I have a 99 2wd extended cab short bed with the 5.3. I get a vibration that start around 75mph and progressivly gets worse untill the point where it feels like the driveshaft is coming throught the floor. Then whe nyou let of the gas it totally feels like it's comming apart until you get back down to about 65mph. I have the dual driveshaft setup with the carrier bearing. THe driveshafts have the dual carden u-joints. I have had the truck taken to a driveshaft speciallist the removed the driveshaft, replaced all the u-joints and carrier bearing and rebalenced it then intstalled it. This didn't fix the problem. truck is stock height so there is no extreme angles. you can feel a slight vibration from stop all the way up to around 55mph then it starts getting crazy. This truck used to be so pleasent to drive on the highway, now this shimmy makes it scary to take on road trips, as crusing speed of 70-80 feels like the truck is comming apart. I have narrowed it down to a bent trans tailshaft, driveshaft front input yoke, or possibly a rear end. Like I said the driveshaft shop when through it and rebuilt the whole thing($500 later still not fixed) Any one else with this problem? Any suggestions where to look?

 

Have you had the balance on the tires checked? There was a bulliten a while back for the NBS for a vibration and 2 piece driveshaft. It was replaced with a 1 piece shaft. Unfortunatly I think it was only for 2500 and up.

 

I have a 99 Silverado ECSB that also shimmies, but it's intermittent at pretty much all speeds. This problem has chewed up a set of tires(cupping). I have located a Technical Bulletin that claims to fix "Front End Vibration". Man I hope you have an extended warranty, because I don't and all I see is a big money pit. Check out TB #00-02-35-004 Date: June, 2000. Before you go and pay $25 for a years worth of TB's, let me give you a preview of what kind of F*@!#$g you're in for.
The following repairs are supposed to be completed all at the same time because "Incremental replacements will adversely affect the handling and ride qualities of the vehicle." OK I hope your sitting down:

1)The tires must be in accordance w/some corp. bulletin (I think it's changing the tire size to 255's from 235's - not sure but unimportant anyway).
2)The steering rack must be replaced with a revised rack.
3)The left front steering rack mounting point must be reinforced.
4)The lower control arms must be replaced w/units incorporating a revised bushing.
5)The power steering pump metering valve must be replaced w/revised fitting.
6)If vehicle was built before June 1999(I think it's june) then GM suggests replacing wheel bearings(replacing the hub).
7)Allign front suspension.

If you want or need more info (like the TB itself) then PM me. Hope this helps more than hurts.

 

WHat if it isn't his front end.

I have a feeling, his and mine is a lot alike.

My shake starts up at about 85 though, and by 100 it's getting pretty bad.

 

yeah, mine isn't eating tires and the front end stays aligned pretty well. It feels like it is right under me in the trans/driveshaft tunnel. My front end does click when leaving a parking stall or certian low speed menuviers when i am cycling throught the range of the front steering. It's sounds like I have some lower control arm bushings out when I go over really rough stuff like speed bumps and bad pot holes. So yes i agree with you i probably have some type of front end stuff that needs replacing but the orginal concern of this post was like the other member posted at around 80 and especially 100 the driveshaft feels like ti's coming throught the floor. If i run it up and let the top speed limiter catch it you better say two to three hail mary's cause something isn't go right under there.

 

Check your pinion bearing,and your pinion yoke nut either the bearing could be bad,or your nut may have worked it's way loose.

 

He just had all that replaced ....

Get under there and look at the drivesahft. Just make sure it's straight coming out of the tranny and going into the rear axle. Look for any other angles as well. When did this start?

 

Mine is the same way. I have had my driveline rebalanced and gone through a handfull of u-joints. I am afraid to travel more than 100 miles with it and on a trip from TX to WA it left me on the side of the road in Utah. I guess I noticed it most after the 2/4 drop, so I switched over to a 4/6 and it still vibrates.

 

Mine vibrates from about 85-92, stops and then starts up again at about 110 or so.....I've had the driveshaft re-balanced and the front end aligned

 

Mien didn't start until the 80e went in. That was after the new trans crossmember went in, so I'm thinking mine is still driveline related. I'm going to check welds and mounts and such to see if it could be that.