Fighting a vibration

danb303 · June 11, 2019

2005 Reg Cab 4x4

I have a vibration that is driving me crazy. it vibrates a little at 25 mph then smooths out. At 60 to 65ish it vibrates pretty bad.

Not long after I got the truck I cranked the torsion bars up (I left about 1/4" threads) and bought wheels and new GY Duratracs. Shortly there after, I started noticing a vibration. I've had the tiers balanced 3 times and was still convinced it was the tires. last night I had a friend come over and I tried his tires. The vibration is still there.

I have:

turned the rotors and put on new pads

turned the drums and new shoes

pulled the rear driveshaft and checked the u-joints. They were smooth and still had grease in the caps.

the front wheel bearings feel nice and tight.

The truck only has 80k miles. I plan to pull the front driveshaft tonight and see if its a problem. Anyone else had a similar issue?

PTXer · June 11, 2019

I've had a similar problem just as you describe, but it comes and goes. When at 65, it goes away when I let off the gas and changes if the truck is "bouncing" from say a dip in the road. Seems like mine comes from the front end. I'm thinking U joints or differential. Haven't had the chance to really look at either.

danb303 · June 12, 2019

I removed both driveshafts (one at a time) and the vibration was still there. After a discussion with a long time now retired mechanic, he pointed out that the only two things that changed were the new tires and raising the torsion bars. I had already ruled out the tires by putting another set on the truck off a friends truck. He suggested lowering the torsion bars back to where they were just to try it. I thought he was crazy. I did lower them back down about half of what I raised them and *&#@ if the vibration wasn't greatly reduced. it probably reduced it by 2/3.

He thinks that the front axle CV's were worn at the lower ride height for 75k miles and now I have changed the angle on them and that could cause the vibration.

It also rides a ton better just lowering them 5 rounds. My shocks are worn out. I wonder how much of this can be related to the shocks?

PTXer · June 12, 2019

Great info. My shocks are worn too. The CV reasoning sounds very plausible.

danb303 · June 17, 2019

I have replaced the shocks and the vibration is still there.

I can't see a bent axle.

Anyone have any more ideas?

Interesting: If I drive it after it has been on my lift (two post lift so the suspension is flexed out) a while, it doesn't vibrate much at all for the first few miles. It stayed on the lift overnight and I drove it the next morning and I thought the vibration was gone. I'm not sure what that could mean.

Edited June 17, 2019 by danb303

sefiroxx · June 17, 2019

Vibrating in the steering wheel, rear end or whole truck?

Whole truck - drive shaft out of balance, bad u joint, engine tranny

Rear end - drive shaft, axle, shock, spring rate, bushing

Front end - steering, hub, balance, CV, tortion/spring rate.

Note, the spring rate, shock absorption rate are customized to vehicle weight and use. If you adjust one without adjusting something else you'll get weird results

danb303 · June 18, 2019

I feel it mostly in the seat. Just a little in the steering wheel.

I've ruled out the driveshafts and u-joints.

I serviced the rear differential and the transfer case last night. I haven't driven it so I don't know if it helped. I don't expect it to.

Drums and rotors have been turned. New pads and shoes.

New shocks.

I tried another set of tires and it still vibrated.

All the bearing feel tight

I've checked the axle the best i could with a straight edge.

I've been seeing this frame beaming???

When I lift the truck on my lift it seems to greatly reduce the vibration when I sit it back down. Especially if it stays on the lift for a few hours.