High Pitched Whir from Front Diff When Engaged

[drcomanche]

As the title states, there is a high pitch hum that gets louder as the vehicle goes faster, but only if 4wd is engaged. It makes me feel like it's going to blow, but it has diff fluid. I have my front axle in pieces, so now I just need a hint on what needs to be replaced.

[AeroNautical]

Bearings maybe? Though if it were the bearings, it would probably make the noise even in 2wd. Are you sure it's not the t-case?

[drcomanche]

I've had the tcase engaged before without being in 4wd(low gear is nice for gravel hills) but never heard the sound then.

[Eagle]

I've had the tcase engaged before without being in 4wd(low gear is nice for gravel hills) but never heard the sound then.

That's not possible. Your options are 2WD-High, 4WD-High, and 4WD-Low. There is no 2WD-Low available.

 

Are you certain the whine is from the front differential and not from the transfer case? My first thought is that you're hearing the drive chain.

[drcomanche]

I probably should have specified that I have modified axles that require being locked out to engage them (D44 Front). Otherwise, the driveshaft just rotates freely. 

[Blue XJ]

Even with the hubs unlocked, everything in the front axle will still spin if your in 4x4, it just won't be under load since it isn't 'connected' at the wheel. 

 

I would look into bearings in the front axle.