Vibration and Dragging

So I have recently acquired a 1990 BroncoII 2.9, 5speed, 4x4. About 90k miles. Last week I was driving it home from classes which is about 40-50 miles away. It started having a moderately loud vibration and rumble under acceleration from a stop, and then again around 45-55mph. I got it home and parked it.

This Saturday we trailered it to the shop to take a look at it, but didn't find anything obvious. One of the CV joint boots on the rear driveshaft was damaged however so we replaced it. Took it for a drive and everything seemed great.

We then put it back in the shop to try to convert the auto locking hubs over to manual so the 4x4 would work. The conversion went well, and my dad drove it around to make sure. At this point the rumble came back worse than before. My dad said he felt an extreme drag and says it sounded like a tire was grabbing/skidding. He took the cover off the rear end, checked for slop in the wheel bearings, and took the brake drums apart. We're stumped. We'd like to see if anyone has any ideas before we get too serious about tearing into it.

TL;DR:

Vibration, rumble and dragging. Replaced rear cv driveshaft, checked front bearings, semi-checked rear bearings, checked rear end. Fixed 4x4, still having rumble, vibration, and dragging.

When this occurs I assume it is in 2wd and front hubs unlocked. Is this correct?

I also assume that you aren't running in 4WD on dry pavement

Given those assumptions and the way it comes and goes...

Shaft phasing would be consistent so that rules that out.

A bad u-joint, if you put a u-joint verses a the original CV shaftt and it came from a salvage yard a possibility possibly, but dragging?

And bearings and diff look good?

This may seem like a non-sequiter, maybe a collapsed brake line? The internal lining of the rubber lines can break apart and either block the line completely not giving braking to that wheel or, what may be happening here, act like a check valve. When you apply brakes it acts fine, but when you release brakes the check-valve like action keeps pressure at that one wheel. If your rotor or drum isn't really round it will continue to cause some vibration and of course it is dragging. This could explain the intermittent nature.

Outward appearance of the rubber portion of the brake line often looks totally fine.

This happened on my left front wheel. It also pulled slightly in that case being it was in the front. As long as I was on short trips it never showed up but longer trips things got hot enough and it would start to vibrate. Sometimes hitting the brakes would make it go away and then next time it be back. One time it had gotten severe and vibrating so bad that the lug nuts had taken on a blue hue and scorched my finger when I touched one of them. In other instances, less extreme touching lug nut on that wheel was noticeably hotter than lug nuts on other wheels. The heat gets put into the rotor by the brake dragging.

There brake lines will collapse . . . any could, but these definitely do.

I had a problem that was about the same as yours when I first bought my Ranger. One of the front caliper bolts had backed out and was gone. It only made noise once in a while. I went over the whole truck before finding it. I would go through the whole brake system real well if I were you.

ab_slack, your assumptions were correct. As the replacement driveshaft is brand new, I think we can rule it out. We'll give the brakes and diff another once-over and see what we can find. Thanks guys.

If you have a brake dragging, the offending wheel should be hot to the touch. If its bad enough you should be able to smell the hot brake lining.

ab_slack, I missed your first questions. The hubs were in fact locked in, but the transfer case was not engaged. Sorry for any confusion.

Also like to note my dad says when he pushed the clutch in to coast to a stop, the truck stopped itself very quickly with a lot of drag. No foot on the brake.

Thanks again.

cheasfridge said:

ab_slack, I missed your first questions. The hubs were in fact locked in, but the transfer case was not engaged. Sorry for any confusion.

Click to expand...

Now that is a very different kettle of fish. A very important distinction.

With front hubs locked, even with transfer case not engaged, your entire front driveline is spinning which brings in a whole bunch more sources of vibration.

So you need to identify if it is the front driveline or not. Easiest way to determine that is unlock the hubs and see if the vibration and dragging occurs. If it still does it isn't related to the front driveline but could potentially still be front wheel issue (like collapsed brake line).

If the vibe and dragging goes away when you unlock the hubs then you are looking something in the front driveline. Good news is that if it is something there, you can drive 2WD with hubs unlocked without the vibe till you track it down.

In the front driveline you have 5 u-joints, the front differential and all the associated bearings in the transfer case, differential and spindles.

Did you do the front wheel bearings? If so, were the ones behind the spindle for the axle shaft done? Those only come into play when the hubs are locked.

