Bad Vibes
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Post Fiend
Joined: Nov 2001
Posts: 7,698
Likes: 4
From: Neenah, Wisconsin
Bad Vibes
I just finished installing my six inch skyjacker class two lift on my 95 f-150 supercab short bed truck. it now has a bad vibration at highway speeds. My assumption is that it is the front u-joint on the rear drive shaft causing the problems. i can't find a tranny drop crossmember and i'm hoping someone else whose run across the problem figured out a way to fix it. Any help would be greatly appriciated.
Ryan
95 F-150 supercab
Pictured with the 4", now rests ontop of a 6" lift.
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Ryan
95 F-150 supercab
Pictured with the 4", now rests ontop of a 6" lift.
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Elder User
Joined: Jun 1999
Posts: 861
Likes: 0
From: SE PA
Bad Vibes
I think this is bad angles on the shafts. The front, well you can't do much with that-steering takes priority. The rear however can be changed if needed. What you need for the angles on a shaft with only one u-joint at each end is equal but opposite angles, x-number of degrees down at the case should equal x-number of degrees up on the shaft at the rear. If you have a double joint at the 'case, then the rear shaft should be pointed directly from the rear to the 'case with no angle. The 'case is pretty much well set, the rear can be changed with the use of tappered shims placed between the spring and block or spring saddle. This is a common problem with lifts over 3-4". Might check the slip-joint if you have 'em, just to make sure you don't have side play in it. If you dinged the shaft, it could also be out of balance.
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Post Fiend
Joined: Nov 2001
Posts: 7,698
Likes: 4
From: Neenah, Wisconsin
Bad Vibes
The drive shafts not bent or dented anywhere,,,,i checked that when replacing the u-joints. The lift kit i installed had tapered shims attached to the springs in the rear and the blocks i installed to make up the additional 2 inchs are tapered as well. Do i install shims to offset this then. I'm not worried about the front as when its in four wheel drive it can shake all it wants. I'm mainly concerned with highway driving in 2 wheel drive. Thanks.
Ryan
Ryan
Senior User
Joined: Mar 2001
Posts: 181
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From: Annville PA USA
Bad Vibes
i really dont have anything to add about your problem.... sorry...
but i have the same truck, except mine has the purple middle.... with a 4" superlift susp, and a 2" body. I was thinking about "biggie-sizing" it, and going to the 6" superlift.... did you buy a whole new kit, or just pieces and parts (like new springs) etc. My bracketry has holes for both sizes, and didn't know what all needed to be done.
Thanks!!
Brian
but i have the same truck, except mine has the purple middle.... with a 4" superlift susp, and a 2" body. I was thinking about "biggie-sizing" it, and going to the 6" superlift.... did you buy a whole new kit, or just pieces and parts (like new springs) etc. My bracketry has holes for both sizes, and didn't know what all needed to be done.
Thanks!!
Brian
Elder User
Joined: Jun 1999
Posts: 861
Likes: 0
From: SE PA
Bad Vibes
Best way is to use a protractor to measure the actual angles at the 'case and the rear when sitting on level ground. If you have the double u-joint or cv at the 'case, then you can just use any straight edge along the shaft to the rear, always measure in the center of both shaft and yoke. If these angles are correct, then you will have to investigate other avenues such as shaft balance, suspension components like spring/shackle bushings, wheel bearings, ect. However, I think they do tend to point the rear up somewhat just to try to relieve u-joint angles somewhat with the idea being the little bit of vibs will be masked by the oversized tires?
Tuned
Joined: Apr 2000
Posts: 393
Likes: 3
From: Merrill
Bad Vibes
I had a pro-comp 6" lift on my 95'ford f-150 SC. I had to replace the U-joint's but didn't have any other problems except that I didn't lenthen the front drive line. and when the front end bottomed out it pulled the keeper on the back of the gear in the transfer case and wore out the case of the transfer case. So make sure that the front drive line has enough slip when the suspention is fully extended..
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Post Fiend
Joined: Nov 2001
Posts: 7,698
Likes: 4
From: Neenah, Wisconsin
Bad Vibes
Oddly enough i just got back from vacation with the truck. I drove almost 1000 miles, the first two hundred or so i got vibration, gradually it got better and the last 600 miles or so it was vibration free, i'm not sure what happened but oh well, its better now so i'm not going to worry about it anymore.
when i switched to the 6" lift all i had to buy new was the front springs and the front shocks and some blocks for the rear. The first kit had brackets predrilled for either 4 or 6 inch lifts.
Thanks for the ideas anyhow.
Ryan
when i switched to the 6" lift all i had to buy new was the front springs and the front shocks and some blocks for the rear. The first kit had brackets predrilled for either 4 or 6 inch lifts.
Thanks for the ideas anyhow.
Ryan
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Elder User
Joined: Sep 2000
Posts: 936
Likes: 0
From: Bay area
Bad Vibes
sounds like you have a CV joint on the rear of your Tcase? or is your truck long enough to have a carrier bearing?
If the CV is there you may have exceed the highest angle of it. and it basically beat itself till it smoothed out. either way something is up with your drive shafts. Problems never "fix" themselvs. They only hide until you least expect it.
If the CV is there you may have exceed the highest angle of it. and it basically beat itself till it smoothed out. either way something is up with your drive shafts. Problems never "fix" themselvs. They only hide until you least expect it.
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Thread Starter
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Post Fiend
Joined: Nov 2001
Posts: 7,698
Likes: 4
From: Neenah, Wisconsin
Bad Vibes
No,,,i have a single u-joint on both ends of the driveshaft, no carrier in the middle either. It is kinda wierd that the vibration went away, but i've checked the u-joints, they are new, they have no movement, the driveshafts straight and i can't find anything loose or bent.
