pm26

Yeah, keep crossing your fingers. I am sure it will have a major positive effect on the outcome. And if it is another shaker, go through this crap all over again.

Yes, mold can be very dangerous to your health. Recently I saw a case on Forensic Files where people living in a large house that leaked undetected behind the walls got seriously ill from toxic mold and almost died. Hopefully nothing this toxic would grow in your vehicle, but the air volume is small and you should get the leaks fixed ASAP and thoroughly dry all affected areas.

This is incredible. Looks like GM is trying to find out where the breaking point is.

Not all trucks exhibit any signs of vibration immediately. Some start vibrating after several thousand miles. So if you can arrange for a 4k miles test drive, go for it.

Cheaply made low profile tires create RF balance issues. The problem here is that GM wanted that big tire look, but at a cheap price. And that backfired badly. Another problem is that low profile tires do not belong on pickup trucks, unless they are used for show only. Low profile large tires on trucks are not practical, they expose rims to easy damage from potholes, and are downright useless for off-roading. And large diameter low profile tires are difficult to balance properly and usually special adaptors are required, which many tire shops and GM dealerships either do not have or choose not to use. Go to a Mercedes and BMW dealer to see how they balance low profile large wheels. Unfortunately, pickup trucks have been converted into luxury car substitutes to appeal to those who never intend to use them as trucks. GM has deleted drain plugs on radiators and rear differential, but illuminated vanity mirrors are now standard equipment on LT trim trucks? Just who are these trucks designed for? And this creates a whole new market for grossly overpriced vehicles loaded with cheap shiny gadgets, opulent looking (but cheaply made) interiors, and huge out of round tires mounted on crappy Chinese made rims. What's not to like when you are a truck manufacturer and people are willing to pay close to $60k for a half ton Mexican made pickup?

Yes, i forgot to add that the driveshaft speed will be the engine speed divided by transmission gear ratio for each gear. If that happens to be 1:1 (the top gear on some auto transmissions), then it is the same as speed of the engine.

You should go for an "enhanced" buyback instead. Unless you like the way these trucks vibrate. And don't expect someone who tells you that it is "normal" to fix it. How do you know the new one will not start vibrating after a few hundred miles even if it does not vibrate during the test drive? And the gear backlash can be adjusted. So if it is out of spec, it does not require replacement of ring and pinion gears unless there is something wrong with the gears themselves, or some unacceptable wear pattern is evident, which I consider very unlikely with a few hundred miles on the truck. It looks like they replaced the gears just to make it look like they are addressing the problem. And how do you know that they adjusted the gear backlash and gear contact pattern properly? Did they show you in writing what they adjusted it to and what the allowable GM backlash spec is? Might as well replace both of your headlights if they are aimed incorrectly.

If the vibration is caused by in an improper pinion shaft to driveshaft angle, the vibration will occur at the actual engine speed in any transmission gear. If the vibrations are caused by wheels, hubs, brake rotors, and/or axles, they typically occur at approximately 1/3 of engine speed (depending on your rear axle ratio). If the vibration frequency remains the same, it is typically a driveline problem, if the vibration frequency changes, the source is typically the engine or transmission. I am not familiar with GM's vibration analyzing methodology, but any GM engineer trained in vibration analysis should be capable of pinpointing the source of vibration with their equipment. The real question remains - are they really trying to find the cause and fix it or merely putting on a show? The main concern will of course be their acceptance/rejection criteria - do we know if these have been adjusted by GM to cover most of the troublesome trucks so they can claim that the trucks perform "within their design parameters." ? These are all questions that remain open at this time.

More of the same for HD GM trucks. This is really depressing for a potential buyer. http://www.gm-trucks.com/forums/topic/164602-2015-gmc-2500hd-crewcab-duramax-vibration/page-1 I am beginning to suspect that some of these vibration problems are caused by improperly machined rear axle housings. In this case the pinion shaft/gear and ring gear will not mesh at the proper angle and the vibration usually shows after a thousand miles or so. Also, the misaligned pinion shaft may cause the driveshaft to move in an eliptical manner, causing vibration, even if the drive shaft itself is good and properly balanced. Years ago i had a problem with an OMC/Volvo Penta SX outdrive on a new boat. After about 20 hours it started rattling like a bucket of bolts. it was rebuilt under warranty twice, all bearings replaced, gears reshimmed and it always ran for about 20 hours great after each rebuilt. Then the rattling came back with a vengeance. Finally I complained to the CEO of the company and got the entire drive replaced under warranty. Never had any problems with it again. The mechanic who rebuilt the drive strongly suspected bad machining of the old unit, which made rebuilding a waste of time. If something like this is the case with the axle housings on these trucks, replacing pinion and ring gears will fix the problem for a few weeks. It would also explain why the vibration does not show during test drives or first few hundred miles. If the housing is properly machined and the gear backlash is set wrong, the axle will typiclaly start whining after about 1000 miles of use. This happened to my 1995 Nissan pickup. The axle started whining only under load after about 1500 miles. Then they replaced the entire differential under warranty and all was quiet for another 1000 miles and it started whining again, but this time only during coasting (i.e. under no load). I would request a complete rear axle assembly if they wanted to replace just ring and pinion gears. There is a post by a Chevy Colorado owner who had his vibration fixed when entire rear axle assembly was replaced (see 2nd post in the link). http://www.gm-trucks.com/forums/topic/174291-2015-coloradocanyon-shakes-vibrates/

http://www.gm-trucks.com/forums/topic/177388-2015-yukon-xl-vibration-on-highway/ Suburbans seem to have vibration issues too. And they use coil springs in the rear.

