Truck front end bouncing after leveling

I'm not clear on which part is turned. Can you identify it by the color of the arrows? This photo shows the front strut's upper mount at the top, the front strut in the middle, and the rear shock absorber on the bottom.

That shouldn't matter. The strut itself is a round shaft inside a round cylinder, and can be installed any way. It's the welded-on mounting brackets that dictate it can only be bolted on two ways. The only thing that will change is the "spring plate". That's the part with the green arrow. The coil spring has to be indexed to that plate, as it will only sit on it one way, then the upper end of the spring fits in a matching groove in the under-side of the upper mount. At that point, if necessary, the upper mount has to be rotated 180 degrees so its mounting bolts line up with the holes in the body. The two yellow arrows are pointing to the two parts of the mount where the rotation takes place. That rotation is also what takes place when you you steer the truck.

When you buy new struts as a complete assembly with the new spring already installed, you have a fifty percent chance of having it oriented one way when you take it out of the box, and a fifty percent chance it's the other way. It doesn't matter which way it's installed on the vehicle.

For your bouncing problem, the first thing to consider is if the tires are larger than the original ones. That will put more road force on the steering and suspension systems. If the truck was raised up beyond the published legal ride height, that drastically changes the geometric relationship of the suspension parts. That can make them susceptible to road shock, and can degrade handling. In severe cases, it can make for a very tiring vehicle to drive. That bouncing will be felt in the steering wheel.

Another problem that can result is the driveshaft angle increases when trucks are lifted. That usually does not result in universal joints binding, but it can set up an irritating vibration at higher speeds. That will be felt in the seat and floor.

I can't really tell by the photo, but keep in mind, any vibration or bouncing has to be caused by something that is rotating. If it could be caused by something else, the problem would occur while the vehicle was standing still.

Now, to explain further, worn or improperly-installed steering and suspension parts can allow a vibration to be worse, or they can allow the bouncing to occur, but they can't cause it on their own. First there would have to be a problem with a broken tire belt, a tight front outer universal joint or CV joint that binds, then lets go as it rotates, or even a warped brake rotor. All of those things can cause a vibration that is too small to feel, but they can be amplified to the point you can feel them if the strut isn't doing its job, or if there's wear in control arm bushings, tie rod ends, or ball joints. Also, there doesn't have to be a defect with a tire. Road forces are transferred to the steering and suspension parts, so a good tire that's rotating normally can result in a vibration if other parts are worn or loose.

At this point I think I'd be looking for a second opinion for someone at a tire and alignment specialty shop. That's what I did for many years. Those people are experts at finding the causes of vibrations, noises, and bad tire wear.

Also be aware of the importance of the geometric relationship of the steering and suspension parts. This is greatly affected by altering ride height, which is the only other variable since this problem started. Imagine standing on one foot, with your arms at your side, and holding a five-pound pail of nails in one hand. How long could you do that before you got tired? Now imagine holding that pail with your arm stretched out to your side so it's parallel to the ground. You'd have much less control over that pail, and the much higher force would make you tired much sooner. This is what happens when the geometric design changes between suspension parts when ride height changes from what was designed in. Since I can't see your truck, this is why I would value a second opinion from a different shop. If there's a problem with the strut, the mechanic who did the work should fix it for you. The second mechanic may find some other cause that has been overlooked up to this point.