Spring Clamps Reduce Rear Vibration

[14silverado4.3]

KLRV6, I brought this up before but not a lot of responses. I have a lot of Steering wheel shimmy and just crap ride from the front. Have you heard of spring oscillation? Was wondering if the shocks just don't have enough dampening design that allows the front coil springs to start to resonate... Would be neat to see that video?

 

 

These trucks transmit vibration, was never as evident as feeling a rear vibration only to find the left front out of balance.

 

The electronic power steering software allows for a certain amount of out of balance but it has to make its way out somewhere.... if it isn't the steering wheel it will travel elsewhere.

[JimmyJ_123]

 

Same with me perfect now ! Tightened the rear bolts I also changed the shocks to Fox 2.0 months back on the rear. The coil overs last weekend.

Edited April 12, 2016 by JimmyJ_123

[KLRV6]

KLRV6, I brought this up before but not a lot of responses. I have a lot of Steering wheel shimmy and just crap ride from the front. Have you heard of spring oscillation? Was wondering if the shocks just don't have enough dampening design that allows the front coil springs to start to resonate... Would be neat to see that video?

 

 

These trucks transmit vibration, was never as evident as feeling a rear vibration only to find the left front out of balance.

 

The electronic power steering software allows for a certain amount of out of balance but it has to make its way out somewhere.... if it isn't the steering wheel it will travel elsewhere.

I will post a vid of the front running stock shocks this week.

[ic3man5]

 

 

Just got around to this today. This is front facing back. I will work on a way to mount to the axle, right above the pinion. But for now..

 

 

Okay so I think your video finally shows what I was talking about in the front:

 

 

 

Kind of off-topic but this is a loop from like 2:39 to 2:41ish. You can kind of see the front looks like its bouncing/vibrating but the rear axle seems to take the bumps just fine. I want to say softer coil springs up front would fix this condition.

[KLRV6]

 

 

Okay so I think your video finally shows what I was talking about in the front:

 

 

 

Kind of off-topic but this is a loop from like 2:39 to 2:41ish. You can kind of see the front looks like its bouncing/vibrating but the rear axle seems to take the bumps just fine. I want to say softer coil springs up front would fix this condition.

The front has stock shocks on it. I just got the front 4600s in today, but am going to wait until I know about the driveshaft balance. I try to make sure the truck is as close to stock as possible when taking it in. It's kind of hard to say that shocks cause a bent/out of balance driveshaft though.

[DALaws]

trying to post a Pic of my drive shaft that has some markings on it from dealer. Interested to know what they may be? How do I post this image?

[14silverado4.3]

The front has stock shocks on it. I just got the front 4600s in today, but am going to wait until I know about the driveshaft balance. I try to make sure the truck is as close to stock as possible when taking it in. It's kind of hard to say that shocks cause a bent/out of balance driveshaft though.

There seems to be quite a bit of side to side movement in that clip. Look in the upper right hand of the clip, that is a lot of bouncing happening on the under of the cab?

[Dnt]

Crawled underneath and torgued the ubolts for the axle to leaf springs this last weekend got about 85 ft lbs with around 1/2 to 3/4 turn on each nut. I have driven for a couple days and can report NO difference at all. I ordered a set of leaf spring clamps and also ordered a couple of new rear shocks.I noticed that the Ranchos have a lot of rust on them (pic atatched). i will do leaf spring clamps and report back and then do the shocks next one step at a time to see if it makes any difference at all.

[Ron.s]

I don't know when GM started using stretch U bolts but we may have a problem messing with these. The 16's may have stretch bolts. Here's a little info I got from Google....this article is about engine bolts but the concept applies.

There are three types of procedures used for torquing: torque to yield/angle to turn; torque to maximum stretch yield; and torque to a specific torque number and hope it's correct.

