rear vibriation/ ujoints ?
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More Turbo
Joined: Feb 2004
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From: Spring Hill, TN
rear vibriation/ ujoints ?
My 78 F-150 4x4 has recently developed a vibriation in the rear end. I've had it for a little over two years and it always had a slight vibriation between 45-50 mph . But now it's staying after you reach 45 mph. When I let off the gas (coasting) it goes away. The last owner told me the u joints where pretty new and I have driven it about 5000 miles since then. The truck does have a 4" lift on it. Should I replace the ujoints in drive shaft or should I be looking some where else ? Thanks for your help.
Laughing Gas
Joined: Mar 2006
Posts: 1,164
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From: Tri-Cities, TN
Check all the u-joint nuts, as some could have backed off if they were not torqued properly. Bearings in the rear end could be worn also. Usually u-joints will produce a "clunk" when letting on or off the gas when they are getting worn, doesn't sound like your problem.
Postmaster
Joined: Nov 2003
Posts: 4,392
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From: Cab of a truck
Check out your rear driveline too. I thought I had a bad u-joint 2 days ago, I had a vibration but I didnt have the 'clunk' which usually goes along with it. And then this happened https://www.ford-trucks.com/user_gal...127001.520.390
Senior User
Joined: Oct 2005
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I just went thru this on my '79 F350 4x4. It always had a vibration around 50-60mph. One Saturday it got louder and actually turned into a "clunk" sound at lower speeds. U-joints were fine, so I pulled the shaft...yolk itself had a little play in it. I took it to a machine shop and had the whole driveshaft rebuilt. Put it back together....same noise. Pulled the cover off the rear end and found the problem, A bunch of metal chunks, and teeth missing on the ring gear! Luckily a buddy had a Dana 60 with the same gear. I bought the whole works from him and swapped out the entire rear end. Feels like a new truck now. I had got so used to the noise and vibration over time! Long story, but I would check u-joints first, if they seem good, pull the cover off the rear end......and keep your fingers crossed! Good luck, Mike
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Post Fiend
Joined: Jul 2003
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From: Spokane, WA
Two more things to check, if all else fails: Since the truck has been lifted it's possible that the u-joint angles are not matched which will create a vibration sometimes. Ideally the angle of the joint at the axle should be the same as the joint at the t-case. So take a look and if the angles are way off that could contribute to your problems.
The second thing is check to see that your u-joints are not out of phase. This can happen if the slip yoke has ever been pulled apart while the shaft was removed. The caps on both u-joints should be pointing in the same direction, i.e. if you layed the shaft on the ground and had 1 u-joint straight up and down the other one should be straight up and down as well. If they're not matched up then you will get a vibration from it. You can correct this by simply pulling the slip end of the shaft off and turning it so they're lined up and then slide it back together.
Don't know for sure if either of these are affecting you but it's worth checking into. You should be able to just look under the truck and inspect for both of these conditions.
The second thing is check to see that your u-joints are not out of phase. This can happen if the slip yoke has ever been pulled apart while the shaft was removed. The caps on both u-joints should be pointing in the same direction, i.e. if you layed the shaft on the ground and had 1 u-joint straight up and down the other one should be straight up and down as well. If they're not matched up then you will get a vibration from it. You can correct this by simply pulling the slip end of the shaft off and turning it so they're lined up and then slide it back together.
Don't know for sure if either of these are affecting you but it's worth checking into. You should be able to just look under the truck and inspect for both of these conditions.
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Laughing Gas
Joined: Mar 2004
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From: Maple Ridge B.C. Canada
good call ivan,i had the same problem many years ago.i had pulled the slip yolk apart and not realized it had to be aligned when i re-installed it in the truck.i too had a vibration.after i was told how to fix the mistake i had made,the vibration disappeared.i have noticed a lot of guys(like myself)have made the same error while servicing the drive shafts.-billy
Senior User
Joined: Oct 2005
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I have a slight driveline vibration on my '79 F150 (6"lift). Its due to the rear pinion angle. Been like that for years, never had to replace as much as a u-joint on it. Thats what I thought the vibration was in my F350 'till it got louder and started to "clunk"!! Good call.....if its getting louder, something is wrong somewhere! Mike
Post Fiend
Joined: Jul 2003
Posts: 11,945
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From: Spokane, WA
Originally Posted by hotroddually
i had pulled the slip yolk apart and not realized it had to be aligned when i re-installed it in the truck.
Junior User
Joined: Jul 2006
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The second thing is check to see that your u-joints are not out of phase. This can happen if the slip yoke has ever been pulled apart while the shaft was removed. The caps on both u-joints should be pointing in the same direction, i.e. if you layed the shaft on the ground and had 1 u-joint straight up and down the other one should be straight up and down as well. If they're not matched up then you will get a vibration from it. You can correct this by simply pulling the slip end of the shaft off and turning it so they're lined up and then slide it back together.
I thougth that the slip joint only went together one way. I think on my 79 350 it has one spline bigger that the others..
I thougth that the slip joint only went together one way. I think on my 79 350 it has one spline bigger that the others..
Post Fiend
Joined: Jul 2003
Posts: 11,945
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From: Spokane, WA
I've never seen a slip joint with one bigger spline personally. All that I'd worked with have the same size splines all the way around and can be degreed in pretty much any position which is why you have to be careful about misalignment.
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