I've been trying to figure out why there is a chirp and vibration coming from my T-case that changes speed the faster I go. It never happens when I have the front hubs unlocked and the T-case in 2WD but in any other configuration where there are front drive components moving there is noise and vibration. 4WD with the hubs locked is the worst.
This is the first 4X4 I've owned so I am new to the issues it might have. I'm thinking there is something wrong with the T-case like a bearing or linkage so I would have to get into that later, but I'm wondering if this could be a symptom of a bent axle or a imbalanced front drive shaft or a broken spider gear, ect.
I also don't know how to tell if an axle is bent. This truck has had a hard and abusive life before it came to me so it could be multiple problems.
If this is a repeat post, point me to a good tread and I'll gladly remove this one.

Just for kicks, here is a pic of it from last year when I got it.

 

Drain your transfer case and fill it with Mobil 1 gear oil and B&G brand additive or any other good brand of additive (GM, etc.). Drive the truck for awhile (use 4WD as much as possible) but if the noise and vibration are still there you could have a front drive shaft problem (famous for this) or a front differential problem. The gear type cases are pretty beefy but if the front drive shaft is bad it could have effected the transfer case bearing where the drive shaft connects onto.

 

I forgot to mention that I just changed all of the drive train fluids with Pennzoil Synthetic 75W-90 (it's what my shop uses). Would Mobil 1 and an additive really make a difference? I'll try to get the truck on a lift today and take a good look at the front drive shaft.

 

Yep, the front driveshaft u-joints are shot. I guess I'll start there.
Thanks for the input. I'll let you know how it goes.

 

The Pennzoil should be fine just install a good additive.

 

I took my front drive shaft to GTF and they said that it was too much play in the splines so they couldn't used it. They built me a drive shaft from a new Toyota but I need to either drill out the flange bolt holes on the t-case and the diff because the yokes are different, or I can replace the flanges with the Trail Gear adapters I got. What would be better? I was going to just replace them myself but I can't seem to find the preload specs or what kind of parts I would need to replace. Is there a good thread that I'm just not finding that goes over this? I might just take it back to GTF and have them put it on.

 

Another anchorage person, cool! GTF alerted me...

 

I replaced my flanges when I did my drive line work, granted it's from going to dual cases, but the concept is the same. Just remove the flange nut remove the flange, and install the new one, I believe the nut gets torqued to 90 foot lbs, ill check my fsm when I get home from work. I've also heard from many reputable sources, that the flange nut should be replaced, since its already been staked its weaker and can work loose