Basically what it comes down to, is that torquing with just torque values such as foot-pounds or newton-meters is at best a guess at getting the torque correct. Depending on the type of fastener, materials used for both the bolt and the part it screws in to, cleanliness of the thread, lubrication used, TYPE of lubrication used, etc., the torque between two "identical" fasteners can actually vary by as much as 35% (or more) with the torque wrench having the same setting for both fasteners!

Many fasteners, such as wheel studs, water pump bolts, etc., are just there to make sure that the bolt is probably tight enough, and probably not too tight. These are the bolts that you reuse over and over without any problems.

Head bolts, as well as most of the bolts internal to the engine, are what are called stretch bolts (also known as torque-to-yield bolts). These are designed to be tightened to the point they physically start to stretch, usually by a few thousandths of an inch. This leaves them in a elastic condition, that allows very equal clamping forces to be applied to the part they're holding down.

When you tighten one of these bolts, the torque setting that is used is designed to get the bolt close to the point that it starts to stretch. The torque angle guage is then used to put the bolt PAST the point it starts to stretch and actually start to stretch it. You just can't accurately measure this with a regular torque wrench, thus the torque-to-yield/angle-to-turn method. The Maximum stretch yield method doesn't apply here, since you need A) A very accurate micrometer to measure the actual bolt stretch, and B) Access to both sides of the bolt, which you don't have on head bolts.

The torquing process is quite simple. You simply torque the bolt using a normal torque wrench to a pre-determined torque. Then, usually you'll warm things up by running it at idle, then let it cool back down and re-torque again with the torque wrench. After that part is done, the torque angle guage comes into play. The torque that the bolts are at after the regular wrench is theoretically just before the bolt starts to stretch. This accuracy depends of course on the factors mentioned above. To get the final torque AND stretch on the bolt, you tighten the bolt a given number of degrees of rotation. This is what the torque angle guage is for, accurately measuring the degrees of additional rotation (typically accurate to a degree or so).

The Reason For Not Re-Using Stretch Bolts

The reason is quite simple. Once you have stretched the bolt once, it never returns to its original size. This weakens the bolt, and if you try to re-use it, you take a risk of snapping the bolt in two, leaving the threaded part in the block, the top in your hand, and a complicated repair required. It's just not worth the risk to try to re-use old bolts.

You can get replacement bolts that are not designed to stretch at the torque required to hold the parts together.

There are two good reasons for using non stretch bolts. You want to re-use them in the future, and/or you have an engine that is either forced induction (745i running massive boost for example) or very high compression. Since the bolt is already at it's maximum stretch without losing strength, you don't want to put undue stress on it from a high compression engine and take the risk of a blown head gasket.

There is also a good reason for NOT using these bolts, and staying with the original OEM style stretch bolts. Non stretch bolts require retorquing after a few heat/cool cycles (usually specified at around 5-6 cycles), and may have to re-torque them anywhere from every 30k to 70k miles, depending on application. If you have a normally asperated engine, there's just no reason to have to do the extra work when normally you wouldn't touch the bolts again after they've been done properly with regular OEM stretch bolts. Also, stretch bolts tend to provide more consistent, even clamping pressure than the solid bolts do.

Edited April 13, 2016 by Ron.s

[oneandzero]

I don't know when GM started using stretch U bolts but we may have a problem messing with these. The 16's definitely have stretch bolts. Here's a little info I got from Google....this article is about engine bolts but the concept applies.

great info

[ic3man5]

I don't know when GM started using stretch U bolts but we may have a problem messing with these. The 16's definitely have stretch bolts. Here's a little info I got from Google....this article is about engine bolts but the concept applies.

 

Do you have a source for this? Also stretch bolts are mainly for the heads to allow flexing on heating and cooling of the engine which doesn't apply to the axle - I'm doubting this claim for now.

 

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.

 

I removed both sets of clamps today (4 total) and the ride is noticeably worse and probably worse than before I tightened the u-bolts. I think the leaf pack is just too loose and tightening it helps fight frame vibration as it transfers it into the axle and rear wheels also. I'm still convinced its coming from the front end and stiffening the rear end (which is what most are doing compressing against the overload spring) is fighting that.

