Rythmic humming

Sierra706 · April 6, 2017

Had fox coilovers, a 2 inch block, and a front differential spacer installed last week. Since then I've noticed a rhythmic humming which seems to emanate from the front of the truck. Not really noticeable when first starting off in the morning, but it begins to become apparent at highway speeds. Once it appears during the drive it will remain into lower speeds. Doesn't change during turns. Becomes higher pitched the faster I drive. Sounds a little like mud tires, but I'm currently on my factory bridgestones. The tires were rotated last week, but I did skip the rotation at my previous change. Prior to that I would rotate at oil changes.

Anyone have any ideas?

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calgator73 · April 6, 2017

Bad driveline angles

https://www.quadratec.com/jeep_knowledgebase/article-36.htm

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Justin101714 · April 6, 2017

Bad driveline angles

https://www.quadratec.com/jeep_knowledgebase/article-36.htm

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Agree!

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Chev-mekanik · April 6, 2017

I would eliminate the tires first though.

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Sierra706 · April 6, 2017

New ridge grapplers are going on monday, I hope the extra noise doesnt make it harder to diagnose. Im having a tough time believing its pinion angles. The differential drop didnt change the angle of the input shaft, just lowered it. So in theory both U-joints should still be at the same final angle. Am I wrong?

Its also not a vibration i can feel. Its just a noise

jflan23 · April 6, 2017

I had the same problem on my 2010 Silverado. Same set up, fox 2.0 coilovers, 2" block but no diff spacer. I also put duratrac's on it at the same time. I chased the same problem for a long time, new hubs (multiple). new half shafts with cv joints I was losing my mind. So I decided to trade the truck and put the stockt tires back on.

Wouldn't you know it the sound went away. It was the damn tires the whole time.

I doubt it's the angles, it's only a 2" lift essentially. Plus you dropped the front diff which effectively made the cv angles as if it were only a 1" spacer in the front.

My money is on the tires.

Sierra706 · April 6, 2017

I had the same problem on my 2010 Silverado. Same set up, fox 2.0 coilovers, 2" block but no diff spacer. I also put duratrac's on it at the same time. I chased the same problem for a long time, new hubs (multiple). new half shafts with cv joints I was losing my mind. So I decided to trade the truck and put the stockt tires back on.

Wouldn't you know it the sound went away. It was the damn tires the whole time.

I doubt it's the angles, it's only a 2" lift essentially. Plus you dropped the front diff which effectively made the cv angles as if it were only a 1" spacer in the front.

My money is on the tires.

We we'll see Monday. It seems to me that every time I rotate my tires they just end up being louder, with multiple vehicles now.

Another facet to the problem. I wanted to test the 4wd system to make sure something else wasn't going on. My actuator is now much louder than before, and at about 30mph on a straight road I heard a horrific grinding as it engaged. I quickly turned it off. In my driveway I tried again and it engaged and moved forward without any strange noises. Going to crawl under it tomorrow and see if anything looks out of place. I just changed the diff fluid myself, I hope the dealer didn't drain it and forget to fill it when installing the spacer!

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mjoekingz28 · April 7, 2017

Check your tires for scalloping or cupping.

ChevyRoofer · April 10, 2017

Had fox coilovers, a 2 inch block, and a front differential spacer installed last week. Since then I've noticed a rhythmic humming which seems to emanate from the front of the truck. Not really noticeable when first starting off in the morning, but it begins to become apparent at highway speeds. Once it appears during the drive it will remain into lower speeds. Doesn't change during turns. Becomes higher pitched the faster I drive. Sounds a little like mud tires, but I'm currently on my factory bridgestones. The tires were rotated last week, but I did skip the rotation at my previous change. Prior to that I would rotate at oil changes.

Anyone have any ideas?

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So you have adjustable coilovers & a front differential spacer? How thick is the spacer?

Sierra706 · April 10, 2017

So you have adjustable coilovers & a front differential spacer? How thick is the spacer?

1 inch

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ChevyRoofer · April 10, 2017

1 inch

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Why not remove the spacer? Not supposed to add spacers to adjustable coilovers.

Sierra706 · April 10, 2017

Why not remove the spacer? Not supposed to add spacers to adjustable coilovers.

Says who?

Not trying to be rude but do explain.

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ChevyRoofer · April 10, 2017

Says who?

Not trying to be rude but do explain.

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I've seen .25-.75" spacers on top of adjustable coilovers, but never 1".

You risk bottoming out the shock at full compression.

You also droop more after the spacer addition... so you'll need to watch out for the CV & UCA binding.

Spurshot had a good quote about spacers. http://www.gm-trucks.com/forums/topic/168768-leveling-bilsteins-vs-lift-kit/

I think you'll get a lot of different opinions on this.

But I do believe everyone will agree on this: It's not the static height of the lifted/leveled truck that exceeds the limit of the ball joint angle, it's the unloaded (extended) suspension.

Since the shock is the limit stop for the suspension, that means that lift/level spacers also allow the suspension (A-arms) to extend a similar additional amount as the lift when unloaded.

I think this is why some people have a given lift that seems a lot and have no problems with upper ball joints and others have loose upper ball joints prematurely. Some people may be driving very nicely on the streets and never or rarely fully extend the suspension. Also, my theory is that it's not premature WEAR, but really the ball is hitting the limit of the slot and trying to pry out of the formed socket and actually bending it open. I believe that's why some guys (GMT900) were experiencing loose ball joints in very low mileage after level/lifting, and some were not, even with the same amount of level/lift.

The Bilstein addresses this over-extend issue by not changing the extend travel of the suspension. It simply changes the static height by raising the spring pad.

I know I'm going to get some flack here, but my opinion is that, given the way I use my truck, I would not and did not lift the suspension with spacers more than 1 1/2 inches (I had a 3/4" thick spacer in the bottom of the OEM Ranchos for a number of months before putting on the Kings). I'm just basing this on my gut after reading all the reports when I had my 2008 and everyone was leveling and quite a number were reporting loose upper ball joints, some after 20,000 miles, some after 30,000, 40,000, etc.. I put Bilstein 5100s on the 2008 almost before the license plates came and set them one ring up from 0 lift (5/8"?). My ball joints didn't indicate any looseness until over 100,000 miles. The GMT900 suspension is the identical suspension on my truck (steel control arms).

Sierra706 · April 10, 2017

I've seen .25-.75" spacers on top of adjustable coilovers, but never 1".

You risk bottoming out the shock at full compression.

You also droop more after the spacer addition... so you'll need to watch out for the CV & UCA binding.

Spurshot had a good quote about spacers. http://www.gm-trucks.com/forums/topic/168768-leveling-bilsteins-vs-lift-kit/