on, the two leads marked ballast should have 12 volts measured across them using a multimeter. Check here first if the lights do not come on to make sure voltage is making it's way to the ballasts. If not make sure you have voltage going into the relay on the coil side. This is the connection from the factory light plug into either the capacitor link or into the patch cable. A trick for checking if the connection is bad at the connectors themselves. Using your meter put the negative probe directly to the battery ground take a really fine sewing needle and tape it to the positive probe of your meter and use the needle to pierce the insulation of the positive wire and check for voltage between the connectors this can help pinpoint the bad connection. Now to the ballasts, The factory halogen lights use a resistive element that gets hot the heat starts the halogen cycle in the bulb and creates the light. The wattage is controlled by the resistive element itself (kirchoff's laws) the voltage drop created by the resistive element creates current flow. the current multiplied by the square of the resistance equals power ie a 35watt bulb or whatever the bulbs rating may be. HID's utilize an arc to generate the light and the arc will continue to draw more current if it's not regulated. This is the ballasts function, this is why with the HID kit you are buying has ballast's rated at either 35 watts or 55 watts and the burners themselves are only rated by temperature or color 4500K 5k and so on the burner itself has no control of the wattage like the factory halogen bulb. The last piece is the igniter, HID lighting typically has long start-up time's and long gaps between restrike meaning the time required between turning the lamp off and back on again. The igniter eliminates this by momentarily providing a much higher amount of power to get the bulb up to full operating temperature and minimize the time required for restrike. The last piece is the burner or bulb. Unlike the halogen that has a resistive element to create heat an HID burner uses and arc created by a momentarily supply of really high voltage potential across two electrodes just like a spark plug. this arc ionizes gas in the bulb typically xenon the heat from the ionized xenon vaporizes salts in the bulb and fails the resistance between the electrodes and the ballast kicks in maintaining the proper voltage and current supply to main a stable arc whether it be 35 watts or 55 watts. The odds of getting 2 bad ballasts, 2 bad igniters and 2 bad burners is extremely unlikely and because the voltage post ballast can hit 20k - 25k volts I would not recommend checking these with a meter if you still have problems and have a steady 12 volts to the ballast try each ballast, igniter and burner combination. but the odds are the problem is before the ballast.

This is truly the step that needs to be taken, apparently GM or the dealer does not want to invest in the time required to do this. It would help locate the are causing the issues. You could do it with a single sensor and just move it from location to location. The problem for the average guy is a vibration analyzer with say 4 inputs the acclerometers and cabling is going to run about 10 grand on up. I used to work as a plant engineer and we had a unit made by SKF for balancing high speed turbo machinery (turbines, compressors, fans and such) it had 4 inputs and cost 30 grand although it had other features for balancing and shaft alignment. I've been looking into it and for the DIY guy your best bet is to find an old EVA2 unit, this is what GM used to use before the PICO scope. You can pick one up on ebay for about $400 bucks single input I believe but you could move it from corner to corner and different frame locations to help narrow down the source. As far as the wheel dyno goes, dyno time tends to be spendy and not readily accessible but would eliminate the road surface as a source. Right now as I type this my truck is down at a local tire shop and the tires are being trued and balanced on the vehicle if it still shakes after this I'm going to say it's almost impossible they are the source, and it might be time to purchase an EVA2 to find the source because the dealer surely isn't going to log in the time to do it.

I found two local shops that do tire truing. Since I took some run out measurements and found as much as 3/32" inch on one tire I'm thinking about giving this a try to eliminate it as a possible cause. Also my new rear leaf springs from Deaver should be here tomorrow according to UPS going to try and install them Thursday. I doubt the springs will change anything but hey I'm at the throwing parts at it phase right now. However the tire truing might be the ticket. Ultra sensitive truck might require very round tires, $49.95 for all 4 is worth a shot, most everything I've read about it they say once you have it done the first time, you'll have it done every time you get new tires.

Already tried this. The truck is a real bitch to drive without power steering it takes some serious muscle at low speeds. But it didn't do anything to the vibrations at freeway speed. You can try it yourself just roll under the front end and on the passenger side unplug the power cable going to the electric assist motor. You'll get a message in the dash to service the power steering system and to be careful because the truck will be difficult to drive.

