The vibration or "hop" thread ... again

mitchntx · August 14, 2004

I resonant vibration or "hop" or :shudder" or whatever you might call it ahs been discussed hear on several occasions.

I'm still chasing mine ...

But, I've made a few observations ...

When I put a couple hundred pounds on the bed, it seems to significantly reduce it.

So, I looked at the rear springs. I have about 1/4" gap between my bottom most spring and the rest of the spring pack. I had a friend jump up on the hitch and bounce the truck. It took about an 1" or 1.5" ove movement at the bumper to get the helper spring to "engage" the rest of the spring pack.

Theory ... the truck, unloaded, is riding on that single spring. When, some sort of irregularity comes along (road surface, tire out of balance, tire out of round, anything) the suspension is bouncing from the single spring off of the spring pack.

And because it's such a short travel, the shock doesn't dampen it.

To test the theory, I dropped the air pressure in my tires to 32psi. Unloaded, the "hop" was still there, but not as bad.

Theory ... the tire is absorbing more of the irregularities.

So, what do you folks think of these theories?

01silverado2500 · August 14, 2004

Could be, I know I get a vibration when I start off in rev or drive sometimes. I thought it could be tires slipping some? I just hope it isnt anything in the driveline, cause my transfer case was replaced last year due to an oil pump failure....I hope the tc didnt screw anything else up in the process.

Hutch · August 18, 2004

You have just described my truck to a "T"! I also have an '02 2500HD CC Shortbed with 8.1L/ Allison.

It seems to have gotten worse in the last few weeks. I let out some air in the rear tires and it seemed to help a little, also. However, I tow a large trailer quite often and just leave the tires around 65 pound all the time. I installed Rancho 9000 shocks and leave them on the softest setting.

I wonder it the springs need to be "re-arched".

Hutch