FIXED - Vibration Only On Acceleration - New 2018 2000 MIles

TwoBallScrewBall · February 18, 2019

So we bought this truck new on December 28th. It's got about 2500 miles on it right now.

Noticed on the highway this weekend, that the truck has a pretty serious vibration when under heavy load, especially with accelerating on the highway with full throttle.

I don't remember this being there earlier than this weekend, however it's my wife's truck and she drives it locally most of the time. And the times I have taken it, I'm honestly not sure if I had ever gone full throttle with it, especially at highway speeds.

Only happens under load. Feels very much like an engine miss, but there are no codes, and it does feel more like it's coming from the back of the truck.

I have just checked U-joints, no slack and the bolts on the rear pinion straps are all tight. No dents in the driveshaft that I can see.

Mods I have done so far that could be related: 3" Front Spacer Lift, 3" rear blocks (in place of the stock 1.25" blocks, and muffler delete with resonator still in place. I used flat blocks, not tapered, after reading about lots of folks having issues with the taper blocks. I do have a set of taper blocks I can throw in to test with. As well as the stock blocks and U bolts.

I'm strapping a GoPro to the trans crossmember, facing backwards, to watch the driveshaft and the exhaust when it happens. GoPro is charging right now, haven't touched it in months. Will post back up if I see anything in the video. Kind of feels to me like it could be the exhaust vibrating, and perhaps cutting out that giant heavy stock muffler along with the specific bends my guy put in the straight pipe maybe causing some weird resonance. Or maybe it's just another cursed vibrating Silverado.

I had a 2016 Double Cab for 3 years and 25000 miles and it ran smooth as silk from the day I got it to the day I traded it. Kind of miss it right this moment, it might have been a unicorn.

Edited February 22, 2019 by TwoBallScrewBall

michigan2500hd · February 18, 2019

I noticed when I had swapped out my stock blocks for 3" blocks I had the same feeling you did. Even when stopped and giving it gas to get over a hump I had going into the garage. I went back to stock and it lessoned quite a bit. Now again I'm wanting to lift the rear a little bit I'm thinking 2" blocks this time.

TRKLGND · February 18, 2019

Most mods come with "undocumented features". In the IT world (where I come from) they are also known as bugs.

1SLOW1500 · February 18, 2019

Axle and pinion angles. Or axle wrap hard to say without specs.

TwoBallScrewBall · February 18, 2019

It's blatantly obvious that the angle from trans to shaft is not the same as the angle from shaft to pinion. Much more angle in the rear joint. Just from eyeballing it, didn't put a gauge on it yet.

Just got back from ride, about to plug in USB stick and check video. Going to be towing with this thing in the spring so want to get this worked out.

Edited February 18, 2019 by TwoBallScrewBall

TwoBallScrewBall · February 18, 2019

Watched video, nothing obvious. Definitely cool to watch the driveshaft and suspension work while driving. Uploading now, I'll share the link in case someone else sees anything I don't once it completes. There is a good 2-gear WOT pull at 4:30, then at 4:55 I merge onto the highway from about 45mph to 80. There was heavy vibration felt in the truck on this 4:55 pull, but I am not seeing much on the video. Definitely coming from the rear, or at least it feels that way. All in the seat, nothing in the steering wheel or pedals.

TwoBallScrewBall · February 18, 2019

TRKLGND · February 18, 2019

1 hour ago, TwoBallScrewBall said:

It's blatantly obvious that the angle from trans to shaft is not the same as the angle from shaft to pinion. Much more angle in the rear joint. Just from eyeballing it, didn't put a gauge on it yet.

Just got back from ride, about to plug in USB stick and check video. Going to be towing with this thing in the spring so want to get this worked out.

Drop it back to the stock height and you won't have to worry about it any more.

TwoBallScrewBall · February 18, 2019

I swapped in the angled blocks I had. 2 Degree I think. Installed so the pinion points more toward the truck, not the ground. Vibration is still there at higher speeds under acceleration, 65-80mph. Might not as bad as with the flat blocks but I'm not sure.

I am going to clamp the front of the leafs, I read that helps sometimes. Makes sense, as clamping just the front of the leaf will make it stiffer, as well as give just a bit more upward pinion angle.

Edited February 20, 2019 by TwoBallScrewBall

TwoBallScrewBall · February 18, 2019

3 hours ago, paracutin said:

Drop it back to the stock height and you won't have to worry about it any more.

Where is the adventure in that???? I'm not ready to be boring just yet. Although I HAVE been told I have old man lights on my truck....

EDIT - excuse me - the wife's truck.

Edited February 18, 2019 by TwoBallScrewBall

midwestdenaliguy · February 18, 2019

Rough Country makes traction bars for $400 that have good reviews. That's if you have axle wrap occurring though.

TRKLGND · February 19, 2019

12 hours ago, TwoBallScrewBall said:

Where is the adventure in that???? I'm not ready to be boring just yet. Although I HAVE been told I have old man lights on my truck....

EDIT - excuse me - the wife's truck.

Shouldn't be any "adventure" in setting up a vehicle for towing. Be safe and boring.

TwoBallScrewBall · February 19, 2019

Clamped the front of the overload springs today. I like the ride better, a bit stiffer but nothing crazy. But no change in the vibration with the clamps, I still have a strong vibration, only under high power and only above 65mph or so. Truck is smooth at any speed at cruise, and smooth under accel until about 65mph, at which time I get a strong vibration, feels like from the rear, until I lift off the gas. Vibration is persistent from 65-85, did not go any faster than that.

Next step is to put the stock blocks back in the rear and remove the clamps, and see if I still have the vibration. If so, I might let the dealer take a look at it. If not, then I need to decide where to go from here since I have a 3" level in the front, so I can't leave the rear stock, as it would sit too low. Can we use lift shackles on a 2018 instead of blocks? Wondering if some of the problem is the additional distance between the spring and the axle with the larger blocks, allowing vibration to amplify or resonate / providing more axle leverage on the spring.