check your drive shaft for balance.

 

no slip yoke to grease single driveline no carrier bearing so the only slip yoke is in the tranny and it gets plenty of tranny fluid. I'm talking about the front hubs accually and I bought the truck about a month ago with 74000 miles for a low price now I see why it was cheap but it doesn't matter I'm sure I'll have it fixed as soon as the new hubs arrive. remember this is info I got from a GM Tech Service Bulletin saying that if the truck was built before jan 1999 to replace the front hubs and if built before aprill 99 to replace shackles and bushings as well, my truck is one of the first 99's built. the thunk is most likely the shackle bushings in the rear. not a driveshaft balance issue totally different feel all together. when you take gm vibration school they teach the difference in frequency in vibration to tell what the cause is. the groups are 1. engine speed 2. driveline speed 3. wheel speed. this vibration is wheel speed. I know I've read alot of post by people that have had problems with vibrations on these model trucks and many never found a fix for it. I believe many of them could have been fixed with hubs or bushings. most of the people that have had vibration problems have balance and rebalanced tires then replaced tires and u-joints followed be drivelines and so on and so forth.

I got it to do it again today and played with it so what other diagnostic info I could out of it this time before it quit. It does for shure have a hub causing the vibration while making wide sweeping turns at 60 since I was by myself on a 4 lane at midnight with no traffic, I found that when the wheel is turned left a considerable amount the vibration stops all together which indicates front drivers side wheel bearing. As for slowing down on its own as if the brakes are on and downshift to try to maintain speed I pulled over after the vibration started to stop the front drivers side rotor was glowing red. the other brakes where warm as well but not as much as that one. I don't have any idea why it doesn't pull if that one is the only one dragging or dragging the worse but I have confirmed my earlier thoughts with that today.

 

Cody Could you post that TSB number? thanks

 

Sounds like you are on a good path and I see how the hub loose could cause the brakes to grab but what about a sticking caliper or rubber break hose coming apart and causing enough drag on the rotor to after time and heat of driving the drag increases and causing a shimmy as well? Just brainstorming here.

 

The 99-07 body style trucks had a chassis resonance problem in the front end for the first year, 1999. Some 2000's may have had this issue too, I do not remember extrly when the fix came out. Later years incorporated diagonal braces to stop the resonance. Take a look under a newer one and compare it to yours, you'll see.

 

subscribing

 

not a caliper or hose that is one of the first things I checking when I noticed it felt like a brake was dragging. I'm afraid I don't have that TSB number available but will be happy to answer any questions you have about it.

 

ok to update to today. hubs came in installed them. the old ones sounded and felt somewhat rough when I had them removed from the truck, however, with the tire and brakes in place you couldn't tell due to normal brake drag and the like. I'll update with more info as to whether or not the problem is fixed here in a week or so.

 

This does not have much to do with your vibration problem but greasing your slip yoke is a good idea, I had a bad clunk noise and then pulled my (single driveline) driveshaft out of the transmission and greased the hell out of the splines. After that the clunk was gone and slow moving from a dead stop was much smoother.

 

Had same problem. Went unrepaired because no dealer shop, Goodyear, or any other tire place could figure it out. Since i got my lift, there has been no vibrations whatsoever.