Perhaps they're old and the crush sleeve has let them loosen up?

I'm no expert but perhaps a set of Yukon gears and a solid collar are the answer? Plus a good quality install.

 

That may be the best possibilty I have heard yet. I was thinking yota just dosent use a good enough material for there gears to handle what I put my 4runner through.
Time for a SAS!

 

Spend some time studying the site I linked to above. You can learn a ton. #1 is to have a real pro install your gears! Hopefully Zuk will chime in here at some point with the right questions and some actual knowledgeable answers.

 

i would say its the locker in the rear because in theory a locker in the rear will all most lock the whole system because 4wd is diagonally split. ie when im stuck my left front and right rear will spin if i locked the rear the front would stop spinning too because theres no center diff in the case like awd. so the locker in the rear sounds like it would put a huge ammount of stress on the front drive line but i would still gues the cv to let loose first.

but if im wrong feel free to correct me im just a kid and want to learn

 

I would expect the tiny stub axles to twist off before the relatively stout 7.5" IFS front gears exploded....I say relative because while it is only 7.5" it also has extremely well captured carrier bearings. The carrier bearings are recessed in the carrier....it's not like the Toyota 8" that has the external towers that might sway just a tiny bit.
If the carrier bearing pre-load is set high on the IFS front then ring gear deflections should be very small indeed. And that contributes greatly to the over-all strength. On a used front IFS carrier, the CBPL might have disappeared over time....or if a gear installer set them up they might not have used as thick a carrier bearing shim as could have been used to get good CBPL.
A lose pinion could also cause a breakage because under high torque loads the pinion would shift out of alignment and the contact pattern would wonder off the ring gear tooth and POW!
Also, there is no solid collar available for the front IFS....yet. The crush sleeves seem to work well in the front end application.
Perhaps cryo treated bearings and cryo r/p with a nice pro install is the E-ticket? ZUK

 

I'm sorry - that has to be the most ridiculous thing I've ever heard. Each axle's diff works independently - there is NO correlation about which wheel will spin depending on what the other axle is doing. Power goes to the wheel with the least traction - PERIOD.

What you are probably seeing in your truck is that with the rear locked, you start moving and ease up on the throttle. When an open diff spins a wheel, it spins at 2x the normal speed. A locker keeps that to 1x (same as) normal speed for the axle the locker is installed in.

 

http://auto.howstuffworks.com/differential.htm

 

And I bet it's starting to get hot in AZ so dude, wtf are you waiting for?

Definitely a set of cryo'd gears and a zuk install will get you back on track.

Don't forget to send in a pack of razors for the cryo treatment as well.

 

Dont know about AZ, but its definatly getting hot in Utah. And whats the deal with a pack of razors?

 

They supposedly last a lot longer if cryo'd.

 

http://www.gearinstalls.com/bobby/bob18.jpg