[Ron.s]

 

Do you have a source for this? Also stretch bolts are mainly for the heads to allow flexing on heating and cooling of the engine which doesn't apply to the axle - I'm doubting this claim for now.

 

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.

 

I removed both sets of clamps today (4 total) and the ride is noticeably worse and probably worse than before I tightened the u-bolts. I think the leaf pack is just too loose and tightening it helps fight frame vibration as it transfers it into the axle and rear wheels also. I'm still convinced its coming from the front end and stiffening the rear end (which is what most are doing compressing against the overload spring) is fighting that.

 

Sorry I should have made my post more tentative as a heads up.

 

But that's the story I got at the dealership Yesterday. I had a long discussion with a tech and he explained the reason for the new torque wrenches with dial indicator and degree built in was to get a more accurate torque setting. He also said that the process stretches the bolt vs my understanding was that it stretched the threads. But the GM spec using degrees in the final pass may be a tip that they are stretch bolts. So calling BS at the dealership and arguing a little, I went home and spent a couple of hours researching and can't find anything to dispute his story. Mine were soft also about 40#'s but he said they wouldn't turn at 59#'s on his new whizbang Torque Wrench. that seemed fishy to me. I don't believe mine is off almost 20#'s but it's old and not a big name tool.

 

I can't prove anything one way or the other but I did look up the U bolt parts and fitment seems to stop at the 15's for those available on the web and through a GM parts source online. It may be because they haven't updated parts yet for 16's but for now it looks like the U bolt part is different in 16. I plan on stopping at a dealership parts counter soon to see what they have to say.

[oneandzero]

Maybe GM discovered a problem and changed it for 16. Who knows. Tightening seems to be working for some and thats good. Didn't help mine at all so thats not good but now at least maybe the rear axle won't fall off.

[ic3man5]

 

Sorry I should have made my post more tentative as a heads up.

 

But that's the story I got at the dealership Yesterday. I had a long discussion with a tech and he explained the reason for the new torque wrenches with dial indicator and degree built in was to get a more accurate torque setting. He also said that the process stretches the bolt vs my understanding was that it stretched the threads. But the GM spec using degrees in the final pass may be a tip that they are stretch bolts. So calling BS at the dealership and arguing a little, I went home and spent a couple of hours researching and can't find anything to dispute his story. Mine were soft also about 40#'s but he said they wouldn't turn at 59#'s on his new whizbang Torque Wrench. that seemed fishy to me. I don't believe mine is off almost 20#'s but it's old and not a big name tool.

 

I can't prove anything one way or the other but I did look up the U bolt parts and fitment seems to stop at the 15's for those available on the web and through a GM parts source online. It may be because they haven't updated parts yet for 16's but for now it looks like the U bolt part is different in 16. I plan on stopping at a dealership parts counter soon to see what they have to say.

 

I can't find any tool online that has a torque wrench and degree wheel built in, did you actually see this tool? I think your dealership is giving you the run around. My torque wrench is brand new and others on the forums have verified they are loose, using process of elimination the dealership is wrong unless they really do have some magical tool.

[Ron.s]

I can't find any tool online that has a torque wrench and degree wheel built in, did you actually see this tool? I think your dealership is giving you the run around. My torque wrench is brand new and others on the forums have verified they are loose, using process of elimination the dealership is wrong unless they really do have some magical tool.

I think my dealership has quality help but they are not acting independently...more like a mini GM. They follow GM guidelines and do little or nothing that GM won't pay them for. As a follow up to my visit they are contacting GM for further direction.

Here's a tool such as the one he described, they are only $944, ha ha. Don't think I will upgrade mine just yet!!!

 

Snap-on 1002TAA-CDI Torque and Angle Electronic Torque Wrench, 10 to 100 ft. lb.

Snap-on | Mfr# 1002TAA-CDI | Item# EW-25301-12