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The Importance of changing out stock track bar and lower control arm bolts

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The Importance of changing out stock track bar and lower control arm bolts

 
Old 12-20-2011, 09:48 PM
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Default The Importance of changing out stock track bar and lower control arm bolts

Saw this on the net and figure I post it here, really surprise me that Jeep has not corrected this.


Everyone here on the forums has heard or has experienced death wobble. Most of the time it is due to track bar bolts not being tight enough and causing damage. Most people DON'T know is that the bolt is a 14mm but the whole for the track bar and bushing is 9/16. Thus we have a small clearance issue. The track bar only stays in place due to a clamping force on the sides BUT the REAL problem is that the bolts are completely threaded to the head vs using shoulder bolts to contact the area of the bushing only. Doesn't sound like a big deal right? I'll let the pictures do the talking. I installed my lift kit and track bars, I've done everything my self and tq them to spec. My lift kit and track bar has less than 1,500 miles on it!!










Notice the thread were "eating" in to the metal sleeve in the bushing. Now I'm not hard on my jeep and have only taken it off roading once since I've had it. I know its a crime, but the importance I'm trying to show here is that it is a very good idea to change out the bolts on the control arms and track bars to shoulder bolts to prevent damage and to also avoid death wobble.











The bracket holes and the control arms/track bar holes are 9/16 but the bolt is 14mm.

14mm=0.5511"
9/16" =0.5625"

as you can see that .0114 + the clearance of the actual hole does make a difference and a big one at that. Everything has been tq like it should and has been check. This is not install error of why this happen. Also combine the fact that the track bar bushing rides on the threads of the bolt, meaning less surface are and thus the threads act as teeth cutting in to the bushing when you start to flex or driving around on.




The numbers don't lie, common sense is well common. Proof if proof.

I've been wrenching for nearly 10 years and when I saw this I was actually shocked, not what I found but during the install how the bolts aren't shoulder.

The problems are:

The holes for the track bar and the bracket are 9/16 while they use a 14mm bolt which is smaller. This causes a clearance issue of .0114
the bolt is not shoulder, thus causing the load to be put on the threads, image walking on razor blades that are vertical (extreme I know but this is to show my point) Now add twisting from the axle going up and down on the track bar and control arms. You have the threads now cutting in to the sleeve because of Problem number 1
The clearance over time can make the hole like a oval and you can experience death wobble or even before that. As movement is easy through this.
Since the size of the holes are off, once you tighten the bolt down it clamps on to the sleeve to hold it in place but the bolt can still move in/around the holes because of the clearance above, this over time will cause damage.
The TQ is implied through the head of the bolt, the bolt will twist due to friction first and then start to turn. So after it is said and done with you really might not have 125/150 lbs where it should be. AT THE NUT! But in this application is hard to do so. But because of problem 2 with the threads will cause more friction and more friction means more inaccurate tq read out.

The dealers will be pointless to go to. Why? They sell and fix cars, not engineer them. They will blow you off as if you are the person saying the world is going to end on Christmas.


All in all it is a design flaw, I think the TJ are the same way and while there are hundreds of thousands of jeeps on the road (JK and TJ) I personally feel a lot of the DW could be avoid by using the right size bolts. Sorry if I sound like I'm repeating my self I have two threads going on.


WATCH THE VIDEO! IT SPEAKS FOR IT SELF IN THIS MATTER.

Last edited by Robar; 09-02-2012 at 03:02 PM. Reason: Edited video
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Old 12-20-2011, 09:59 PM
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Thanks for that post. I found it held quite a lot of information
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Old 12-21-2011, 12:37 AM
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Default Trackbar holes

yes, i found this out 12 months ago, and changed all bolts. the other issue is that the hole in the chassis mounts is also large. they are pressed and not drilled, approx 15mm for the outer hole, and approx 16mm for the inner on both trackbar and LCA's. I have welded washes in to correct this?
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Old 12-21-2011, 01:07 AM
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Originally Posted by matzjeep View Post
Hey do you have specs on the shouldered bolts your using? grade 8 9/16, how long and how much shoulder?

Thanks for the post.
Originally Posted by AussieTom View Post
yes, i found this out 12 months ago, and changed all bolts. the other issue is that the hole in the chassis mounts is also large. they are pressed and not drilled, approx 15mm for the outer hole, and approx 16mm for the inner on both trackbar and LCA's. I have welded washes in to correct this?
I'm still researching this. The chassis I side I haven't got to test but if they are anything like the axle side it is 9/16 NOT 15/16mm.


Grade 8 will do, I would get washer for each side as the stock bolt has a FLANGE HEAD, which is like having a "built in washer" I would also get locking nut/washer as well. The ones I use are called deformed locking nuts.

The following is for the front and rear LOWER control arms axle side and frame side and both sides of the track bar (axle and frame). I haven't gotten to the uppers just yet. If anyone had time to look at those well that be awesome if not, I'll get to them after Christmas. The shock and sway bars ( sway bar only applies to some aftermarket kits. Example I the sway bar links that my teraflex 3 inch lift came with use the wrong bolts. All shocks need changing as well as they are not shoulder bolts.

MAKE SURE THE BOLTS ARE FINE THREAD (UNF) !!!
  • 8) 9/16-18 UNF x 4.0" long (LCAs)
  • (4) 9/16-18 UNF x 3.0" long (TBs)
  • (12) 9/16-18 UNF lock nuts
  • (24) 9/16" Extra Thick hardened flat washers
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Old 12-21-2011, 03:25 AM
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I just changed my trackbar bolts out to grade 8 9/16" fine thread bolts last week after my first battle with death wabble. I was also thinking I should look at my control arm bolts too. Thanks for the heads up.
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Old 12-21-2011, 04:11 AM
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Awesome post. I'm experiencing just a tiny bit of dw on larger bumps/pot holes. Gonna go look for these bolts after work today. I'm a little nervous to see what mine might look like. I'm a about 32k miles and 2 years on my suspension setup. 60k miles total on my jk. I'll report back my finding.
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Old 12-21-2011, 04:31 AM
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Priceless post...thanks for all the good info. My to do list just got rearranged, all lca's and track bar bolts just got bumped to the top of the list!
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Old 12-21-2011, 05:14 AM
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Great post....will have to see if the local parts store has all the bolts you listed. Thanks for the info!
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Old 12-21-2011, 05:22 AM
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Originally Posted by SlowJK View Post
I'm still researching this. The chassis I side I haven't got to test but if they are anything like the axle side it is 9/16 NOT 15/16mm.


Grade 8 will do, I would get washer for each side as the stock bolt has a FLANGE HEAD, which is like having a "built in washer" I would also get locking nut/washer as well. The ones I use are called deformed locking nuts.

The following is for the front and rear LOWER control arms axle side and frame side and both sides of the track bar (axle and frame). I haven't gotten to the uppers just yet. If anyone had time to look at those well that be awesome if not, I'll get to them after Christmas. The shock and sway bars ( sway bar only applies to some aftermarket kits. Example I the sway bar links that my teraflex 3 inch lift came with use the wrong bolts. All shocks need changing as well as they are not shoulder bolts.

MAKE SURE THE BOLTS ARE FINE THREAD (UNF) !!!
  • 8) 9/16-18 UNF x 4.0" long (LCAs)
  • (4) 9/16-18 UNF x 3.0" long (TBs)
  • (12) 9/16-18 UNF lock nuts
  • (24) 9/16" Extra Thick hardened flat washers
Where is everyone sourcing these new bolts?

Rick.
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Old 12-21-2011, 05:26 AM
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Wow! Thanks for the info, must be another corner cut by jeep....
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