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Very Frustrated...

mud hungry

mud hungry

1/2 ton status
Joined
Oct 4, 2004
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Location
Haydenville, Massachusetts
Hey guys, looking for help. I have a 97 Silverado 4x4 w/350 4l60E tranny. I have this vibration that is happening starting at around 30 MPH and continues up. I have had the tires changed rotated and balanced, and alignment done. I have checked all u-joints and wheels bearings. All tight. Oringinally there was some wear on the Harmonic balancer so that was replaced. Next I was told by a mechanic that the fan clutch was going so that was replaced. Still i have this vibration. I am getting pissed. The vibration is more prominant with the accerlarator on but I can feel it faintly with no gas. Also every once when I put it in reverse there is this clinking sound like the driveshaft rotating into position. Lastly the tranny was rebuilt about 50k again. Any guess. Any would be helpful. Thanks.
 
where do you feel the vibration? steering wheel? pedals? seat (aka the whole truck). Do you hear it more than feel it?

could be body mounts rusted through. may have lost the weight off your driveshaft throwing it out of balance. Quick check would be to take the rear driveshaft out, and drive the truck around the block on the front driveshaft in 4 wheel hi. if the vibration is gone, its most likely the driveshaft.

I also would lean towards the U joints, but you said you already checked those.
 
Haven't checked the body mounts but there isn't all that much rust underneath the truck. Surprisingly. the feel is in the pedal. and floorboards. the steering is stable.
 
It could be your pinion bearing too.

Or, maybe the tranny or motor mounts are worn out or loose.
 
It could be the trans failing, it could be in the rear end.

Set the e-brake, put the trans in neutral and see if there is any play in the pinion yoke (in/out or side/side).
 
yup, definatly sounds like its the drivetrain and not the tires. Im going with an out of balance driveshaft as my suggestion. Has any work been done lately that would cause the driveshaft to be disconnected? the caps on the u-joints can slide out laterally, but still lock down the driveshaft so its "tight" lengthwise. but allow the transmission lateral motion, which translates to an off center rotation, and significant vibration. losening the u-joint straps and pressing on the u-joint caps to recenter them fixes this.

also if you whacked the driveshaft and somehow managed to bend it, same thing, or as stated, if the weight came off, it would throw it out of balance.

with something as big as the driveshaft, spinning as fast as it is, it dosnt take much to get a very noticeable vibration. and as you stated you would feel it through the floor and pedals.

I know you said you already checked them, but this sounds very very much like my truck did right before the rear driveshaft u-joint exploded and the driveshaft fell down from the transmission like an..... well say excited stallion.

Again, i suggest driving around on the front driveshaft. even if you dont remove the rear, you should notice a decrease in the vibration, as less load is on the rear driveshaft. but to be sure i would remove it and drive around on the front axle.
 
Again, i suggest driving around on the front driveshaft. even if you dont remove the rear, you should notice a decrease in the vibration, as less load is on the rear driveshaft. but to be sure i would remove it and drive around on the front axle.[/quote]

This is going to be my next step. I will be picking up some u-joints tomorrow and while ready to change them take it out for a spin without the rear driveshaft. I will let ya guys know in a couple of days.
 
The u-joints can be tight, but have "flat spots" in them. Remove the rear shaft and move the joints back and forth to see if any have spots that are not as easy to move if that makes sense.
 
gone huntin said:
The u-joints can be tight, but have "flat spots" in them. Remove the rear shaft and move the joints back and forth to see if any have spots that are not as easy to move if that makes sense.
Click to expand...

So I finally had a chance to pull the rear drive shaft out today. Now there was NO movement while on the diff. However as soon as I unbolted it from the diff both caps when unstrapped FELL off. one had a chip in it as well as NO needle bearings while the second one was cracked. So finally culprit was in fact u-joints
 
at least you caught it early. my u-joint went out on my way to work. I had to drive it around on the front axle with the rear driveshaft hanging from the rear axle. for a half mile, slamming against the bottom of the truck as it spun till i could pull over and take it off.

glad you got it sorted out.
 
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