Violent Shake at 60MPH

[BillsFan76]

Here is the second issue with my recently purchased 69 Bronco Sport I'll tackle this after the electrical issues are corrected but wanted to ask and get some ideas.





The truck has a really scary shake at around 55-60mph. The owner who has had the truck since 1995, said the front end has never had any work done to it and is in need of a rebuild. There is no shaking or pulling at all till it's at highway speed. The alignment is solid (no pull or wander at lower speed or even highway speed for that matter), steering is tight on it, and the tires have good pressure.. It has the factory Dana 30 in it by the way. What in the front end would cause such a violent shake at that speed? Would worn out ball joints do that? I didn't drive it past 60mph but he said at higher speed the shake actually goes away. I wasn't willing to find out so took his word on it. I've never done front end work on anything so any suggestions on a solid starting point are appreciated. Thank you again everyone.





Alex

[TOOLMAN]

The 'death wobble' is usually due to worn out track bar bushings and/or crappy front tires.

[colby45]

I just went through this same issue on my '66. New track bar bushings and new tires did the trick for me. Completely eliminated any death wobble. I'd usually get it around 40 or 45.

Also, congrats on your purchase! That's a great looking Bronco.

[Gunnibronco]

Just read through this the other day, a good explanation of all the possible causes of death wobble. Basically any worn component in the front end can cause it. Or a combination of worn stuff.

http://classicbroncos.com/forums/showthread.php?t=89266

[colby45]

Yes that is true. Here is another really good technical article on how to assess what things in the front end could be causing the wobble. I referenced this a lot as I was working through my own wobbling issues.

http://www.wildhorses4x4.com/product/de ... e/tech_faq

Track bar bushings can be a major cause if they are worn. They are pretty easy and cheap to replace so I would say start there if they seem worn. Old out-of-balance tires can be another major cause. If you know the tires are old or worn (Like in my case they were 30+ years old) you might consider replacing them also, especially if the steering feels tight and well aligned otherwise.

[BillsFan76]

The steering is pretty tight, tires look almost brand new, and alignment is pretty good. Maybe a slight pull to the right but very minor. Ill put it up on a jack this weekend and shake the end a bit and see what seems lose and moving. Thank you all for great advice and a good place to start. My guess after reading through these is worn out track bar bushings as the owner said nothing on front end has ever been replaced. Will update this as I find out. Thanks everyone.

[Jesus_man]

Best thing to do is leave it on the ground, and motor off. Have someone steer the wheels back and forth, as in move the steering wheel from 11 to 1 o'clock. While they do that, check the steering shaft as it comes thru the firewall and check that the joints there are tight. Watch the steerbox at the frame and make sure it's tight there as well, no flexing. Then check the pitman arm connections, down to the drag link, down to the axle, and then track bar bushings. It's usually one of those things, or a combination of them.

Having it at 55mph is unusually high, and more scary!

Then maybe put it on jack stands and check for bent rims or any wobble there. If you're not finding anything, put the rear tires on the front and test again.

[BOBS 2 68S]

I also go with the track bar bushing and or tires. Mine had the wobble, every thing looked good. I changed the track bar bushings and worked with the air pressure, wobble went away.

[sykanr0ng]

I have had an out of balance tire that would only start to shake above a speed on the highway. (strangely enough about 55 mph)

Having them checked on a spin balancer is cheap and may solve the problem faster than throwing parts at it.

I was taught that the first rule of mechanical diagnostics is to start with the simplest or cheapest.

Once had a co-worker that had the same problem, I sent her to a different shop than the first one which was claiming there was no problem with the tire balance, after the second shop balanced the tire the shake went away.

[BillsFan76]

Good idea. I'll try that this weekend and go from there.

[B.O.B.]

Depending on where you are at you can try to bring it over to my shop. I work at Discount Tire on smokey hill and Buckley in Aurora. I'll check the balance and see if anything else might be out.

[BillsFan76]

Sent you a pm B.O.B, thanks man.

[BillsFan76]

After finally having a day off to stop by Bob's work, he took a look and noticed a janky piece on the steering setup. The previous owner mentioned he had broke a steering piece on the trail and had to do a makeshift weld to make it back. Hoping that piece ends up being the majority of the shake when driving highway speed. He also looked at the tires and even though they look brand new and full tread, they're 13 years old lol Didn't bother with checking the tire balance due to the piece that was welding looking so shoddy, if replacing this doesn't fix it, I'll look into the track bar bushings and the tire balance. I believe the piece I need replaced is called the adjustable drag link.

I'll attach a picture of the weld and the piece I need then post in the parts wanted section to see if anyone has one they may have upgraded from that i can buy. Thanks everyone for all the help and guidance and thank you B.O.B for offering to take a look, I really appreciate it. Great group of people here.

[Rox Crusher]

I don't want to sound like your mom, but man..........I wouldn't drive that thing another foot without fixing it first

[Justin]

If you look up "janky" in the dictionary, there's a picture of that repair. Whether it fixes your problem or not, that needs to go.

[TOOLMAN]

Looks like you're going to need a drag link and probably a pitman arm. It looks like the 'janky' repair involved doing something weird with the connection there.

[landshark]

Looks like you're going to need a drag link and probably a pitman arm. It looks like the 'janky' repair involved doing something weird with the connection there.

Thats a 66 steering setup too if iam not mistaken?

[BillsFan76]

I couldn't really tell from looking at it if the Pitman arm could be reused or not but the drag link definitely look . Going to make a post in the parts wanted ad looking for that drag link and Pitman arm now. If anyone is looking at this has a stock drag link or Pitman arm laying around that they want to sell, please send me a message, i'll buy it. Thanks again everybody.

Alex

[Digger]

While you're checking things, look for cracks in the frame around the steer box. My buddy let a death wobble issue go too long and it ripped the steer box from the frame. Luckily at low speed.

[BillsFan76]

Will do, thank you.

[Gunnibronco]

If you have trouble finding a stock pitman arm, check with Don Allison (dalli is his screen name here) he has a salvage yard with a lot of good Bronco parts at fair prices. I got a pitman arm from him.

[BillsFan76]

If I can't find it locally I'll definitely go that route. I spoke with him through emails recently about a hard top, really nice, very knowledgable guy.

[hockeydad4-22]

While you're checking things, look for cracks in the frame around the steer box. My buddy let a death wobble issue go too long and it ripped the steer box from the frame. Luckily at low speed.

Also check the frame around the track bar bracket as well. I can testify and show you pictures of what can happen there. My son ripped the track bar right off the frame, taking a fist sized chunk with it. Bad news at any speed!