Keeping it straight. On the straight-a-way.

[Accelo]

I have lowered trailing arm truck with coils and an aftermarket posi.
I have a difficult time keeping my truck tracking straight when the tires are spinning. The oscillations get really bad and counter steering helps but there is no way to stop them unless you back out of the throttle. I would hate to be the guy that fails to negotiate the straightaway!

I have several theories and one is the stupid design of the aftermarket rear sway bar. I plan on disconnecting it to determine if it makes a difference or not.

Wondering if others have the same issue and if, and how, they have solved it"

I am including a fun link to a 1200 HP C10 that has none of these issues and over three times my horsepower. Different chassis dynamics of course but none the less the video is a hoot and I highly recommend it. This is the video that made me thing the "under power" handling of my truck is not normal.

https://www.youtube.com/watch?v=kIegHrKkoak&t=125s

Wondering out loud, what his tire cost is per year? I think he toasted a set just for the video.

[geezer#99]

I removed the rear sway bar on my 84. Helped a bunch with ride and handling.

But maybe your problem is all in the front end alignment.
What’s your castor angle?

[HO455]

What kind of shocks on the rear?
What kind of bushings are in the trailing arms?
Do you have a long adjustable track bar?
Have you centered the rear end and then checked the rear alignment?
What kind of aftermarket LSD did you install?

It's too bad they didn't show the chassis while it was still on the lift. You could see what they have done to it.

Comparing horsepower can be misleading. That truck could have issues, but until it starts to hook up you won't know.
I've had and seen hard running cars that are burn out kings, on the street turn, into evil handling widow makers the minute you bolt a set of slicks on them.

[Accelo]

What kind of shocks on the rear?
Belltech, lowering style short shocks in the stock location.

What kind of bushings are in the trailing arms?
Stock rubber bushing, all are new.

Do you have a long adjustable track bar?
Yes, it is adjusted to center the diff.

Have you centered the rear end and then checked the rear alignment?
4 wheel thrust alignment was completed. I don't have the print out.

What kind of aftermarket LSD did you install?
What is a LSD? (Locker)?
Will have to look that one up. I still have the box.
Cheers

[yuccales]

Thanks for the link. Love his "pull away". Hope you get your handling worked out.

[72c20customcamper]

Originally Posted by Accelo

What kind of shocks on the rear?
Belltech, lowering style short shocks in the stock location.

What kind of bushings are in the trailing arms?
Stock rubber bushing, all are new.

Do you have a long adjustable track bar?
Yes, it is adjusted to center the diff.

Have you centered the rear end and then checked the rear alignment?
4 wheel thrust alignment was completed. I don't have the print out.

What kind of aftermarket LSD did you install?
What is a LSD? (Locker)?
Will have to look that one up. I still have the box.
Cheers

Limited slip differential. The geometry of the rear will have an effect on the way it handles under hard acceleration . I’ve seen cars actually twist launching . My Chevelle used to go sideways when I romped on it . I put Frame stiffeners in the back along with adjustable tubular control arms from UMI helped immensely.

Never made a high performance truck but could it be the rear is squatting down which causes the track bar to push the rear to the right causing tracking problems ? Just spitballing

[HO455]

Originally Posted by Accelo

What kind of shocks on the rear?
Belltech, lowering style short shocks in the stock location.

What kind of bushings are in the trailing arms?
Stock rubber bushing, all are new.

Do you have a long adjustable track bar?
Yes, it is adjusted to center the diff.

Have you centered the rear end and then checked the rear alignment?
4 wheel thrust alignment was completed. I don't have the print out.

What kind of aftermarket LSD did you install?
What is a LSD? (Locker)?
Will have to look that one up. I still have the box.
Cheers

Personally I'm not a big fan of Belltech shocks. I've run them on my S10 and the bounce control isn't great and after 25k miles they're toast. That being said if yours are new they shouldn't be the problem.

New bushings are good! Your track bar looks nice. Having the axle centered with each wheel the same distance from the frame rail before the alignment check will reveal if you have a bent axle housing.

LSD= Limited Slip Differential. The proper name for any kind of axle that forces power to both wheels under acceleration. They all have some amount of difference in the power applied to each wheel.

Can you explain more the oscillations you are experiencing?

Does the truck always got te same direction?

Is the truck moving sideways immediately or does it happen once the tires start to hook?

If you have the ability to video the rear suspension it may show what is happening.

[Sheepdip]

Make sure your seat belt is on while trying to sort this out! Safety First!

https://www.youtube.com/watch?v=XigUXvVR-xw

[kwmech]

Track bar off, not keeping the axle centered or axle not square to the front end?

[yuccales]

Originally Posted by Sheepdip

Make sure your seat belt is on while trying to sort this out! Safety First!

https://www.youtube.com/watch?v=XigUXvVR-xw

That dudes back must have hurt.

[kwmech]

I can certainly see why the comments are turned off

[Accelo]

This is the locker I installed.
I am unsure if it goes to the same side first or not.
Kind of busy when it happens. LOL.
Maybe I can get a video? One where I stay in the vehicle!
Unlike the guy in the video.

[Boog]

It's worth mentioning the crown of the road surface contributes to a tire spinning car running more sideways than on a flat surface road. Torque steer also. As the truck torques over to the right it plants the right rear tire harder than the left and will cause it to go sideways.
Big boy fell smooth outta the 'maro.

[Accelo]

Feedback on how I solved the handling issue!

It was finally dry enough to drive my truck today.
I had previously pulled the rear, aftermarket, sway bar.
Now it tracks perfectly under power.
Because it's cold getting traction was minimal, perfect testing conditions.
Truck has no issues spinning the tires loose at 35mph.
Tracks straight, drives fine. GM knew what they were doing.

Now my rant;
How dare the even sell this crap rear sway bar. I can't even prove it helps in the corners.
I am confident someone found a bar the right width and said, Hold my beer and watch this!"
No testing, no install instruction either.
I do know it will kill you if you don't back of the throttle with the POS bar installed.
I have found other postings that have identified the same issue.
Now, with the bar removed, it will safely do something totally illegal.
Somehow I feel better now because it was unsafe and illegal.
I get the irony, fun stuff.
Glad to get this off my chest.

Still can't believe they sell this crap to the public.
And they will not stop till some gets seriously hurt and has a really good lawyer.

A link to the POS rear sway bar;
https://www.classicindustries.com/pr...E&gclsrc=aw.ds

I am confident all sway bars do not fall into this category. This one does. It is also one of the least expensive. Lesson learned.