Remove the rear wheels and inspect the brake rotors for mud in the vents or evidence of a balance weight being thrown out.
Rod, he said he replaced rear brakes and rotors.
thanks, I will check them again to be sure
Maybe you need to revisit the U-joints. Last fall I put a pair of U-joints in my daughter’s Mustang and off she headed home; about 70 miles away. She called later and said there was still a vibration; just not as bad. So off I go on a road trip…
With the shaft back out I noted a little bit of side play in the joints so I ran the shaft over to a driveline shop. The guy at the counter took one look and said “O’Reillys joints?”. Yep.
He said they’ve seen dozens of faulty joints from them.
So they took it to the back, installed a couple of Spicers, and smooth as silk now.
Something to consider all depending.
When you replaced the U joints in the driveshaft…did you mark the relationship of how the shaft went together…they are balanced assemblies.
We had a guy on here who did his U-joints and had vibration problems…until he did them over again…this fixed it.
If you did your own u joints…I think the issue still lies there. You should easily be able to discern if its a brake hanging…or tire balance…if its neither of those… Revisit the U joints and driveshaft.
@“Honda Blackbird” mentioned, it is easy to get the yokes turned 180 degrees if you did not mark them when you did the U-Joint.
If you did your own you may want to pull it apart and turn the yoke 108 before you put it back together.
I did this once when my chalk mark got rubbed off as I worked. I pulled it apart and turned the yoke 180 and it was smooth again.
You probably checked on the pinion shaft to see if it was loose and might have too much whip going on. It’s probably OK if the seal isn’t leaking. I’ll bet the exhaust isn’t loose either but… Try driving with the tailgate down. I’m out of new ideas now.
So as far as my the driveshaft goes, Ford had put on a brand new one after the fact of dealing with the u-joints of original - and the new one did not make a difference. I then took the original to a balancing shop-who determined it was fine.
If the truck is jacked up and the axle supported on stands so that the drive shaft angle is correct the drive train can be tested by running the wheels up to speed to bring on the vibration and carefully watching to see or hear the source of the vibration. If the problem appears to be on a wheel remove the wheels and retest with lug nuts securely holding the rotors in place.
Any chance it could be due to bad bearings or a glitch with the ring and pinion gearset in the rear axle?
Have you checked to see if there is any up and down movement in the rear wheels or excessive sideplay?
yes, ive checked the bearings and movement within the wheels. doesn’t seem to be an issue. But not sure about how to diagnose the ring and pinion?
It seems tough to simulate the vibration when its is off the ground, tried several times to lift it up and even Ford did it several times with analyzer and couldn’t find it. Only seems to appear on road driving speed.
Since this occurred immediately after replacing the rear tires, it seems almost certain it would have to be something about the tires. Either the wheel weights are placed incorrectly, the lug nuts are doing their thing correctly, keeping the wheel where it should be on the hub, or the tires are out of round or wobbling left and right. Has your shop tried using a dial indicator gadget to check for out of round=ness or wobbling of the rear tires?
Edit: Just curious OP, what’s the configuration of your truck’s drive shaft? I have a Ford 4WD truck too, and mine, the driveshaft is a two piece unit, splined in between, with double u-joints on the differential end. A straight shot, no center-supporting bearing, between the transfer case and the rear axle.
Have you tried rotating the tires. Front to back and back to front.
If the vibration moves to the front, it has to be a tire or wheel.
Maybe you broke a belt in a rear tire and its vibrating? Like @“Rod Knox” mentioned…jack up the rear and run it with the wheels on…and then OFF…see whatchagots. PLEASE do this operation properly…the result of not doing this safely I think I saw on a 3 Stooges episode…haha
This procedure will rule out a lot of things real quick.
as mentioned in paragraph, I have changed out the tires several times and even purchased new ones from the set that originally brought the problem up. Ive rotated and balanced them many times with no difference.
it is a one-piece drive shaft with u joints at one end.
What if you installed – temporarily I mean – entirely different wheels, tires, and lug nuts all around? Maybe borrowed from another F150 that doesn’t have this problem. Might provide a clue anyway. It’s possible the wheels were somehow damaged when the tires were replaced the first time. Or the wheel lug nuts got mixed up with those from another vehicle.
Is this an automatic transmission? Just a wild and likely incorrect guess on my part but what about a torque converter issue.
Converter vibration often comes in around those speeds and Ford has had bulletins on it over the years.
My current and past Lincolns would at times develop a shudder around 45-55 MPH and it’s always been cured with a complete fluid change.
In some extreme cases a new converter may be needed.
I can always tell when the trans fluid needs to be changed. The car will start getting a very subtle shudder in it about 50 MPH and when the fluid hits about 40k miles or so. Ergo, I always do fluid changes about 30-35k miles.
The shudder is not apparent when revving the engine while the car is stationary.
Anyway, that’s a random and very wild guess at best but at this point…
@ok4450 stole the thought from my mind… Torque convertor lockup malfunction can cause the same sensation. This can be tested by running the vehicle up on stands…with and then without wheels… Also with the lockup solenoid either disabled or disconnected…and then connected again.
Even if it isnt that…it can simply be the Torque convertor internals that messed up…Not a too common occurence but I have diagnosed and repaired this condition prior…and it took me a long while to finally reach this conclusion. I was trying to rule out everything before “Going There” to the Convertor…bec honestly I didn’t want it to be the convertor for obvious reasons. In the end…that was it.
Another test you can do is to “power Brake” the vehicle… Foot on brake…foot on gas simultaneously…do you feel a vibe at that time? If there is a torque convertor fin problem it will be felt at that time…if nothing is felt…move on to the lockup solenoid. Your solenoid may be weakened and barely able to fully engage lockup…and its sort of vibrating like a tattoo needle…engaging and disengaging lockup rapidly… Id be looking into it…but thats me…