Spring Clamps Reduce Rear Vibration

Smickie500 · April 29, 2016

I measured my u-bolts and the thread diameter is 9/16". A grade 5 u-bolt is 90ft/lbs. Mine weren't even at 30ft/lb breaking force which is 3 times less than it should have been.

Question....The bolt itself measures 1/2" so shouldn't max torque be 65#? If these are cold rolled 1/2" with 9/16 thread then the bolt will stretch at that theoretical max. Since we are testing an installed bolt and haven't applied never seize or other lubricant friction might allow a slightly higher torque number but IMO 70# might be the upper limit.

I got around to checking mine today....They were also around 20 or 30lb so I torqued them to 60lb. I will report back in a few days after a road trip.

Ron.s · April 29, 2016

I got around to checking mine today....They were also around 20 or 30lb so I torqued them to 60lb. I will report back in a few days after a road trip.

This doesn't make sense to me that there are so many that aren't torqued properly. GM went to the trouble of specing a more accurate way to torque using degrees to finish. Those torque wrenches are spendy at almost a grand each for a SnapOn....I'm wondering if the bolts have defective metallurgy and are stretching or were torqued too much at the factory and the bolt is failing. My 2014 had the same spring setup (I think-looks the same) and no issue with it vibrating.

15silver · April 30, 2016

Bolts at the factory are run up with (used to be air powered) electric torque controlled guns. Each gun has a controller that monitors the torque and shuts the tool off at target torque. Also can tell if it was cross threaded (not enough degrees). Fastening strategies are specific to the fastener, some are straight torque, some are torque and angle. Its a science, and the controller cal's are set by corporate. The controllers also record the values and report them to a host computer for monitoring the site wide performance of the entire process. Failed fastening operations set a light, and the QT has to come by to inspect, repair with a calibrated hand tool.

There's no guess work, or slack employee input. They try to eliminate operator error for every build operation. Many fasteners are MVSS spec, and have to be recorded by law (well all are recorded now). Part of GM's quality initiatives.

Possibility of poor materials that stretch over time, and this would get tagged by the warranty process. That would generate an internal investigation, and possible recall or TSB. Be assured when the vehicle left the factory, the fasteners were at design spec.

I agree the dealerships are the weak link, as the tech's experience and perseverance will determine whether the customer is satisfied. This is a tough problem though - yet they do have vibration monitoring tools available to them. Possible it needs to be escalated to district rep before they really dig in. Onus is on the dealer though to resolve. You install aftermarket parts and complain, that complicates the process, and is an easy out for the dealer - but you knew that going in. Dealers push back because they only get so much $ back from GM for a certain repair code. You need to request escalation, if they don't get it first shot, or 2nd at most. Its a game. I hate it, but if you know the game, at least you can hold them to their playbook.

Ron.s · April 30, 2016

Bolts at the factory are run up with (used to be air powered) electric torque controlled guns. Each gun has a controller that monitors the torque and shuts the tool off at target torque. Also can tell if it was cross threaded (not enough degrees). Fastening strategies are specific to the fastener, some are straight torque, some are torque and angle. Its a science, and the controller cal's are set by corporate. The controllers also record the values and report them to a host computer for monitoring the site wide performance of the entire process. Failed fastening operations set a light, and the QT has to come by to inspect, repair with a calibrated hand tool.

There's no guess work, or slack employee input. They try to eliminate operator error for every build operation. Many fasteners are MVSS spec, and have to be recorded by law (well all are recorded now). Part of GM's quality initiatives.

Possibility of poor materials that stretch over time, and this would get tagged by the warranty process. That would generate an internal investigation, and possible recall or TSB. Be assured when the vehicle left the factory, the fasteners were at design spec.