I think this is might be do to the larger tires they are running. The tires would be turning at a lower frequency at an equivalent speed and may be keeping them just out of the vibration range. Like the difference between 68 and 70 mph on these trucks. At 75 mph a stock tire is turning at 787 rpm or 13 hz. A 35 inch tire at 75 mph turns at 720 rpm or 12 hz. A stock tire turning at 720 rpm just happens to be 67.9 mph or the magic number where these trucks typically start to shake. What this means is far as rotation frequency is that a 35 which is typical for a 6 inch lift at 73 mph is has the same input as a stock tire at 64 or 65 mph which typically doesn't induce vibration. Just a theory but the math supports it, if and only if the problem is resonance which is frequency dependent.

Nice truck, I saw it in the body lift forum and that's what sealed the deal for me, ordered the body lift and put it on that weekend.

Polyurethane is a much harder material then natural rubber which is why your ride got worse instead of better. Although you can get softer shore hardness in poly to behave more likes its rubber counterpart. The problem with the mounts on these trucks is that they're a shear style mount that gm used to give the truck better handling which worked, this trucks handles better than any others on the road, I believe motor trend or car and driver made the same comment in their tests. The problem is the mount is very rigid laterally. I gave them a close look while I was installing my body lift and I'm not quite sure how you change them out. Although I didn't try to remove one either, one thing for sure it's definitely more than just a rubber puck sandwiched between the body and frame.

I redlined your post, it's almost like I wrote it myself, I'm sure others on here feel the same way. The worst part of it all is I like everything about this truck more than any of the others on the market but the vibes are killing it.

I don't think anyone with one of these vibrators will ever give GM another chance, and hopefully people that read one of these forums before purchasing steer clear of their garbage vehicles as well. They won't even formally admit that there is an issue that they can't fix. I think if they formally admit it they know that quite a few more people that don't even realize they have a truck with issues will discover that they do whether it's because they never take the truck on the freeway and see speeds of 70 mph or because they just assume it "rides like a truck" which is bs, I've owned numerous trucks many of them GM and they never rode like this, even with mud terrain tires they didn't vibrate.

Did the same thing, lowered the pressure on my 10 ply tires from 42 to 32 and significantly lowered the vibrations as well. Problem is the truck now handles like garbage leans in the turns and just has a squishy feel to it. Anyone else that has had the vibes for a while check the lower portion where the struts welds to the mounting eye that connects to the lower control arm. Mine are starting to crack. They are not the original Rancho's that came on the truck but 6 month old Rancho RS9000's, I contacted Rancho to see if they will warrant them. Just curious if anyone else with the vibes is seeing cracks in this location on the factory struts. Part of it is poor weld quality where there was a void left from the weld process that has helped facilitate the crack propagation. Rancho's "lifetime warranty" doesn't include their quicklift struts they are covered by a laughable 90 day limited for work and material defects. But I'm giving them a chance to stand behind their product. These things only have 8000 miles on them. We shall see how they handle it.

GM needs to look at redesigning their body mounts or rebracing the frame to change the overall stiffness matrix or resonant frequency of the frame itself. I find it hard to believe they don't have access to software and computing power to run an FEA on it, they know what the vibration frequency and force vector is that is causing the damn thing to resonate. Maybe they should sub contract the job to Honda at least they are acknowledging and working on fixing the CRV vibrations. The worst part is they expect the consumer to accept it because they are too inept to fix it. Almost 3 years since they released this platform and who knows how many years in development before that at least 3. The first nuclear bomb was created in less time. Should have let them go bankrupt, this is the kind of crap that is the reason they were failing in the first place. I wonder what the executive bonuses looked like this year considering they have been selling the crap out of these trucks even though at serious reduction to MSRP, it just goes to show how over priced these trucks are in the first place because you know even at 10K off they're still making money. Sorry, that's then end of my diatribe.

