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i drive boats
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117 Posts
Discussion Starter #1




top mount snapped, bottom mount weld broke and the threads slipped out. driving about 15 mph in the pouring rain. no idea why it let go at that time.
 

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Haters Gonna Hate
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5,869 Posts
what brand of bars are those? looks to me like they are pretty poorly built and someone got in a rush and didn't get a good bead laid on there..... sorry for your luck
 

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StackinChipsLikePringles
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Its been broke like that for a while
 

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Its been broke like that for a while
x2.looks as though the tube adapter has just been sitting in the tube for a while,plus the rod end is rather rusty along the break.my guess is internal corrosion got the best of the weld and the other rod end broke from taking the brunt of the load.what i find odd is rod ends dont normally break that way unless subjected to a shear load.
 

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Newbie
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401 Posts
With the top bar being mounted to the center of the axle will cause a shearing force. Top tension and bottom compression from axle wrap.
 

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Have you the OP talked to Fabtech yet?
 

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Administrator
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When I found my Fabtechs on Craig's list they had all new hardware the seller had issues with his brackets so Fabtech had already improved them with gussets and sent him the updated version

mine have done well so far but seeing that makes me cringe

definitely contact them
 

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With the top bar being mounted to the center of the axle will cause a shearing force. Top tension and bottom compression from axle wrap.
no,unless the rod end seizes it can rotate in the up-down and even side to side motion(within 20*give or take).shearing is a 90* force.i dont think it broke from shear load,but rather from an impacting stretch.the fault all lies in the lower tube adapter weld being sh it whether from corrosion internally or just plain not welded good.fabtech should pony up a new set according to their warranty.
http://www.fabtechmotorsports.com/policies.php
 

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Yes, more so with the rod end freezing.
The axle will warp and the spring will go into an S, so the center moves. Either if it is forward or back it will causing a shear. It is loading that one side of the rod end and can cause it to bind so it wont move, more so if it is pre-loaded at all.
With the top in the middle of the axle has no help in axle wrap. If you dont believe me unbolt the bottom bar and go for a ride.
Make a fist in front of your face and rotate your hand like the axle rotating.Top will be in tension and the bottom in compression. It will rotate around the middle, which will causing a shearing force on anything attached to it. I dont see impacting occurring in the middle of the axle, not like the bottom.
It has been a while since I have done dynamics but that is what I see occurring.
 

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the impact is from the bottom rod end being loose and the slamming against the tube when torque is applied.hold your fist 3 inchs from your face and then slam it into your face,thats impact compression.the top rod end was given an opposite stretch impact every time that happened.im not arguing the theory,but more the label.which of these pictures do you think is shear strength and which is tensile?

to the op:call fabtech,they have a limited lifetime warranty on workmanship and defects.
 

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i drive boats
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117 Posts
Discussion Starter #16
i was not the original buyer so im pretty sure i wont be helped. i brought it to a fabtech dealer and he ordered the replacement rod, and is going to weld the other tube.
countless 12s passes on 37s probably didnt help
 

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Newbie
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401 Posts
Alright smart ass. I know the difference in shearing and tension being an ME. I dont see how the middle of the axle will cause an impact being that is the rotation. The bottom or top yes it can if it slams it. If you dont think anything mounted to the middle of the axle will not shear off unbolt your bottom bar and drive. The axle will still rotate till it gets to the point the bar goes into tension. It might cause a shear and impact, but I think the shear is what is going to break it. If the top bar was mounted to the top only the I agree the tension is what broke it, but not in the middle with no other support.
Hiem joints are great, but you can still load one side of them with a force and they dont rotate that freely, more so if they are cheap ones. Pre-load the top bar so that it is pulling back and with the lower bar not loaded the axle will slam the bottom into compression and the top one will try and rotate. Even if it is a little, if it cant rotate something will give sooner or later.
 

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Here is my reasoning, feel free to say this is wrong.
This is the reason that OUO and PMF bars are either just on the bottom of the axle or one on top and bottom.
When you hammer the truck and the axle tries to wrap.
A force is applied to the bars, no matter what angle they are at, that force is split into right angles, one forward and one up. Now the upward force is going to depend on the angle of the bars. Most I have seen depending on the lift o fhte truck is pretty close the angle of the driveline.
Now if you have the bar mounted in the middle it will not have a force applied forward only up because the axle is rotating at the point and not moving.
Now if you look at OUO and PMF bars that mount on top and bottom.

Jueff is right, the OUO or PMF are a better design, but costly.
The bottom is the same as above, the top one depending on if it is at a angle or not could be just a force in one direction, which would be back.
 

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i drive boats
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117 Posts
Discussion Starter #20
got the broken one fixed, and noticed the weld cracked through the axel on the driver side and was leaking gear oil when on a hill leaning to the left.
8 hours after i installed the passenger on back on, and about 40 miles, it broke the mounts off the axel.
PMing PMF right now.
 
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