Diagnosis Requested: Thumping

[Riotnrrd]

Hi folks;

I have a 1979 F150 4x4 (new to me a couple months ago). I've had some events lately described as follows:

Start truck up, proceed down road approx 35-40 MPH

Usually going around a left hand corner at about 35-40, wheel starts to shake a little. After straightening out, a SEVERE THUMPING / POUNDING BEGINS. I can't tell whether its coming from the front or the back, but its pretty severe. I pull off the road, check obvious things, nothing seems wrong.

Usually I start the truck up again and it proceeds with no further problem, but lately it seems like its getting worse. Again, the steering wheel starts to shake a little, a SEVERE pounding or thumping begins, but it usually goes away (not always, though).

I took a closer look under the front end yesterday. Its pretty clear there's at least 2 things wrong.

1) I have a leak in my power steering gear. I'm not sure where its coming from yet (one of the seals probably), but I've got bubbles in the air reservoir and it seems like its getting worse. Inspecting the coupling between the steering shaft and the power steering input, it looks like the flange on the steering column side is visibly bent / warped.

2) I have a horizontal shock absorber (steering damper?) that's bent. about 5 degrees, so obviously its not going to work.

3) It looks like the bushings on the steering linkages are fairly worn. I'll inspect them closer tonight.

I currently plan on doing the following:
- Identify leak location in the power steering gear, replace seals / repair as needed
- Replace the coupling between the steering column and the power steering input
- Replace the bent steering damper
- Replace any bushings that are obviously worn
- Possibly inspect or replace the Left Hand tie rod end (I think there's only one on this 4x4, along with an adjuster nut that can also be replaced).

Front wheel bearings SEEM fine, there is no discernable movement in or out on the front. The right rear has some obvious play, so it might need to be adjusted / replaced.

QUESTION: Am I on the right track here, or are there other things I need to be looking at? What are some of the likely causes of this sort of issue?

I'll be getting some new tires as soon as I can drive it to the shop safely, currently have 33x12.5 R15 Thornbird mudders of some sort, in rough shape. Plan to install Uniroyal AWT IIs as they are a cheap AT option. I plan to use the truck mostly for light hauling and some offroading.

ANY INFORMATION WOULD BE APPRECIATED, THANKS!

 

[LEB Ben]

Usually thumping is associated with u-joints. Since it's while you're taking a turn, check where your steering box is on the frame, is the frame cracked, is the box loose? I'd also check for tie rod and ball joint wear. You may also want to check for trac bar, sway bar and drag link bushing wear.


Another thing just to clear the air...at those speeds and taking a turn, what's the possibility your tire is catching a fender or radius arms?

 

[1985 Ford F-150]

Hows the ball joints look? Id jack the front end up and start shakin the tires and see if theres any movement other than normal. Then go take a look at the tie rods and drag link. Another possibility is a U joint went out in either one of the drive shafts or one of the front axle shafts.

 

[Riotnrrd]

Usually thumping is associated with u-joints. Since it's while you're taking a turn, check where your steering box is on the frame, is the frame cracked, is the box loose? I'd also check for tie rod and ball joint wear. You may also want to check for trac bar, sway bar and drag link bushing wear.


Another thing just to clear the air...at those speeds and taking a turn, what's the possibility your tire is catching a fender or radius arms?

Thanks for the advice, I'll check that out.

I don't THINK it's the tires because the noise, etc continues after I straighten the wheel. But I'll check that too.

 

[Jotun]

Hows the ball joints look? Id jack the front end up and start shakin the tires and see if theres any movement other than normal. Then go take a look at the tie rods and drag link. Another possibility is a U joint went out in either one of the drive shafts or one of the front axle shafts.

This is what I would do. I had ball joints go bad a few years ago and whenever I would turn or hit the brakes hard the truck would shudder like it was going to fall apart turned out to be the lower ball joints....

 

[1985 Ford F-150]

Also just remembered check the radius arm bushings as well.

 

[Riotnrrd]

Usually thumping is associated with u-joints. Since it's while you're taking a turn

Another question... what if it happens when I'm NOT in a turn... same diagnosis or a different problem?

 

[1985 Ford F-150]

It can if theyre really bad but youd mostly hear it when ya get on and off the throttle.

