Cody Brooks

iTrader: (2)

I've read a bunch of threads about people having problems with shakes and vibrations at highway speeds that people can't figure out. I thought I would type what mine is doing and what I believe to be the problem for the sake of possibly helping others with such problems if all goes as planned.

Vehicle Info. 1999 chevy longbed regular cab with factory steel wheels brand new toyo open country h/t tires. checked out entire front end as far as all bushings go and tie rods ball joints etc. all are perfect. check U-joints perfectly fine. checked brakes and again nothing found. please note I'm ASE Master certified so I did every trick I could think of to find any slack or problem no matter how small it seemed.

The Problem. From about 55-70 mph worse around 63 than anywhere else feels like a tire vibration but it is intermittent. at first it is not too bad then it gradually gets worse then it starts to go away. lasts about 15-25 miles does it once every 50-200 miles. when the vibration is at its worst the truck feels like the brakes are on because it slows down quickly causing the cruise control to kick into passing gear to pull back up to speed. once it upshifts and goes back to overdrive it starts to slow down immediatly like the brakes are on and the cycle starts over again. so I end up turning the cruise off slowing down, pulling over, stopping and then starting over which often stops the vibration all together. very strange.

The Believed Fix. Got to looking at the Tech Service Bulletins found one for lateral vibration the fix that is recommended is new wheel hubs, leaf spring shackles (I think the shackle bushings are all that is really needed) and leaf spring bushings (which may explain why sometimes when coming to a stop I hear a loud clunk like the bed is loose). I found a member that had a pair of hubs for sale and found a bushing kit from energy suspension that includes shackle bushings and all leaf spring bushings as well as others for $80 shipped.

when everything gets in (should arrive during the week) I will install ASAP and tell of results then.

Anyone else ever had this problem or similar? maybe this will help those that are fighting a similar problem and have replaced drivelines and rebalanced tires several times or replaced them to no avail and are grasping at straws at what it could be.

05GMCL33

iTrader: (2)

This does sound like a very odd vibration, but just a thought are any of your wheels bent or out of round? I worked at a Goodyear shop for a few years and have seen bent wheels cause weird vibrations even if the wheel and tire balanced out very good.

Cody Brooks

iTrader: (2)

I watched the wheels spin while on the tire balancer to see if there appeared to be any wobble in them and did not see any at all. I honestly thought I had a tire with a bad belt that would sometimes move and create the vibration but the new tires didn't change a thing. The thing that puzzles me most is the way when it vibrates it slows then truck down so much it forces the truck to stay in 3rd in order to maintain 65mph otherwise it'll go back and forth between 3rd and 4th. the only thing I've heard so far that fits is the hub theory because if the hub was to create excessive runout it could create the vibration, and cause the brake rotor to drag on the brake pads. there is no vibration when I hit the brakes normally so i know the rotor is not warped checked the brakes to make sure they are not dragging.

TexCrew

have you tried rebalancing the wheels. it sounds similar to something wifeys tahoe was doing. we had the wheels balanced problem fixed. rides like a cadillac now.

05GMCL33

iTrader: (2)

The the hub theory does make sense, unfortunately this sounds like the kind of problem where you have to keep trying different parts to see if the proplem is resolved.

Cody Brooks

iTrader: (2)

rebalanced the tires that came on it. they where difficult to get balanced took alot of weight on a couple of tires. replaced the tires and still does it.

eallanboggs

iTrader: (1)

If the hub(did you mean rear since you mentioned hub in the same sentence as your leaf springs) had excessive runout this problem would have shown itself back in 99 not in 07. I'd change the bushings and take a closer look at the tires before replacing the hubs especially if you have had your 99 for 8 years as I have.

Tootall

iTrader: (79)

for the vibration, have you greased the slip yoke? That's where your clunk come from when coming to a stop, it might also be there on take off.

for the 3-4 shifting on the freeway, . . . it might be your torque converter. How many miles on it? Has the trans been flushed or had a trans filter changed?

budhayes3

iTrader: (19)

My truck used to do the same exact thing...vibration between about 55-68 mph. It happened with 2 different sets of tires, both roadforce balanced. After I lowered the truck by removing the rear lift blocks, installing Belltech 2" drop shackles, and Belltech lowering keys, the vibration is now gone My hypothesis is that it had something to do with changing the pinion angle after lowering the rear, or possibly compensating for a driveshaft balance issue by lowering the truck.

sbw9056

iTrader: (9)

Are you sure it's in the drivetrain? I once saw a fan clutch that was going out that caused a vibration like a drivetrain problem. It felt like you were driving with the parking brake on.