Spring Clamps Reduce Rear Vibration

Smickie500 · 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.

Pictures would help me put my U clamps on like you have yours......Only thing I have done so far is torque the axle U bolts ... I am anxiously ready to see if the spring clamps helps me.

Ron.s · June 5, 2016

Hope this will post as a pic. I don't use Photobucket much. To spread the pressure I think a thicker plate on top and on bottom is in order and I'll make it narrower so that I can get it a little closer to the axle. While removing my tire I found another example of GM torque gone wrong. On one wheel the lug nuts were pretty much the same torque but I didn't check exactly. On the other 2 were very loose, 2 in between and 2 so tight I had to use an extension on my flex handle to get them loose. My impact gun has never failed to remove any lug nuts when set on high but it wouldn't these two. Hope these weren't damaged because they were way over 140#'s. There was an earlier post about the way GM torques bolts but maybe not always, ha ha!!!

Now that I look at this picture it doesn't seem like I got them any closer by reversing them but they show less.

Edited June 5, 2016 by Ron.s

Ron.s · June 7, 2016

After some driving time I looked at my springs and noticed that the clamp on one spring has moved about 1/2". May need to add shims (like the factory ones) so that the clamp stays tight when the spring moves. I assume the shims were added to isolate sound waves to reduce road noise in the cabin.

Has anyone bought a different U bolt to replace the factory ones? I'm thinking that a grade 8, 5/8" bolt would let us increase torque and maybe eliminate the need for clamps. Since not all vehicles have this issue it's possible that some were over torqued and the bolt had stretched vs my assumption that mine weren't torqued enough. Any thoughts?

ic3man5 · June 7, 2016

After some driving time I looked at my springs and noticed that the clamp on one spring has moved about 1/2". May need to add shims (like the factory ones) so that the clamp stays tight when the spring moves. I assume the shims were added to isolate sound waves to reduce road noise in the cabin.

Has anyone bought a different U bolt to replace the factory ones? I'm thinking that a grade 8, 5/8" bolt would let us increase torque and maybe eliminate the need for clamps. Since not all vehicles have this issue it's possible that some were over torqued and the bolt had stretched vs my assumption that mine weren't torqued enough. Any thoughts?

If you get the dimensions you can probably try this: http://www.stengelbros.com/Square-U-bolts.htm

Random google search but it looks pretty legit. I want to do the same because mine are probably a little too torqued (110 ft lb). I've come to the conclusion the frame is just way to damn stiff to give it a perfect ride empty, I had one wheel off the ground in the back (uneven ground) and the bed wasn't flexing at all. Tempted to just throw 200lbs in the back and call it a day because it rides perfect with more weight.

morrislee · June 8, 2016

Guys, i had vibration around 120KM/h but I have fixed it by making sure the tire pressure will reach 240kpa when warm, so cold temp is about 228 to 236kpa. The factory 220kpa is NOT enough

Shredzy · June 8, 2016

Guys, i had vibration around 120KM/h but I have fixed it by making sure the tire pressure will reach 240kpa when warm, so cold temp is about 228 to 236kpa. The factory 220kpa is NOT enough

Converts to 34 psi.

ic3man5 · June 10, 2016

Guys, i had vibration around 120KM/h but I have fixed it by making sure the tire pressure will reach 240kpa when warm, so cold temp is about 228 to 236kpa. The factory 220kpa is NOT enough

3 PSI shouldn't be enough to do anything.

I've done 30-45PSI (206-310kpa) and it doesn't really make a difference besides gas mileage and ride comfort. I have a feeling your problem is going to resurface.

Ron.s · June 11, 2016

I agree, PSI increase didn't help mine, I always run 35 cold. For anyone looking for a deal on factory U bolts I found them at 32% discount. PN matches what dealer gave me for 2014-2016 LD's.

Factory U bolts: BOLT - GM (11569811)

List Price:$16.91 You Save: $5.44 (32% off) Sale Price: $11.47

http://www.gmpartsdirect.co/oe-gm/11569811

I'm going to remove one and see if I can find a non-OEM replacement-grade 8 in 5/8".

morrislee · June 11, 2016

3 PSI shouldn't be enough to do anything.

I've done 30-45PSI (206-310kpa) and it doesn't really make a difference besides gas mileage and ride comfort. I have a feeling your problem is going to resurface.

May have been my tires not worn correctly then

BO TIE 1 · June 12, 2016

Hey Guys was under my truck today and noticed that the rear leaf spring clamps are missing from the leaf packs.

Front of spring has a clamp

Rear of spring no clamp

Looked up a new spring on GM PARTS and the diagrams show the retainer clamps at both ends. Thinking this is a cause of axle wrap throwing the pinion angle out of whack. You guys with vibrations take a look and post up what you see.

