1 Ton Chev Vibration At 40 Mph

[John288]

Hello

I have a 2000(old body style) 1 ton Chev with a 10 foot dump box on it. It is a 350, automatic. The problem is a vibration starting at 40 Mph with a load and without in 2nd, 3rd, and 4th gear. I have done a neutral and park test to eliminate the engine, set it on jack stands with the wheels on and off, replaced ujoints, checked the center bearing and slip yoke, had the driveshaft balanced, checked the axles for bends, removed the diff cover to check for wear, checked rear wheels bearings for play, checked the torque converter bolts, and I took the tailshaft to a transmission shop and the guy said the bushing didn't have enough wear to be replaced. Any ideas?

 

Thank you

[redvett]

Have the tires balanced.

[John288]

Have the tires balanced.

 

Thanks for your reply

I have run it on jack stands with out the tires on and it still has the problem.

[superjim]

Is it 2wd or 4wd?

[John288]

Is it 2wd or 4wd?

It's a 2 wheel drive.

[John288]

Driveline specialist suggested tightening the pinion nut. This seem to lessen the vibration to a reasonable amount.