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Differential failure due to one wheel locking up

Tiny
TUNNELMAYNIA
  • MEMBER
  • 2006 FORD F-450
  • 6.0L
  • V8
  • TURBO
  • 2WD
  • AUTOMATIC
  • 144,000 MILES
Upon going to pick up my truck (description listed above) after having the differential replaced (what was assumed as general wear) the shop was test driving the truck and it was still binding. They put if back in the air and put the truck in gear and the right side bound up. They assumed it was the rear end again but when I looked under the truck I saw a gap between the rotor and hub. They pulled the wheels and sure enough there was a gap. They pulled the axle and hub assembly to find the parking brake and rotor bolts had come loose and only three were loosely holding the rotor to the hub. The rotors were new and installed by this same shop only three to four months prior to this. The bolts chewed up the parking brake pads, cable, and mounting block for the pads. The pads came loose and were getting stuck against the mounting plate along with bolts working their way out of the hub that held the rotor on (only three left loosely holding the rotor to the hub). The flange were the bolts go through the rotor is even cracking out from stress. I am assuming this caused a bad shock to the drive train and may have even locked up the right side momentarily at speed. Would the wheel locking up at speed damage the spider gears in the differential (break teeth off the gears, crushed/blown out shims from behind gears, bend or gouge the gear shafts)? Would one wheel locking up cause the other wheel to increase in speed, but without the wheel actually being able to speed up (rolling at a constant speed and drive shaft turning at constant speed) would the shock be absorbed by the spider gears to were failure would occur in the differential? Please help me with these questions. I feel that all of this was caused by someone not tightening the bolts down to the required torque specs and using some loc-tite as an added safety. The shop is trying to skirt all responsibility for this. In all there is a re-manufactured differential in it from Weller truck parts, fourteen quarts synthetic gear oil, and now it is looking at a new hub (all bolt holes ruined), bearings, seals, parking brake cable, brake mounting plate, rotor, disc brake pads, parking brake pads, parking brake return spring.
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Tuesday, April 11th, 2017 AT 10:45 AM

4 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,480 POSTS
It sounds like the rotors were not installed properly when they were replaced. They should not come loose on their own. The catch is, can it be proven that the shop is at fault?

As for the damages caused if those parts all get tangled up at anything over a walking speed. I would expect to see major internal damage to the differential and maybe even a twisted axle or housing. There is a lot of inertial force in those parts.

It is different if you were to climb on the brakes and lock up the rears. In that case you are slowing/stopping both sides the same amount and you will probably not have your foot on the gas. So although the system would get a hard shock, it would be spread through the parts and not cause any real damage other than flat spotted tires and maybe needing the seat cleaned.

Your thinking is correct as to why the parts are damaged. If one side suddenly locked up, Something is going to break.

As for the shop, If it were me I would tell them I plan on never using them again, and that I will be sure to tell others who go there how they treated me.
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Tuesday, April 11th, 2017 AT 2:33 PM
Tiny
TUNNELMAYNIA
  • MEMBER
  • 3 POSTS
I have pictures of the rotor and brake shoes. The main brake friction area of the rotor looks brand new still. No worn grooves or lips along the edges. The bolts were rattling out as far as I can tell. The bolts are not sheered off and most of them are straight. The few left holing it on are backed about half way out and bent over from impacting the shoes when the shoes bound up against the back brake mounting plate. The bearing seals also appear to be shot from shrapnel damage. There is one other thing bugging me and that is the fact there's no sign of loc-tite on the bolts or in the bolt holes of the hub. So what you mean by the gears being damaged is they are not designed to go from no rotation and minimal load to the full drive force being transferred in a split second to one gear? The axle shafts in this truck are very large in diameter and appear to be a much more solid price of the puzzle then the spider gears which seam small and more vulnerable to breakage.
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Tuesday, April 11th, 2017 AT 2:59 PM
Tiny
TUNNELMAYNIA
  • MEMBER
  • 3 POSTS
Here are the photos.
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Tuesday, April 11th, 2017 AT 9:25 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,480 POSTS
That is not nice to see. No, the gears in that unit are designed to handle the loads that vehicle can pull/haul, not the instant shock loading equivalent to many times that amount that locking one axle would apply to the gears.
Those gears only mesh with two teeth or so and they were trying to instantly stop over 300,000 pounds of kinetic energy (depending on road speed at the instant the brakes hit and the subsequent impacts) at 50 mph stopping a vehicle in four feet generates around thirty G's of energy. In your case it was trying to stop a single axle instantly so the loading would be much higher.
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Wednesday, April 12th, 2017 AT 12:38 AM

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