unusual sound from drive train

[Johns02ranger4x4]

Have 2001 Ranger 4x4. When the 4wd is not engaged the drive train runs like a champ and is quiet. However, when the 4wd (hi or lo) is engaged the drive train acts and feels like it is straining to run, and I think I can here the transfer case chains moving. If I turn, the 4wd will quiet down and I feel no strain on the drive train, the noise disappears and it runs smooth. 5 seconds later, after the truck has straightened out the noise and strain return.

Looking for help guys. Let me know if you know what this is or whats causing the problem.

JC

 

[fr7]

Have you checked your CV axles? It's weird that it doesn't do it while you're turning, usually things tend to bind and make noises when you turn the wheels while in 4wd, special on dry surfaces..

 

[4x4junkie]

That sounds like maybe your axle gear ratios do not match front & rear (the rear having a deeper (or higher numerically) ratio than the front). Perhaps a previous owner swapped one of the axles with a junkyard unit while not paying attention to the ratio the other axle has.

So when you're in a turn, the front axle moving faster lowers the amount of binding between both axles, and then when you straighten out (and all 4 tires are trying to travel at the same speed), the differing ratios creates the bind again.