The right hand axle shaft has two u-joints and a slip yoke between them. It is setup like a dirive shaft. There is no key on that slip yoke so if it been pulled apart the phasing could be messed up. Bad phasing will cause vibration but probably wouldn't explain drag.

The left axle shaft has just one u-joint so there isn't any phasing issue there. The difference between right and left is because the differential is mounted to the left traction beam arm so the u-joint just allows for steering. The right needs to response to suspension movement and steering.

Front drive shaft u-joints very definitely could be a problem.

The front drive shaft is fairly easy to get out and to change the u-joints. The left axle shaft and outer right axle shaft u-joint require pulling the spindles to get at and replace then (watch the right side phasing putting back together).

The inner right axle shaft is a bit of a pain. Since the stub shaft out of the diff is held in by a c-clip inside the diff, you can't pull it without opening the diff and since there is no diff cover plate, just the traction beam it means dropping the diff. I hear it is possible to change that u-joint in place. It is on my agenda to replace when the weather improves.

Anyways that is all speculative. Unlock the hubs and see if it happens all the time or only with hubs locked. If it happens all the time then you can exclude the front end stuff I mentioned.

I believe we've checked the outer wheel bearings on the front. Also thought I'd add that the problem has been intermittent. We don't think it's in the front because when it first started acting up it had auto hubs and the actuator cams were missing so the front axle could not engage.

cheasfridge said:

I believe we've checked the outer wheel bearings on the front. Also thought I'd add that the problem has been intermittent. We don't think it's in the front because when it first started acting up it had auto hubs and the actuator cams were missing so the front axle could not engage.

Click to expand...

Still an easy check, unlock the hubs, if it still happens intermittently you are confident it isn't the front driveline (but still can be a front brake rotor issue)

make sure to check fluid levels in the trans and transfer case. is the dragging only when there is the vibration, or all the time? it sounds like rear brakes to me, if it were in the front, it would pull pretty hard to one side with what you have described. I would replace the rubber brake line to the rear end, fairly cheap and easy

Hey, I'm the dad and just got back into town wanted to add a couple of quick points.

The transmission does look like it's been rebuilt recently, it is much cleaner than the surrounding hardware. I still kind of like the transmission for this if it wasn't for the fact that when it first started acting up it was driving down the road at highway speed in 5th and when it did it to me I was in 2nd. I don't think those gears have anything in common.

I will check the fluid levels tonight.

I decided last night I was going to pull the rear rubber line to bring into town to get a replacement and it's obviously been replaced in the last few months as well.

I was going to pull the axles next even though I can't feel anything in those bearing and cannot see any issue with the rear cover off the rear end just to double check those bearings.

The drag only occurred when the vibration happened to me. I pulled over backed up turned and headed back to the house. I got it back to the house jacked it up and all four wheels rolled free and I could not see anything. I have no way of knowing if backing up some released something or just stopping did it.

I drove it another 30 minutes trying to get it to do again and could not. I was thinking it was the parking break not releasing but I must of set and released that brake 30 times to no avail. The rear brake inspection certainly did not show any sign of being hung on no excess brake dust, no one side worn down worse than the other.

I assume a rear output bearing in the transmission could cause symptoms like these? If that's the case there would be no way to test that theory short of pulling the transfer case and tranny to get inside it correct?

Another thought,

I know the transmission been out semi recently, what if they failed to put in a pilot bearing or pushed into the crank? Maybe the transmission input bearing was good enough to hold it for while but as time goes on the bearing cannot take the strain and now it's allowing the clutch to be clamped off center?

I think when I drove it the problem occurred when I shifted to 2nd.

Just an update: Today we pulled the rear axles and checked the bearings, they were fine. We also pulled the transmission and transfer case and checked the pilot bearing and it's good. The clutch is wore almost down to the rivets, and there are signs of slipping on the clutch plate. We aren't 100% convinced that that would be causing or problems however. There is some kind of fly-wheel gear and sensor in the rear end that we were wondering about as well.

We're hoping this might ring some bells for someone. As of right now our next move will probably be to have somebody crack the transmission and transfer case open for us.

the gear and sensor in the rear diff is for antilock brakes. rotate the trans by hand in all gears, both directions, and feel for binding. if it has a bent shaft it may get tight, then loose, causing vibration