Hi all,

I'm tired of my Bronco shaking and need some help tracking it down. It shakes all the time, no matter the speed. I can see my engine lid vibrating and bouncing as I go down the road and I can't imagine the number it's doing on all my components.

I've rotated the tires, I have balance beads in the tires, I replaced a burned up u-joint. The tie rods seem tight (at least was told they were nice and solid last time I had it aligned). Alignment seems good.

What are some things I can do to diagnose? Things to look at?
I'm fed up with the vibration.

I can feel it at every speed from 5 - 80 mph. Clutch in or out. Accelerating, decelerating, coasting, it doesn't matter. It just shudders all the time.

 

Does it feel like it's coming from the front or back? While this isn't a complete list, here are a few other things to check:

Bent drive shaft, axle pivot bushings, radius arm bushings, 4wd spindle hub nut backing off, ball joints. How old are your tires and how bad are they worn? Cupping or other uneven tire wear can cause bad vibrations even if it's aligned.

 

Thanks for the ideas. It does feel like it's coming from the front, come to think of it. But that's more of an "instinctive" feeling, than a definite yes.

Not a bent drive shaft, as I probably would have known if I had done that.
Axle pivot bushings and radius arm bushings were replaced. Not recently, but they're not 35 years old.
Rebuilt the brakes this summer so the spindle nuts are freshly reset (shuddered before and after the whole rebuild).
Tires are only a few years old and look to be wearing really well, unless there's something wrong with them that I can't see. Nice even wear. I've tried rotating them before, but it didn't seem to do much.

The ball joints are about the only thing that hasn't had attention. I've kind of had my suspicions about them being the culprit (they have some play) but wanted to get unbiased opinions first.

 

Too bad you didn't do the ball joints when you had it tore down for the brakes this summer.... If they have a good bit of play I would take it all they way down. New Moog joints greasable ball joints and I would also replace all 3 u joints in the front axles etc.

When you replaced the radius arm bushings did you notice if the hole was wallowed out? I know badly worn bushings will cause that hole to get larger and even with new bushings will still cause some vibrations

 

Yeah, I wish I would have when I had it all apart, since that's about 80% of the work right there.

As for the radius arm bushings, it was about 8 - 10 years ago, so I don't recall. However, they look as fresh today as they did then.

 

Sounds like a rear driveline issue to me.
The fact that it does it all the time takes the front u joints out of play.
My first thought is a bad u joint in the rear shaft, did you take the shaft out for any reason at any time? If you did and did not phase the joints that would definitely cause what you are describing.

Post 10 shows how to check phasing in case you don't know:
https://www.ford-trucks.com/forums/1...l#post14236128

 

Hrm! Come to think of it, this vibration has been ever since I replaced the engine/transmission/transfer case.... I have no idea if I put the driveshaft in phase.

 

What is the correct positioning for driveshaft phase on a Bronco with the double cardan joint up front? Not sure how it differs from the illustration in the link with the single U-Joint.

Either way, I went out and looked at it, and the first thing I realized is that the seal on my rear axle is blown and there's fluid leaking. A vibration in the driveshaft would definitely cause that.

 

Here is a pic of a cardan drive line in phase, notice that all 3 joints are on the same plane on both sides. This is the key so they rotate on the same axis.
If they are not you get binding which translates to vibration and yes it will kill a pinion seal.

 

Just went out and looked. Looks like it's in phase. That would have been a nice easy fix.

 

Well it is one less thing on the list.
How much play do you have with the trans in gear trying to turn it by hand? Also back and forth or up and down movement? The pinion seal is bad, you may have a ring and pinion problem in the rear end.

 

x2..

a good way to tell is..does it do under power? does it go away slightly under float? this may be a better indication though when it first starts to vibrate

I just recently had a failure of the inner pinion bearing on one of my 9" rears..caught it in time to save the r/p

 

It's been shuddering for probably over a year, and the leaking pinion is since I was under there last (which was about two weeks ago to replace the u-joint).

The vibration seems to only ever change with speed.

I hope it's not the R/P. I don't want to deal with that. =/

 

The Rear Pinion makes a grinding noise when it's broken for a while, have you checked that the engine and transmission mounts are fine? are they properly tight?.

 

I use a "mag" fill plug and check it ever so often. if you see pieces instead of fuzz..hmmm

When mine failed if first began to shudder under power. It never went far enuf to cause the seal to leak. In a nine " there is a small nose bearing as well on the end of the pinion shaft.

It's too bad these 9" r/a's don't get the advantage of being drained and filled as often as they should prolly. It's such a pain to refill them even if you drain them. If you DO pull it out..I would consider the drain/fill plug mods..Hope it's not ur problem..