 

[73F100Shortbed]

It could be any one of the things you mentioned. I would fix the bent dampener. Check tie-rods. Definitely check your ball joints and u-joints. I had a slight thumping when coming to a stop for a few weeks now. I thought it was my front brake pad rattling but I was under the truck today to adjust parking brake to pass inspection and I figured I'd check the u-joints. Well my driveshaft is about ready to fall out and they don't even have 30k on the joints and I grease them regularly. Good thing NAPA had both joints and it only cost me $20. So that's tomorrows project. Definitely check them over to be safe. The ball joints would be my first thought to check given what you are describing. Ben also makes a good point about checking where the steering box mounts to the frame. If there are cracks and can cause problems. Radius arm bushings is another good suggestion. Sometimes if they are bad you will hear a thud when hitting the brakes as well depending on how bad.

 

[cipsmithers]

As previously stated, check the trac bar bushings. mine went and every once in a while at higher speeds, it would create a horrible shudder that would force me to stop. refered to as the death shake. just an idea

 

[LEB Ben]

Another question... what if it happens when I'm NOT in a turn... same diagnosis or a different problem?

Yeah...same diagnosis

refered to as the death shake. just an idea

Death WOBBLE.

 

[Ranger429]

Death wobble sounds exactly like what he has. Once it starts to shake back and forth vigorously it will develop that thumping sound.

I would check the trac bar bolt on the axle side. It could be wobbled out allowing free movement of the trac bar. If it is worn replace it with a tapered bolt.

 

[Alvin in AZ]

Title sounded like a tire with a belt problem from sitting flat too long.
Post sounded exactly like "death wobble" to me.

Do your king pins and bushings along with anything else you can find
play in, in the steering stuff. BTDT and fixed it first time. There's a
recent thread about this, and for him, it was only the "end play" at
the king pins causing it. But he already had everything else "right"
or newly replaced.

Since you aren't in the "rust belt" it might not bee too bad of a job.
Here, it's a cinch! Your's will prob'ly be somewhere in between?

Alvin in AZ

 

[Riotnrrd]

Death Wobble is a rather discouraging name for a newbie like me! But it appears pretty common, and not what I'd assume it means as "piece of junk"!

Checked some stuff out today. The radial arm bushings on the frame brackets are in pretty bad shape. However...

It looks like it might be the front driver's side lower ball joint. I jacked it up and shook on the tire. When I lift on the bottom of the tire, it pulls out about 1/8th - 1/4th of an inch. The top ball joint looks solid, but the bottom ball joint has a LOT of free play. I looked at the passenger side for comparison and both joints appear to be rock solid. But the left one definitely moves in and out.

I'm guessing that 1/8th or more of play in the lower ball joint on the driver's side is a bad thing?

1985 Ford F-150 gets the prize of a dirty shop towel, with an honorable mention to Jotun and 73F100Shortbed. After I replace it, if the problem goes away, I owe you guys a beverage!

 

[73F100Shortbed]

That sounds like alot of play. I would change it. You will at least eliminate part if not all of the problem.

 

[LEB Ben]

1985 Ford F-150 gets the prize of a dirty shop towel, with an honorable mention to Jotun and 73F100Shortbed. After I replace it, if the problem goes away, I owe you guys a beverage!

Hey hey hey...what about me??????????????

I'd also check for tie rod and ball joint wear.

 

[Riotnrrd]

Sorry, UTfball68! On second read, you were the first to suggest ball joints!

Now if I can just figure out how to replace them I have the factory manual (which is somewhat hard to read) and a Haynes (which is somewhat different), and the Internets, so between the three... hopefully I can figure it out!

I don't have a lot of 'special' tools, so I might have to borrow / rent something from a parts store... like a ball press!

 

[smokey]

You don't need special tools to change them out but the press sure makes it easier.
While you have it apart do the upper and lower. Wheeenone is worn the other is worn also. no use having to tear it apart again a few months down the road.

 

[1985 Ford F-150]

Yeah do em all then and there along with the radius arm bushings.

 

[LEB Ben]

Heard a tid bit of advice that I'm gonna try in the next few weeks when I do ball joints. Before you put the new joints in, freeze em, supposed to let them slide in a lot easier. Dunno how true it is, but it can't hurt.