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j force
05-16-2001, 11:45 PM
i have a 84 chevy pick up with a 350 sb .it seems to idle fine but at about 2000 rpm's i get a wierd vibration ,,it mellows out as i give it gas ,any thoughts??/

85w/350
05-17-2001, 12:06 AM
What type of exhaust are you running off of this 350? I also have a 350 s.b. in my 85GMC and right about 1950-2000RPMs the muffler produces a perfect tone that makes everything inside rattle. I am running Flowmaster Muffler. I have also heard the same noise from a 84 Camero at 1900RPMs. Its a vibration that makes everything inside my cab rattle. I'm sure if you have a loud enough muffler it does this. Also at 55-60 it feels like my front end rattles. I am running 31 10.50 All Terrains and upon enquiring wierd rattle to a mechanice we figured out the lugnuts at that speed are expanding because any speed above or below that it doesnt happen. Same with the muffler a hair above or below 2000RPMs and it goes away. Hope this helps!

mstyles0927
05-17-2001, 10:09 AM
Also check the Ujoints at the front and back of the rear driveline. My rear Ujoint was wearing badly, and there was a bad vibration at medium RPMs. A new Ujoint took care of the vibration.

RTallday
05-20-2001, 06:36 PM
Now then, does it vibrate when you are not moving as well? If it does, then it is not a U-joint. If it always vibrates at around 2000 rpms, check out the harmonic balancer. If this is bad, loose or anything other then perfect, you will get a vibration. Let me know.

-Rich

75
05-21-2001, 05:45 PM
One other possibility that may or may not apply to your situation: If your driveshaft is a 2-piece unit, the centre support bearing and/or splines may be worn which could cause vibration.

Power mad
05-23-2001, 12:15 AM
The center support bearing was realy bad in my 81 burb.
After replacing it the vibration was worse than ever.
I put it up on jack stands and had a buddy run it slowly to 55mph.
The shaft looked like a jump rope. :(
$35 to have the rear shaft balanced and $15 to straighten.
See ya