During our last snow storm yesterday, the guys called me and said that Smokie was making a God awful nouse and said they thought it would blow up. After my heart palpitations stopped, I tried diagnosing over the phone. Turns out when 4wd and hubs are disengaged, noise goes away. Great! Just a bad u jount... Have them swing into the local shop I buy my business fuel from to see if it can be swapped quick. Mechanic jacks up the front and declares that the front diff is most likely seized up. Now, I'm under the impression that the front diff allows one tire to spin faster than the other during a turn. How does the front diff play into the 4wd? Please explain if this is possible, or if I should go back to looking for a bad u joint. I haven't had a chance to look at it yet. We just finished cleaning our lots at 3:30 THIS afternoon. We broke 3 trucks in 1 storm. Ugh.

 

I'd get to looking. A diff can seize, but diagnosis would require more than quick look to rule other likely culprits.

 

The front diff comes into play in 4x4 if you want to turn. The outside wheel needs to spin faster than the inside wheel in a turn, and the diff is what allows that to happen. Even if you are going straight the diff needs to turn with the front axles. It is very possible that the diff has seized. When was the last time the fluid was checked or serviced?

Many people think that in 4x4 all the wheels are locked to spin at the same rate. That's not true. Some trucks have a limited slip in the rear, but NO truck has one with a limited slip in the front from the factory. You could easily find a condition with limited slip where you could not turn. No truck maker is going to sell a truck that won't turn some of the time.

 

Thanks for the replies guys! Here's the update. Took the truck to a local shop that does good work, but is expensive. Not complaining about it, just can't afford to go there often, lol. The front diff was seized. A buddy if mine had a spare front Dana 60 with 3.73 gears that he sold me for $500. Had newer u joints and ball joints in it, and one good wheel assembly too. The shop told me why it froze. I have some knobby tires on the truck for snow. They were pretty low on tread, but not awful. At the beginning of this season, I put 2 new ones on the back and the 2 best used ones on the front. The mechanic measured, and the new tires have a greater circumference of 2". When the truck was in 4wd we were killing the front diff. So keep that in mind when buying tires, esp. If you have aggressive tread. As of now, the truck is all set, just have to go buy 2 new tires for the front.

 

Yup. You bring up a good rule for the new four-wheel-drive folks to learn:

Not only must the front and rear differential gear ratios be the same, all four tires must be the same circumference. That doesn't necessarily mean they have to be the same size tires, but during one revolution, each one must travel the same distance. Otherwise, binding occurs, which does the damage.

Never be in 4WD on dry asphalt or concrete! Since nothing is perfect, some binding will occur any time you're in four-wheel-drive. The binding must be relieved (or you break stuff), which is why you won't have problems on a dirt, muddy, wet, or icy road, but you will on dry asphalt or concrete.

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