I agree the dealerships are the weak link, as the tech's experience and perseverance will determine whether the customer is satisfied. This is a tough problem though - yet they do have vibration monitoring tools available to them. Possible it needs to be escalated to district rep before they really dig in. Onus is on the dealer though to resolve. You install aftermarket parts and complain, that complicates the process, and is an easy out for the dealer - but you knew that going in. Dealers push back because they only get so much $ back from GM for a certain repair code. You need to request escalation, if they don't get it first shot, or 2nd at most. Its a game. I hate it, but if you know the game, at least you can hold them to their playbook.

What you say makes sense but then why are so many loose? The spec of 59# + 130 degrees. Would leave you around 70 and using the reverse torque method were 40 at most. My torque wrench may be off a little but not that much. And taking mine to 70 got rid of the vibration. I guess it's possible that there is som movement letting the parts take a set reducing the torque but that's too much dif.

15silver · April 30, 2016

What you say makes sense but then why are so many loose? The spec of 59# + 130 degrees. Would leave you around 70 and using the reverse torque method were 40 at most. My torque wrench may be off a little but not that much. And taking mine to 70 got rid of the vibration. I guess it's possible that there is som movement letting the parts take a set reducing the torque but that's too much dif.

Well it makes sense because that's the way it is. Worked there 24 years, and the fastening system is one I supported for quite a while. I'd discuss your experience with the service dept, and perhaps 1-800 customer service. The torque spec - you found that where? Just curious, not I doubt your assertion. 59lbs and 130deg isn't the same fastening strategy as 70 ft lbs. Personally, I'd hold the dealer to the heat - mention what's worked for others and ask them to explain why/why not this is a good strategy. It seems to have worked for some on this thread, and not others. Trying to out think the engineers who designed the vehicle takes more than anecdotal experimentation - however I find value in seeing what others have tried, and sharing that info for others to try at their own discretion. There are lots of modifications here that are great for self-customizing projects, but don't raise safety issues. Changing torque values may be a good thing, but not without consulting the 'experts'. Over torquing stretches the fastener, and weakens it. Will it fail tomorrow? maybe not. Next time you re-tighten it? maybe ... kinda russian roulette. Just something to ponder, then one can make their own choice - but be prepared to live with the consequences.

One thing to consider is when assembled, everything is new and clean. So if you were to take the time to remove the nut, clean the surfaces and threads, then re-torque to spec, its not inconceivable it'd take less torque to achieve the same fastener tension, than with rust and dirt.

Edited May 1, 2016 by 15silver

15silver · May 2, 2016

Found this - nice explanation of torque vs torque and angle.

GsBowtie · May 7, 2016

I have no vibration issues, but sometimes feel a clunk when shifting from forward to reverse and sometimes when I put my truck in gear before the rpm drops to normal idle.

So I decided to check my u bolt torque. Mine were in the neighborhood of 50 ftlb. Not enough in my opinion, especially considering I tow a 6000 lb travel trailer.

I also didn't like how the rear portion of the leaf spring did not have any clamp holding the two leafs together from the axle all the way to the rear, so I put a clamp on the rear about 3" from the end of the second leaf. So now at least the front portion of the leaf has the factory clamp, and I have the advance auto one on the rear. I painted the clamp black before I installed it to prevent rust. I'm interested to see if this will get rid of my clunking. If it has an adverse effect I'll let you know

Dnt · May 8, 2016

Have left the leaf spring clamps on approx 5in in front of the axle for about 3 weeks here. No difference in the vibration (FYI HERE) I will have to say the clamps have really helped with the low speed clunking. It happened before rather regularly on slow speed downshifts. It has all but disappeared much more enjoyable to drive.

DALaws · May 9, 2016

What size is the factory U-Bolt nut? I'd like to stop by on way home from work to pick up appropriate size socket.

GsBowtie · May 15, 2016

Update; no real change (with vibration, i had none before ) i can tell on my truck with u bolts torqued to 79 ftlb and my clamps on the aft portion of the spring, 3" from the end (top 2 springs only)

I do believe one change i do notice, unless it's just my mind wanting me to, is the forward to reverse clunk is gone and the movement i felt sometimes on the transition from my shop floor to driveway seems better.

