New owner needing help!!!Please!!!

[deadsled88]

I bought a 94 5.7 4wd extended cab silverado about 6 months ago. Everytime i get on the interstate above 60 the whole truck vibrates. And about 70 it feels like the back end is shaking. Im just curious if anyone who has more knowledge than i do since this is the first truck i have ever bought vould help me out or tell me where would be a good place to start. I love the truck but Im afraid to drive it out of town. Thanks and sorry if this is already covered on here i just couldnt find it.

 

[Biggershaft96]

First thing i would do is make sure the tires are all good, make sure the rims arnt bent, have the wheels and tires rebalanced. After that make sure there isnt any play in the driveshaft, pinion bearing, and make sure the converter bolts are tight.

 

[sgtpoliteness]

All great advice. I'd add (kinda ties in with the driveshaft) is look at the u-joints. You're going to want to focus on things that are road speed dependent, like the previously mentioned wheels/tires.

 

[Breakdown]

X2 on the tires being balanced... I had a 90 that vibrated bad at 60-70 then would start smoothing out around 80... Was a tire that was just enough out of balance to vibrate at speed... If you have a broken belt inside the tire they can do the same thing.. Check your torque on your lug nuts as well.
On a similar note, had a friend with a 86 2500 that was a frame off restore, unloaded at 60 the truck had a constant vibration no matter what we did that got worse like yours... put some weight in the bed and it was smooth as silk riding.

 

[tinfoil_hat]

I will echo the advice about tires and this is something you should take very seriously. Look for a bulge or any odd wear patterns on the tires. I have had them fly apart on the freeway before and it is not fun, I assure you.

 

[Bob L]

And don't drive 80 mph till it gets fixed.

 

[deadsled88]

X2 on the tires being balanced... I had a 90 that vibrated bad at 60-70 then would start smoothing out around 80... Was a tire that was just enough out of balance to vibrate at speed... If you have a broken belt inside the tire they can do the same thing.. Check your torque on your lug nuts as well.
On a similar note, had a friend with a 86 2500 that was a frame off restore, unloaded at 60 the truck had a constant vibration no matter what we did that got worse like yours... put some weight in the bed and it was smooth as silk riding.

A few months ago i had to take the bed off to fix a rusted out brake line. Is it possible that the bed may not be bolted down good or something like that. I also had my wheels and tires off and was gonna trade them when i got the truck and one tire was worn more than all the rest but i couldnt remember which side it came off of. Thanks for all the replies by the way. I am going to have my wheels and tires checked tomorrow. I have to drive it on the interstate 20 miles every other day to go to physical therapy.

 

[deadsled88]

So i went and had my wheels and tires balanced tuesday and aparently the rears were chopped. Now ive only had this truck for a short time and only put about 3k on it. The tires that are on it still have over half tread on them. So i still have the vibration but now i the problem. It still vibrates amd the balance didnt help a while lot. But... my question is. What would cause the rears to be chopped and what are some things i can do to help the vibration as i dont have the money to replace the tires right now since i wasnt expecting to have to for a while.

 

[89RCLB]

An out of balance/bent drive shaft, bent axle or wheel and out of round tires can cause serious vibration issues. Chopped tires are typically a product of worn shocks, but not always.

If it were me I'd get an assistant, chock the front tires, get the rear of the truck up on jack stands, have your assistant start the truck and put it in gear and inspect for obvious signs of bent axles/wheels and out of round tires. Take a look at the driveshaft while the running gear is in motion as well. If all that checks out as "okay, I would then pull the driveshaft and take it to a shop that can check the balance and correct if necessary. As for the shocks how does the vehicle react to low spots in the road? Does it seem to bounce around a lot? Check out this write up on testing shocks: http://knowhow.napaonline.com/testing-your-shocks-how-much-bounce-is-too-much/

 

[tinfoil_hat]

Chopped as in cupped? Worn suspension, alignment? When you pulled the bed off, did you do do anything to the shocks or springs or even the axle itself?