Traction Bar Setup Frustrations

ARbowhunter7

ARbowhunter7

Opulence...I Has It.
Joined
Sep 8, 2007
Messages
1,370
Happy Labor Day, guys.
I've been having an issue with my trac bar setup that has baffled me for some time, and has occurred with multiple sets of bars (two CPP sets and a custom set, in lengths from high 70's to mid 80's) . Rear attachment points are bottom-U-Bolt brackets and front points have been both thru-frame bolt brackets and the over-the-frame U-bolt style.
No matter how much preload I set, or how tight I get the jam nuts, they quickly loosen up and start rattling like a SOB (and not doing their job). I've scribed a mark on the frame to make sure it's not the front bracket sliding under load, so I've narrowed the problem to the rear.
It almost seems like the load on the rear u-bolts is shifting the rear axle downward, throwing my pinion angle way off and putting an S-curve in my leaf pack. I'm out on the pipeline, so I won't be able to accurately check my driveshaft and pinion angle until I get back home to my shop/tools. What is the likelihood of this being the culprit? Anything else that I'm overlooking?
Thanks in advance.



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I'm here to read but... Holy Jesus!!! Talk about a ghost around these parts!!
 
BRE said:
I'm here to read but... Holy Jesus!!! Talk about a ghost around these parts!!
Click to expand...


Hey, Bud! Work's been crazy lately, so time to mess with my truck (or even talk about messing with my truck) is rare. I'll be back at it soon, though!

Disturbed, this problem still occurs even when my preload is set just so the bars are barely snug. 10 minutes of "spirited" driving (to induce axle wrap) and the bars are rattling around again, with the jam nuts still tight at both ends.


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Try putting a tack weld on the jam nuts after resetting to the desired preload and observe for any other variable
 
Hurley said:
Try putting a tack weld on the jam nuts after resetting to the desired preload and observe for any other variable
Click to expand...


That I can do! I've got a Lincoln Vantage 500 that has been in my way all day...I'll fire her up at lunch and tack those jam nuts....I'll probably go ahead and run a bead on the front bar mounting brackets, just to be 100% sure they aren't moving.
Will report back.


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It really seems like the issue is in the truck not the bars. reset them and put a gopro under the truck to see what's going on. Any weird vibrations in the truck?
 
Can you get us some pictures of your setup so we can see what you're working with?

(P.S. Not that setup you perverts...)
 
if you've got u bolts going over the axles it will always slip them. no way they will ever get tight enough. bolt the bar to the btm of the ubolt plate that holds the axle and it wont do it anymore. we fab brkts and weld em on the rear axle.

yeah man where the heaven you been...figured ya quit
 
dieselbeef said:
if you've got u bolts going over the axles it will always slip them. no way they will ever get tight enough...


yeah man where the heaven you been...figured ya quit
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Haha, nope...I'm still in it, bud!

And here is a quick shot of the rear axle bracket (Don't judge me based on the dirt...she's been out on the pipeline for a couple months straight without a bath).
44733d0a2d63359ac927dafe6807b203.jpg


Disturbed, yes I do have some driveline vibration (under load) that started recently. All u-joints, carrier bearing, etc. are new, and the truck rides smooth as glass otherwise, so I'm thinking you're onto something.

I also reset the bars to snug and tacked the jam nuts in place, drove for 1/2 hour and sure enough, I hit the highway and heard the clunk of loose bars on the locked 2-3 & 3-4 shift. I also could hear them rattling when going over expansion joints on the road.

I wonder if the u-bolts have slipped, and the rear axle is now set with the pinion down a few degrees, and every time I reset the bars it rotates the axle down further, causing the driveline vibration Disturbed pointed out?



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The perch that the rear block sets on is not movable unless it's broke. You would see signs of it moving like rust or something where its moving metal on metal. Now if you look close at the top of the perch and the bottom of the block you see some discoloration other then the dirt which in my opinion looks like its been moving. You might just loosen the bottom nuts of you u bolts and see if you can put a wrench on the top nuts and see if maybe the bolts have stretched any. Wouldn't take much.
 
DISTURBED said:
The perch that the rear block sets on is not movable unless it's broke. You would see signs of it moving like rust or something where its moving metal on metal. Now if you look close at the top of the perch and the bottom of the block you see some discoloration other then the dirt which in my opinion looks like its been moving. You might just loosen the bottom nuts of you u bolts and see if you can put a wrench on the top nuts and see if maybe the bolts have stretched any. Wouldn't take much.
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It does look like that block has been moving around, been battling the same issue with my 97 F-350. That still doesn't explain his pinion continuously rotating downward but could explain the vibration. I'd for sure loosen the bottom nut and try to tighten up the u-bolts for starters. Unless the tubes are slipping in the housing? That's the only thing I could think of that would let the pinion slide downward and would also cause the bars to loosen up I suppose.
 
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What does the view of the bolts look like parallel to the axle? That's a lot of force on what are already long bolts.

Is the bracket on the underside of the tube welded on? If not, weld it.
 
Update: I finally was able to get an accurate read of my pinion angle, and it was over 7°, which is 3° off from when I did the initial setup/preload on the bars. I corrected the pinion angle, and will weld the rear brackets to the axle tube to keep them from slipping.
Thanks for all your help, guys.


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But WHY did it change? I'd be welding the axle tubes to the center section too.
 
JWhite said:
But WHY did it change? I'd be welding the axle tubes to the center section too.
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I believe the u-bolts either stretched, or simply didn't have enough strength to handle the pressure put on the brackets, but I'm still not sure why that would cause the pinion angle to be INCREASED. I would think the brackets slipping at WOT would allow the axle to rotate slightly inside the brackets, which causes the pinion to rise, creating a pinion angle closer to zero, not further.


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