Pretty puzzled here. I have a pesky vibration in my '79 F 150. It starts the vibration at 45 to 49 m.p.h., diminishes and then starts again at about 65 and continues to get worse as speed increases. I feel it in the seat primarily and can feel some vibration on the transfer case **** though it is not severe at that point. The truck has a 6" lift, am running 35" rubber. I have had the tires and wheels balanced multiple times with weights and beads. I've swapped out tires and wheels. I've had the driveshaft totally rebuilt and balanced. The yokes are "clocked". I've had the rear differential rebuilt except for the ring and pinion and they look in great shape. I've had the rear axles checked out and rear bearings/seals replaced. The front hubs are free wheeling. Nothing I do seems to change the vibration. Has anyone else experienced this? Anybody have any suggestions as to what to check or do next? I guess I could live with it as long as I drive at lower speeds but would rather find and fix the issue. Also, the vibration sets up a deep sounding harmonic sound. The sound is not extremely loud but one can definitely hear it. Thanks.

 

Check the diff yoke. Mine would wipe out a ujoint in a week. Its very hard to tell but recheck your rear ujoint and if the bearings are dust then replace the yoke. I have seen this many times

 

Thanks. I'll double the check the rear U-joint and the rear diff yoke. Appreciate the suggestion.

 

Vibrations suck. Hope you find it

 

Have somebody drive alongside of you and see if they can see what is shaking.

New rear shocks may solve problem if The axle is hopping.

 

Secure your smartphone (video camera) pointing at the d/s or center support bearing or whatever, and take a spin down the road?

 

Hi,
You have a lift kit on it did your kit give you shims to adjust the pinion angle? plus is the truck standard cab cc cab or extended? i seen alot of issues with carrier bearing (drive line) can shutter as well. My guess would be pinion angle its pointed down to far neg degree good luck!

 

The truck was lifted when I bought it so I did not install the kit. The drive shaft is at a slight angle down from the yoke on the transfer case. The drive shaft is almost straight with the yoke at the differential. My mechanic says that some angle is not a problem. Does anyone disagree? I've considered the transfer case being the culprit but no one I've spoken to thinks that is a possibility. I like the idea suggested about securing a camera. I will try that and see if I can see something. Thanks again for all the suggestions. Lyle

 

There is your problem your pinion angle is straight when u accelerate ur pinion lifts up creating positive degree its needs to be pointed down technically ur angle needs to be minimum 1 degree down max of 4 degrees down. If u say its straight at t case u need to shim pinion down

 

One other thing u don't have a constant velocity (cv) drive line in the rear right? If no then point pinion down. I was a gear and drive line mech for close to 12yrs and have helped a lot of those type fixes not sayin I'm an expert but I seen a lot

 

I appreciate the information. Of all the research I have done and the inspections by a couple of pretty savvy guys here, it is looking more and more like the pinion angle, as you suggested, that may be my problem. We are now trying to figure out how we are going to fix it. If we git 'er done, I'll post for all. Thanks.

 

Good deal glad I could help. One other thing look at the axle and see if there are shims already there? If so they might be shimmed the wrong way so u might need to rotate them have a good one

 

did you ever figure out the problem. I have a similar situation just don't know exactly where to start. u joints were new a year ago and I haven't driven 1000 miles since then.

 

I have not definitively solved the issue. I talked with a retired Ford mechanic of over 49 years experience. He drove the truck and checked the driveline. There is some slack in the driveline even after rebuilding the differential. He said that very few guys know that the case that holds the spider gears gets worn and those gears become sloppy or wear out and cause a vibration. I checked with the guy who rebuilt my diff. and, sure enough, he had not replace the case for the spider gears. That is our next step. I'm waiting for him to call me and tell me to bring her in. I don't know what else it could be. If you are patient, I'll be sure and post the results as soon as I get these fixed. If the problem goes away, we will have solved the problem. No need for a bunch of us shooting in the dark. When I get it fixed, I'll list all the things I have done to this truck in solving this issue. Take care. Lyle

 

Oh boy. That doesn't sound like fun. Ive got some new wheels and the PO of my truck has a tendency to buy cheap tires so I may need to look into that first.