Sent from my VS990 using Tapatalk

Edited June 13, 2016 by BO TIE 1

Ron.s · June 13, 2016

Update on U bolts. I can't find any U bolts smaller than 5/8" that are grade 5. There may be some but most 1/2" and 9/16" are grade 5. I don't think a 5/8" will work with our trucks without enlarging the hole in the lower bracket (maybe no big deal). The GM factory U bolts must be grade 8 based on the torque spec of 59# plus 130 degrees because max torque on a plated 1/2" U bolt is 52# grade 5 & 64# grade 8. Grade 5-9/16" is 75# and Grade 8-5/8" is 132#. There may be other torque specs that are different but this is at least a reference point. So any we have done over 64# are suspect and GM doesn't recommends replacing a U bolt once torqued.

Here's a link to a 9/16" U bolt that has a max torque spec of 75#, grade 5: http://www.stengelbros.net/5U-238S-916-X-2-516-X-8-34S-20-Square-U-bolt-with-nuts-and-washers_p_14298.html

This is what I'll likely try but first I'm going to visit another dealer to see what they have to say.

Ron.s · June 14, 2016

Hey Guys was under my truck today and noticed that the rear leaf spring clamps are missing from the leaf packs.

Front of spring has a clamp

0612161106.jpg

Rear of spring no clamp

0612161100.jpg

Looked up a new spring on GM PARTS and the diagrams show the retainer clamps at both ends. Thinking this is a cause of axle wrap throwing the pinion angle out of whack. You guys with vibrations take a look and post up what you see.

Sent from my VS990 using Tapatalk

No clamps on my "16".

tylerrmack · June 15, 2016

I have noticed vibrations throughout my highway drives. Any on brand new smooth pavement my water is always jostling. Looking through forumns I dont know what to think. Everyone has a different fix. Anyway im lookig into the suggestion for fix here. 2016 denali 6.2l shortbox. I figured the mag ride was going to be super smooth but its definetly not what i expected or something is wrong. Looked under my truck. No spring spacers like on other forums (why do some have these and others not?, is it different grades of suspension or did they come leveled?). Also i have marks on my rear axle and drive shaft. Do you think the factory did this or was there some sort of out of factory repair on it that i wasnt told about?

Ron.s · June 16, 2016

I have noticed vibrations throughout my highway drives. Any on brand new smooth pavement my water is always jostling. Looking through forumns I dont know what to think. Everyone has a different fix. Anyway im lookig into the suggestion for fix here. 2016 denali 6.2l shortbox. I figured the mag ride was going to be super smooth but its definetly not what i expected or something is wrong. Looked under my truck. No spring spacers like on other forums (why do some have these and others not?, is it different grades of suspension or did they come leveled?). Also i have marks on my rear axle and drive shaft. Do you think the factory did this or was there some sort of out of factory repair on it that i wasnt told about?

Interesting-you don't have spacers between the leaves in the center where the U bolts clamp? I wondered if they might be wearing/taking a set to let the U bolts get loose.

If you have a constant vibration (not just on rough roads) then this is probably the wrong thread for you. GM has a TSB mentioned in the Vibration thread that directs the dealer to a series of procedures that include RFB tires, Picoscope, etc. Consider taking it to the dealer for help. First I would document the condition that the vibe is worst including speed, road conditions and make a short video if you have a smart phone. If you have something out of balance in the drive train it will be worse at certain speeds and usually go away at others. Steering wheel =front end, usually tire or wheel. Seats= rear end including drive train and tires. I would tape a flag (like a sprinkler locater) you can buy at Home Depot to the seat or steering wheel for your video. You can buy 10 of these for a couple of bucks in various colors.

But trucks with a stiff frame like these will vibrate a water bottle and if it's not speed related then maybe compare yours to some others.

Ron.s · June 17, 2016

This will probably be my last post here.

Here's the end of my story. Dealer two couldn't get GM to do anything but gave me the name of a local shop that specializes in suspension and "lifts". (Boise Spring Works). They make their own U bolts, cold rolled. So quick trip to see what they thought and while talking to them they said that they didn't have access to stock for grade 8 bolts below 5/8" but that they torque their 9/16" grade 5 to 125#'s. Perfect!!! Thinking I would get hosed I told them to do mine, they had me back into the shop and went to work.. They removed the existing U bolts to find that the 9/16" would fit without any modifications. I also had them remove the spring clamps noted in a previous post. One guy built the U bolts while another removed the existing.15 minutes later they gave me a bill for less than $40. About like stopping for gas and far less $$ installed than I could buy anywhere. Not often that cost and service both exceed expectations in my world.

So thinking I would go back to them next week for new shocks, I did some quick testing. My suspension works the way it should now. RR tracks and other bumps are so much smoother, best riding truck I have ever owned. And now my drivetrain has tightened up. I was getting some slop on and off the gas and that is almost completely gone. I assume the loose U bolts were allowing "axel roll".

I'm so happy with my truck now that I ordered a tune from Black Bear.

And for those guys switching to Ford..... The shop guys told me several stories about Ford aluminum panels tearing, bed damage on a couple with $3000 repair tab. You don't fix aluminum, just replace it. According to them, GM is bad but Fords are worse and very costly to repair. And they have been adding another leaf spring to some Fords because they built them too light. I always take these kind of discussions lightly but just sayin!!!

Anyone that wants to try heavier U bolts-look for a local "spring works" business that specializes in lifts and builds springs and suspension parts for classic cars. Even if it cost triple it's worth it, IMO.