2000 silverado vibration between 40 and 65mph

Hello, I recently got a used 2000 silverado 1500 ext. cab with a short bed. Has a 5.3L engine. I noticed it has vibrations at highway speeds. I thought it was the crappy tires on it so I had all the tires replaced and balanced. Now it has all new tires and does the same thing. Runs really smooth all the way up to 40mph and then the vibrations begins. It is mostly felt in the steering/dash and pedals. A little more pronounced on accel. but vibrates if your on the gas on not. Once your reach 65mph, the vibrations stop. I have also noticed that asphalt makes it vibrates more. When I go over concrete overpasses in the problem area of 40 to 65mph it smooths out. I took a look under the truck and saw nothing obvious. U joints feel tight and no play, seen it had weights which apeared welded onto the one piece drive shaft. Any ideas what to check?

Thanks,
Jessie00721

Wheel bearings,hubs.

If you only feel this in the body or floor I would suggest removing the driveshaft for a closer look at the joints, also make sure the driveshaft is not bent or kinked,

with your vehicle I would look at the hubs and the front end steering components especially the tie rods.

when you greased the front end did you see broken grease seals? any joint play with one wheel on the ground and the other off and your working the wheel/hub when looking at these joints.

remove the tire and then remove the front wheel sensor from hub is the grease rust colored ?

if the hubs are bad do not buy any cheap chinese hubs. only get the timken hubs.

this is 4WD ?

If the steering wheel vibs this is not the drive shafts . I would still check them out however since this is a new vehicle to you.

you also should check all the drive train fluids and at least replace the transmission filter and fluid. with 4wd you will need to do much more fluid replacing.

My 1997 Chevy Silverado 5.7L did this too. It turned out to be the transmission which actually finally gave up on me about a week ago. You can either get it rebuilt now or let it go as far as it will. Mine always did it right before shifting into overdrive. Now it won't reverse or shift up so I'm driving around at 35mph hitting 2500RPM.

Thanks for all the responses so far. I did not get a chance to really look at it this weekend. I know the other day when I had the alignment done they did mention that I think the pitmen arm had a little play but would not effect alignment. I was pressed for time so I had nothing else done. Maybe that play is causing it? I really dont know yet. Still need to pick up a manual. The truck is 4wd and that is operational. I personally did not spin the tires or move them any to check any play or noise. I would think the repair shop would of gave it a once over to repair everything they could. I think the issue was on the passenger side. I have noticed that if I have someone sit on the passenger side, there is hardly any vibrations. Notice it more when it is just me driving. I will get out and check it as soon as the rain lets up. Thanks again for all the replies so far! I really appreciate it. The vibration is mostly at the steering wheel and at the higher speeds it is felt a little at the pedals but much more noticable at the steering wheel with just 1 person in the truck. Concrete much better then asphalt, below 40 is as smooth as can be and above 65. Thanks!

when the alignment shop [I hope not a tire store] stated that the idler arm had some play , then they still did the alignment this tells me they are a repair/alignment shop to avoid.

step one the alignment shop checks all front end components for wear/defects. any defects work stops .

It was pepboys, they said it would not effect alignment? idk

It was pepboys, they said it would not effect alignment? idk

That now shows that this shop should be avoided.

so you replace the worn idler arm . now they will align for free right ??