This actually is a pretty common way to troubleshoot vibration from the driveline due to imbalanced mass. Measure about 6 inches from the rear pinion yoke and then using a sharpie divide the circumference of the tube into 4 equal parts 90 degrees apart and draw a small mark number them to keep track if it helps. Put your hose clamp around the drive line and tighten it up so the screw portion of the worm gear is centered on your first mark. Drive the truck and see how it feels, then rotate the location of the clamp to your next mark and see if things are better or worse when driving it. When you determine which mark feels the best you can then adjust in small 1/2" increments from there to dial it in. Add a second clamp right next to it after that to see if the extra weight improves things, you can then repeat the process for the front end of the shaft by the transmission/transfer case u joint but this is typically not necessary. Often times this is done using a strobe light and vibration analyzer like an EVA2. That eliminates the need to drive the truck between each adjustment of the clamp location. If you search youtube for EVA driveline balancing there's a good video from a college autoshop class that shows the whole procedure using an EVA2. Just do the same thing but drive the truck between each adjustment, your butt will tell you what to do from there.

It's not a wheel and tire issue at least for almost all. a few people have the vibe fixed by wheel/tire replacement majority of us have had countless road force balances and numerous wheel and tires changes with no affect. If you look at all the truck that are posted in the wheel and tire section and lift kit section on this site it's obvious most don't vibrate and never did. A lot of people running 10 ply tires and mud terrains with no vibrations and there is no way that everyone of those people had their new tires road force balanced and my guess is for quite a few most of them would have tires with high road force variation with no vibration issues. The problem is something else, the one problem is there hasn't been an established vibration frequency at a particular speed. Everyone states it vibrates at around 70 mph on up but are we all experiencing a vibration at the same frequency. If we can establish that everyone is feeling the same thing we could assume it's the same faulty part if we are experiencing different frequencies at the same speed it's a different source from truck to truck. Mine vibrates at 40hz at 75 mph, which is exactly 3 times frequency of the tires at 75 mph. rules out the drive line, transmission and t case. Leaves wheels, tires, hubs, rotors, axle, differential, cv shafts, hub bearings. Already removed the cv shafts didn't affect things, tried multiple wheels and tires with no change, dealer checked rear diff said everything is good (not sure I believe them). Leaves hubs, rotors, axles and bearings. I need more sophisticated equipment to pinpoint the problem but haven't made the purchase. I just used my phone with an app called VibSensor by now instruments and software (free on android) to determine the vibration frequency, the console shakes plenty at 75 to give a good reading. A good vibration detector with an external accelerometer could be placed at different locations on the truck to narrow down the source. Why GM or the dealership doesn't do this is beyond me. GM if your reading this send me one of your PICO scopes for a little bit and I'll fix our mistake or do you know what the problem is and it costs too much to fix?????

Did the 16 vibrate or did you get rid of it before it got a chance to start vibrating?

Sorry to hear it, but just a heads up gm customer service isn't worth a shit. They might help set up an appointment but they are low level and pretty much useless, just like the rest of the company from the top down.

Lol, Everyone knows grand cherokees are pieces of shit.

Yeah I feel you, 4 months after I bought mine they released the new design with new features, I guess that awlays the problem you face when buying most things just hurts more when it's a $50k truck that is already a POS 2000 miles into its life

Gm obviously has no intentions to fix the issue so someone crunched the numbers at corporate and obviously know they are going to lose customers but it must be less than the cost to fix it.

Seriously going to look into just eating the loss and looking at a tundra , whether I keep this shit box or not it will be the last gm product I ever purchase

Not really at freeway speeds. Still preventing the vibrations during hard acceleration but very little affect on the freeway vibe

I agree, it seems like these numbers are constantly changing depending upon variables that cannot be controlled, ie. temperature, atmospheric pressure, tire wear and so on, it would explain why the vibrations seem to be different on the same stretch of road depending on weather conditions. my dad just bought a 15 silverado even though I advised him not to (die hard chevy has had at least 1 of every body style from a 53 5 window to the 15 he just bought). If it doesn't vibrate after 5000 miles or so I'm going to start swapping parts and the first thing is going to be the rear end.

Nope, second set is still sitting on the workbench, it has been raining here for the past 4 days which is a good thing because we need the water her in CA. Unfortunately it puts most testing on hold because traffic on the freeway slows a bit and gets congested making it hard to get a nice stretch at 75 mph. You have the 305 55 20 XL g2's in 4 ply correct? Any difference in vibration between them and the factory tires? I noticed my vibration is more pronounced with the 10 ply toyo's I was thinking of making the switch to the G2's in a 305 60 18, whats the road noise like with them? The at II extremes are pretty load for an at tire much louder than the BF Goodrich KO2 for sure, never been in a truck with the G2's.