I need help ?
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New User
Joined: Dec 2008
Posts: 2
Likes: 0
I need help ?
Basically i have a 79 f150 4x4 with fresh engine,transmission and transfer case. I just recently replaced u joints in front and rear drive shafts and im getting a very bad vibration between 40 and 45 mph. My local mechanic sez its in the drive shaft,u-joints or pinion. Help
Post Fiend
Joined: Jul 2006
Posts: 6,948
Likes: 44
Welcome to the site.
It would appear that you may have installed the slip joint(s) in the wrong orientation. It is important that the shafts u-joints are aligned. This is called the "Phase". If you have your shaft out of phase, it will vibrate. Having the shaft back in phase will solve your problems.
You might only be off as little as one spline, and this is enough to cause the vibration.
Here is some good reading.
Again welcome!
http://jniolon.clubfte.com/driveline...nephasing.html
Laughing Gas
Joined: Mar 2007
Posts: 754
Likes: 2
From: southwest Wisconsin
2nd on checking to make sure your drive shafts are in phase. Also make sure that the u-joints are properly seated where they bolt on to the pinion. I've seen one cocked off to the side a bit causing a vibration.
