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Discussion Starter #1
I thought I would share this information on what can happen on mis-match tires on a 4x4.
A diesel 4x4 truck came in today on the hook with a catastrophic transfer case failure.
The truck had near new tires on the front while the back tires were bald. The front tires were spinning slower than the rear due to the tread depth difference front to rear.
The torsional wind up stress on the transfer case had to be tremendous. When the nose of the case broke off the front driveshaft almost went through the drivers floor board. I can't imagine what that would have sounded or felt like!
Good example of how important on a 4x4 that all tires are the same circumference.

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What make/ model of truck? What type of transfer case? Was the guy driving in 4wd on the road all the time?

This seems like there's more than tire wear at fault. The difference in circumference caused by even a half inch of tread wear shouldn't do that. I've known guys to run close but not exact gear ratios after doing axle swaps (4.10 in one and 4.11 in the other) and even that difference didn't cause catastrophic failure.

Full time AWD vehicles like our Subaru, it's a bigger concern.

In any case, wow! That's definitely a catastrophic failure.
 

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I know the newer Rams (2003 and newer?) use non-selectable/solid front hubs so the front axle is always turning. But I had thought they disconnected the front driveshaft within the transfer case when in 2wd even though the front driveshaft stills turns while driving?
 

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Discussion Starter #5
I know the newer Rams (2003 and newer?) use non-selectable/solid front hubs so the front axle is always turning. But I had thought they disconnected the front driveshaft within the transfer case when in 2wd even though the front driveshaft stills turns while driving?
That is my understanding also. The truck was from out of state, I suspect the continuos heat buildup at interstate speeds and couldn't take it anymore.


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Perhaps it was in 4wd?
 

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Discussion Starter #8
I have seen a similar incident on an older AWD explorer that had oddball tires front to rear.


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My thought also,,, running in 4wd on drive surface... You can do that going straight for a mile or so ,but for any length of time , asking for trouble.
 
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Discussion Starter #10
Just thinking about it, I suppose a bad rear joint on that front shaft could have contributed . That would have been a lot of vibration to tear the nose off the transfer case! There's not enough evidence left to decipher that, lol


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My thought also,,, running in 4wd on drive surface... You can do that going straight for a mile or so ,but for any length of time , asking for trouble.
Ditto that, and a company truck some drivers could careless. The roads are clear also.


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Ditto that, and a company truck some drivers could careless. The roads are clear also.


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You know how to fix a strange noise on a company truck? Turn up the radio. :laugh:

I work on a lot of company owned, employee operated equipment. The way things break in that environment used to surprise me but now...yeah. Some people...:nunu:
 

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Discussion Starter #13
You know how to fix a strange noise on a company truck? Turn up the radio. :laugh:

I work on a lot of company owned, employee operated equipment. The way things break in that environment used to surprise me but now...yeah. Some people...:nunu:
You hit that right on the head!! It's mind numbing some of these failures on company vehicle with multiple drivers. They get pounded in the ground!


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To my understanding rolling down the interstate in 4x4, 2008 dodge 3500


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On these trucks 4WD engaged and asphalt doesn't work...even with 100% matching tide diameter it doesn't work. The front axle and the rear axle will not be geared exactly the same and thus the truck needs to be on a surface that will allow some slip.

It is amazing the driver could not tell as even the slightest of turns would make the truck bind, grab and drive differently.
 

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Discussion Starter #15
On these trucks 4WD engaged and asphalt doesn't work...even with 100% matching tide diameter it doesn't work. The front axle and the rear axle will not be geared exactly the same and thus the truck needs to be on a surface that will allow some slip.

It is amazing the driver could not tell as even the slightest of turns would make the truck bind, grab and drive differently.
Right, not to good rollin down the road on dry pavement locked in, let alone tires with different diameter amplifying the situation.

As 56FordGuy said probably just turned the radio up and thought turning with the truck jumping around in 4x4 was humorous.

I have on occasion been driving on bad roads locked in and park in the garage. Next day roads are cleared and got a few miles down the road before I realize I'm still in 4x4. But never more than a few miles...


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FYI. Stupid cannot be fixed. $,02
 

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My favoritie personal experience with employee operated 4WD-

I worked for a cellular service provider back in the 90's. We had to drive between sites during our shift. It was about approximately 20-25 miles, mostly highway. Our pool vehicle was a Ford Explorer. I came on shift and the previous tech said something was wrong with the Explorer. She said that she could not get it up to highway speed. I asked if it was in 4WD. She said that it had started snowing (mind you, we never had accumulation that night) so she put it in 4WD. I went out to the vehicle and it was in 4WD LOW. She had gone more than 20 miles, trying to achieve highway speeds on wet, but not snow covered, pavement. I wonder how many miles of life expectency she took from that drivetrain that night?
 

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All this is probably why a lot of the newer vehicles kick 4X4 out at 20-40 mph.
I like CyberShanks comment "Stupid cannot be fixed".
 
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I suspect there is more to this then mismatched tires had to be running in 4 wheel. I guess I might have to rethink fixing the indicator light that tells if your in 4 wheel. It seems inop 4 wheel drive indicator light is common on dodges. I'm pretty sure I can remember to take it out of 4 wheel but then again according to the wife I don't hear much or remember anything.
 

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Could have also been a u-joint letting go. At hwy speed that driveshaft will have a lot of energy with trying to beat things to death.
 
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