Shaking/vibrating at speed
 

OK so my truck has a shake at a specific speed and it's driving me insane. I got a new set of tires, Falken ATs and found out one of my wheels was bent. Got a new set of wheels and it was still there. Upon closer inspection of the tires, found one was slightly out of round. Replaced it and the new one rolls true. Vibration is still there. Ball joints have no slack, outer tie rods have been replaced, but there is still a little slack in the inner tie rods. I'm at a loss as to what could possibly be causing this issue, it's driving me insane! Suggestions??

What speed? Speed specific?RPM specific?

This. Also what yr? Hyrdo or electric steering?

Driveshaft center bearing would be my first guess but it can be other things too like diff bearings or poor contact pattern. Front strut mounts. Poor road force on the tires (new ones can have a problem too) sticking caliper and on and on

It's a 99 Sierra rcsb. Starts at about 65, gets worst at 70. It's a vibration that matches wheel speed, not a high rpm vibration like a driveshaft. It's got a reg power brake booster, no hydroboost.

Does it seem like front end or rear? Speed related includes the driveshaft. The faster the car is moving, the faster it rotates. If the problem isn’t obvious, use a GoPro or borrow/rent a chassis ear from a friend or shop. Center support bearing on the driveshaft is a common cause of freeway speed vibration.

Oh, it's an actual truck lol. Ujoints would be my first guess. But again it can be a lot of things. You can remove the drive shaft and check the ujoints.

Is it vibration in the steering wheel or the truck itself?

I don't feel it in the steering wheel. Like I did it's not a high speed vibration like a driveshaft out of whack. It's wheel speed related. I just can't figure out what the hell it is if all 4 wheels are new and the tires are all good and balanced properly.

Wheel bearing? Carrier bearing?

You seem to be confused about how the driveshaft spins. The driveshaft is directly related to the speed of the vehicle just like the wheels. Rpm wil make no difference if there's a problem with the driveshaft or ujoints. Not in the wheel and shakes in the truck it's highly likely ujoints

Yea, I agree with Greenhornet. A bad driveshaft or driveshaft components can really shake things up. Literally.

Yes I know what that feels like, that's turning much faster than the wheels are. That's a high rpm vibration and I am familiar with that. I wonder if the rear spring bushings are the culprit.....

Do you have access to a lift? Get the truck in the air and give it shakedown.