GM has tendency to use the same crappy parts on any particular generation of their vehicles until they run out of those parts or change the design. Which is not encouraging.

I bet that by now it is a swearing wheel. Spending $ 60k on a POS would make anyone swear behind the steering wheel.

The problems some are experiencing with these trucks are a reflection of the new very disturbing trend in manufacturing. After manufacture of many parts and assemblies have been shipped to China and Mexico, now companies discovered that seriously cutting or even abandoning quality control means further profits. Or, they simply buy rejected parts at a fraction of the cost and mix them in with the good ones. So it seems they are shipping all tires and other parts, with certain percentage of the defective ones mixed in with the good ones. And not just GM - this is happening all over. Recently I bought a new utility trailer. I felt some vibration in the truck when pulling the trailer at 70 MPH, so i took the trailer wheels for balancing (they do not balance them on new trailers at the factory). First tire balanced fine with 1.5 and 3 oz of weights required, the other was a different story. It required 3.75 oz of weight on the outside, and 7.5 oz (!) worth of weights on the inside to balance. The weights on the inside are going half way around the rim! It is obvious that a tire like this should never have left the factory. But it was shipped as a serviceable tire from China, apparently among thousands of other blems. The guy measured the road force variation on the tire and it was 56 lbs! And this is a 205/75-15 tire! Now the fun part - how do I get a new tire and try to convince someone that 11 oz of weights to balance a 15 inch tire is way off the scale and the road force variation is off the scale as well? Do they even have an upper limit on road force variation for trailer tires? Maybe the criteria is "if it rolls and holds air, then it is good". It seems that some of you are experiencing similar quality related part problems on your trucks, including tires.

And with a lot more people.

Yes, there is a long term solution. Quit buying their vehicles until they prove that they have a quality built product. As long as people keep buying their overpriced junk, they have no incentive whatsoever to eliminate the known problems.

And in case the frame already had surface rust on it when coated with wax at the factory, the wax will last long enough to hide the rust until you get the truck home.

It just peels off like wax, especially after you apply it to a rusty surface.

Are you surprised?

If the tire actually slips on the rim when inflated to recommended pressure, then you have a major problem. Either the rim is oversized or the tire is undersized, or a combination of both. A properly fitting tire should not slip on the rim unless it is severely underinflated and the driver spins the tires hard on dry pavement).

Wouldn't this be more descriptive?

It seems inconceivable to me that if a vibrating truck was fully instrumented and put under load on a dynamometer, that GM could not figure out what the root cause of vibration is in each case and eliminate it by replacing the defective part or assembly. It seems that they really do not want to find out because, as it was pointed out several times already, it would cost too much to properly fix these trucks.

If that's the case, why don't all trucks vibrate the same? Only some percentage of trucks sold have the vibration problem, proving that instead of design issue, there is a batch of defective parts that were installed on these trucks, be it tires, hubs, axles, or transmissions.

They may work on the Peltier effect, but when assembled they all work on Pedro effect.

I did not realize water could crack (unless it is frozen of course). I wonder what the failure rate is on these water pumps.

If you have your wheels balanced, you can at least do something to feel confident that the balancing is reasonably good. First, ask them to calibrate the machine just prior to balancing the wheels. This can make a huge difference. Secondly, ask the technician if they have flange plates which will hold the wheel by the lug nut holes on the balancer. This plate mounting, in combination with a properly sized low taper cone or collet on the inside of the wheel center hole will give much better results than just using a centering cone to center the wheel on the machine. If they have no flange plates and use only centering cones, ask them not to use the cone on the outside of wheel if you have chrome clad wheels. The reason is, a cone placed this way is likely to catch on the cladding, not centering the wheel properly. Most usual centering of the wheel with the cone is using the cone on the inside of the wheel center hole, and rubber lined pressure cup (part of the shaft wing nut assembly) on the outside. Make sure the cone selcted does not catch on the wheel hole inner lip, if there is one, as this may cause a very inaccurate balance. If they have a road force machine like Hunter 9700, they can measure the road force variation. The machine will flag it if the road force variation is in excess of the preset number. In such a case the technician should remove the wheel from the machine, break the bead, and rotate the tire180 degrees on the rim to attempt to correct the excessive road force variation reading. (I wonder how many even try that?) Anyway, assuming the wheel/tire passes the road force variation test, let them balance the wheel. On these type wheels the usual mode is using hammer on weights on the inside of the wheel and stick on weights on the rim outside portion, just inside the wheel spokes. Up to three ounces of weights per side is about the practical limit for a decent 18 to 22" wheel/tire combination. After they balance the wheel and the wheel is spun again and the machine shows all zeros, ask the technician to loosen the wheel, rotate it about 30 degrees on the machine, then retighten it and spin it again. If all zeros show again, you can be somewhat confident that the wheel was mounted correctly on the machine and the balance will be good. When using flange plates, the blance is usually very consistent due to more accurate wheel centering. (Note: actual rotation of about 30 degrees is crucial. Merely loosening the wheel and retightening without rotating will not accomplish anything). If the balancing cone or the machine shaft are worn, the balancing will be off as it will not be possible to properly center the wheel. This is usually not the case, but it could be a factor with heavily used balancers. And finally, don't let them dazzle you with all that road force talk. Road force variation measurement is simply the degree of out-of-roundness of a tire. An egg shaped tire cannot be balanced properly no matter what. This is why it is important to reject the tire if the road force variation is too high. In the past they used thread shaving machines to "true" the tires, and they worked quite well. Now they replace the tires. Low road force number do not necessarily guarantee good wheel balance if the technician is sloppy or the machine not properly calibrated. So low road force variation and proper wheel balancing are not synonymous.