This could also just be in my head, but the rear suspension seems more solid now as well. All in all a good change for me, so thanks guys!

Edited May 15, 2016 by GsBowtie

650h1 · May 17, 2016

Anyone try using spring clamps to balance their driveshaft and see if it improves their vibrations? I'm thinking of trying it...

ic3man5 · May 17, 2016

I took my clamps off completely, the ride is awful now that I tightened the ubolts down with the clamps on. Clamping to the very rear just the two leafs seemed to help a little bit but was bothering me because it was visible and those autozone clamps look very cheap.

I noticed when I load the bed with some weight (200-300lbs) the ride becomes extremely smooth and awesome. I moved a refrigerator and had it all the way towards the tailgate. Thinking about adding some sand bags in the bed and seeing what that does.

Edited May 17, 2016 by ic3man5

CbrownGT · May 17, 2016

Read through the thread. Just started having hard vibrations at 70+ mph. 31k miles. I have 285/65/18 AT tires so there was already the slightest vibration, so I know there's an issue since I really felt it. Coffee cup was bouncing all over the place.

So I have a couple questions: . I think I'm gonna try torquing down the u-bolts first. I have torque sticks for my impact gun so it should be easy.

I drive on really really rough terrain for my job, so I question whether spring clamps and hardware would really hold up over time, especially with western pa winters and all the salt used. Anyone have an opinion on this?

southern_sierra · May 18, 2016

I took my clamps off completely, the ride is awful now that I tightened the ubolts down with the clamps on. Clamping to the very rear just the two leafs seemed to help a little bit but was bothering me because it was visible and those autozone clamps look very cheap.

I noticed when I load the bed with some weight (200-300lbs) the ride becomes extremely smooth and awesome. I moved a refrigerator and had it all the way towards the tailgate. Thinking about adding some sand bags in the bed and seeing what that does.

I have mine clamped about 4 inches in front of the axle block spacer. This made the ride much better or less harsh in the rear. I moved them to the rear just to see what would happen and made the ride much rougher, so I moved them back to the front.

Ron.s · June 4, 2016

Maybe the answer at last....

After a typical dealer visit I decided to try one last thing before replacing the Magneride shocks. First some history;

I had the exact same truck in a 2014 that did not vibrate and had a good ride but didn't have Magneride shocks. My 2016 did not have a rotational out of balance vibration but one cause by the suspension and only when I hit rough sections of pavement such as frost heaves, asphalt seams and concrete roads that have a tendency to heave. So my vibration came and went and was more of a rolling quiver at low speeds and a full vibration at higher speeds. The entire truck shook. Intermittent and after a while I realized that it only happened on rough sections of road.

First I tried the cheap Auto Zone spring clamps at various positions front and rear of the axle. This helped but still wasn't quite right. Settled on about 6" front of the axle as the best and no second set of clamps.

Second I torqued the loose stock Ubolts to 70#'s and that helped a bunch but There was still a "quivering" feel at lower speeds when I hit a series of bumps and the shocks weren't working right. Also ride was worse so I removed the spring clamps. This was now the best it had been but still not quite right and got a little worse after a few weeks. Now the high speed vibration (75MPH-80MPH) was almost gone.

Spring clamps had one thing that bothered me. They compressed the overload leaf and the other springs together. OK with some weight in the truck but not so good empty. So on to my Third attempt. I took the spring clamps and flipped them upside down so that I could get them tight against the other bracket for the factory Ubolts and put a clamp on either side of the axle. I torqued them to 25#'s and could see the cheap bracket bend. I also added a flat washer and better lock washers along with thread lock. I can now feel the shocks work and the ride is the best it's ever been, even better than my 14. I'll be test ing some more over the coming weeks and if it works will have narrower brackets made -both an upper and lower for each clamp. I will post a picture tonight, the doorbell just rang.