Just spitballing, remove driveshafts (one at a time). Lock the center diff and drive around.

 

I like hrhoward's answer better than mine. No cost to removing drive shafts.

 

I fought a vibration for quite some time and found that these trucks don't like tires inflated over 32 PSI. I put on larger tires and increased the pressure to 44 PSI and it vibrated all over the place. Dropped air pressure to 32 and it went away. Worth a try anyhow..

 

Hi everyone,

I changed out the front tires which were both wearing on the inside. The ride improved significantly and even the steering was smoother. I also ended up changing the alternator which eliminated the in-and-out vibrational noise completely. I’m guessing the bearings on the alternator were starting to go bad and it only became significantly noticeable at highway speeds.

However, while the truck runs great up to 80 mph, right at about 80 a heavy vibration comes in not related to acceleration that is constant and independent of steering. The back tires are in very good shape, I guess maybe I could check the balance on them? Any other ideas?

 

What tire pressure are you running?
Same pressure on all four corners or different in the front vs rear?

 

After the new tires were put on I did verify tire pressure. All tires were set per the tire type and the instructions listed on the driver’s door. I believe the fronts are 36 and rear are 38. It’s a pretty significant vibration though that doesn’t really seem to grow progressively, rather it just kind of starts at 80 mph.

 

Your fronts can go a bit lower for less vibration. Try it for a few days.

 

Found my tires run best at 32, anything higher and I get a vibration between 60 and 70 mph (larger tires)

 

Same for me
My tires are 235/85/16

 

Ah I see, I can definitely do that. Ya’ll don’t think lower the pressure is masking another mechanical problem do you?