Problem with Death Wobbles in a 2wd

[Eric M.]

I've got a friend who's experiencing Death Wobbles (steering shimmy). He's got a 2wd, 75 GMC dually that experiences death wobbles at about 80 MPH. Yes, I told him a 75 GM dually was never built to go 80, but, he's owned it for years and it never Wobbled before.

All the front end is new, new steering box, alum. Weld rims, he's tried several sets of tires. Shocks good, brakes checked.

Any ideas?


Thanks,

Eric M.

[boxrodz]

I presume that he has had his new wheels balanced and when you mention that his front-end is new that he has replaced the ball joints, bushings, center link, tie rod ends, pitman and idler arm. Did he have a front-end alignment afterwards? My guess is that the problem is in the front end suspension (alignment or setup).

[jimmmie '79 Cheyenne]

Pulling this from way back when I worked at a frame and wheel shop - If the caster is either too little or too much (can't remember which) , it can cause a shimmy at high speed or when you hit a bump at a lower speed.

[Bad Karma]

I had a wobble at exactly 45 mph in my Suburban, I chased it for a while, then gave up. I always assumed it was coming from the front end. It finally disappeared when I replaced my wasted rear spring bushings while I was doing my flip kit.

Maybe the rear end is out of whack a little or possible driveline vibes? At 80 mph, who knows...

[Eric M.]

Originally Posted by boxrodz

I presume that he has had his new wheels balanced and when you mention that his front-end is new that he has replaced the ball joints, bushings, center link, tie rod ends, pitman and idler arm. Did he have a front-end alignment afterwards? My guess is that the problem is in the front end suspension (alignment or setup).

Yes, he's done all the above mentioned. He did realign the front after his work and has played a bit with the castor (he's still playinh around with castor settings). He had the truck on a dyno up to 120 MPH and no vibration from the rear.

Thanks,

Eric M.

[84 400]

Hmm this is very interesting. If it was not doing it before it would lead me to belive that somthing was done wrong during the front end rebuild. Not that i am doughting his work but that could be a possible reason or a defective part. Also how is the steering colum its self? any play in that? Is it lifter? ALso do you have any pics of the truck? i know it is off topic but a dooly pulling those kind of speeds must be a pretty cool truck

[Eric M.]

I'll have him check out the steering column. Not lifted, he uses it for towing his boat.

Here's a link I posted from a while back, it's more about the boat, but there is some info about the truck.

Half way down the page, after the Blazer and the goofy animal pics. (I swear, that's not me

http://blog.mannon.com/archives/000004.html


Thanks,

Eric M.

[84 400]

wow those are both sweet the black and white one. If i had the money i would buy a 80 dualy suberban and drop a motor like that in it with a 6 speed trans and lower it just a bit. That black truck is sweet

[magnethead]

we've gotten my dually to 90 MPH. Unfortunately, that also made fuel comsumption be around 90 gallons per hour (lol)

[lurch115]

have him check all the rear suspension parts too....an easy way to find out if something is worn out such as leaf spring end bushings or if the leaf springs them selves are bad is to drive down a smooth road and rock the steering wheel back and forth...if the back end seems rather loose, or dips to one side then something is worn out...

[crazy longhorn]

He!!, that old dually should run 100 mph + with no "wiggles". If it were mine, I would have the balance on the fronts checked again.....& if that dont get it, I would look at drive shaft issues, or driveline angle problems. Best of luck... L

[84 400]

Rear leafs could be it to my freinds does that same thing because his are shot. with towing and all maybe your freinds are worn ?

[magnethead]

Originally Posted by 84 400

Rear leafs could be it to my freinds does that same thing because his are shot. with towing and all maybe your freinds are worn ?

x3

my rear springs are all but flattened out...

[Eric M.]

It isn't coming from the rear. See the above post. He put the truck on a rear wheel dyno and ran it up to 120 MPH checking for vibrations. Nothing. It isn't coming from the driveshaft, balancer, rear tires, rear leafs or any part of the rear suspension. It would've showed up when on the dyno.

Thanks,

Eric M.

[mhicks]

Tire separating? I have had that happen before and could not see it.

[72C203503ONTHETREE]

The truck is tied down tight on a dyno, the springs are loaded. An unloaded rear end will allow the loose bushings/springs to get loose and vibrate. Try jacking the trucks rear up on jack stands and the run it up to 80-90 mph but be very careful.

[84 400]

i agree with the above post but it is very very dangerous!

[Eric M.]

Originally Posted by mhicks

Tire separating? I have had that happen before and could not see it.

He's on his second set of new tires in 2 months (trying different brands) and no difference.

Thanks,

Eric M.