INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Uniball suspension pins shearing off

Uniball suspension pins shearing off

(OP)
I have a lifted Chevy 3500 HD and I have now sheared off two uniball pins in my lower control arms. I am a back yard mechanic and really like to DYI.

I need help in setting up the IFS with the lift. Many have said to remove the IFS and replace it with a straight axle. I have read many posts that state that most don't understand IFS so they want to rip it out and replace it with a straight axle.

I need to fix my current problem of the broken pin but need a stronger steel to make this work, but I would also like to know how to correctly set up my IFS if anyone can help me.

Here is a link to some of the pictures I have taken of the suspension and how the pins keep breaking.

http://imageshack.us/g/1/10007382/

RE: Uniball suspension pins shearing off

(OP)
I forgot to add a few things to the thread.

I did have a new pin turned down from 4140 and it seems to be holding up but really want to know if I should get another one turned out of 4140?

RE: Uniball suspension pins shearing off

I couldn't figure out how to view or download your images.

Mike Halloran
Pembroke Pines, FL, USA

RE: Uniball suspension pins shearing off

I think you've probably exceeded the articulation angle of the ball joint, so as the spindle moves up and down, the ball locks up, and transmits a torque into the pin, and so it breaks. Try limiting your suspension travel so that the ball doesn't over artiuclate, or redesign the spindle so that it uses longitudinal axis cross axis joints.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Uniball suspension pins shearing off

(OP)
Are there any good sites out there that help teach you how to measure the proper angles and travel of the tire?

RE: Uniball suspension pins shearing off

A few years ago, there was a fad of fitting ridiculously small tires on wheels with a large positive offset (tire spaced out) to cars of all kinds.
I saw one car on which the modification actually looked good; it was a Mercedes, of all things. On everything else, they just looked like roller skate wheels.
The fad disappeared pretty quickly, I think because of widespread reports of wheel bearing failures occurring within a week of replacing the wheels.

The wide tires you have fitted, and the super thick wheel spacers needed to gain inside face clearance for them, are certainly not helping your wheel bearings, because you've moved the contact patch outward, a lot, from where it's supposed to be.

It occurs that the contact patch position probably also applies some extra lateral force to the lower ball joints, just from the weight of the truck multiplied by the larger moment arm, in addition to any increased steering effort associated with the modification.

I'm guessing that your problem might go away if you go back to the stock wheels and tires on the front, and ditch any spacers you installed, also.

I'm also guessing that your replacement 4140 part is probably already bent.


Another possibility, not mutually exclusive, is that you got a mismatched lift kit, i.e. some parts meant for a 5" lift and some parts meant for a 6" lift, or whatever, so that the geometry of the IFS relative to the road is not the same as it was before. I'm not familiar enough with modern Chevrolets to tell anything about that from the photos.

Mike Halloran
Pembroke Pines, FL, USA

RE: Uniball suspension pins shearing off

The way I always test off road suspensions for binding is to jack the corner up and support on a stand, then remove the wheel and the spring, then use a trolley jack under the hub or brake or spindle and jack the suspension through its full range while also turning from lock to lock.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules

RE: Uniball suspension pins shearing off

(OP)
I don't think that the kit is a mismatch but there are large spacers behind the rims. I will have to check clearances but I believe that they are on there so they don't rub either the steering knuckles or inside fender well.

I did reach out to the original owner and the tires that are currently on the truck are 1 inch wider than when he owned it. The second owner must have put wider tires on. I will look at getting this corrected when I replace the tires. I will try removing the spacers to see if that buys me anything.

Any sites that anyone can suggest on lifted IFS? I really don't want to put in a solid axle but also don't want to have a major accident because of this pin.

RE: Uniball suspension pins shearing off

I'd sure check what Greg L and Pat P said about binding before, or in parallel with wheel and tire changes.

One thing to check might be signs of contact between the stud, and the opening in ball joint seat. There shouldn't be any.

Do you already have something like this?http://www.pirate4x4.com/forum/chevy/1103878-long-...

RE: Uniball suspension pins shearing off

So, have you got _any_ OEM parts remaining?

Greg and Pat are right; you need to remove the springs and run each spindle through its entire range of motion, checking for interferences, and for small clearances that can close up under dynamic loading.

... preferably before you drive it again.
You've been lucky so far, collateral- damage wise.

Mike Halloran
Pembroke Pines, FL, USA

RE: Uniball suspension pins shearing off

(OP)
Not very much OEM parts left the CV's are stock, but the rest of the front end has been replaced. I ordered a couple of books to see if I can get more educated about IFS. I ordered "tune to win". I was also looking at ordering these has anyone used or have any experience with them?

http://www.rcvperformance.com/categories-cv-axles....

RE: Uniball suspension pins shearing off

If you needed CVs with more articulation range, the ones you have now would have exploded already.

I suppose the obvious question is, "Are the Uniballs you're using now, the exact parts that were intended to be used in your LCAs? The failure you report suggests that the Uniball itself is lacking in articulation angle, as if the outer race is wider than the one for which the LCA was designed. Or maybe the shank of the pin above or below it is too large, giving the same effect.



Mike Halloran
Pembroke Pines, FL, USA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close