2001 4 x 4 tacoma front wheel fell off. Looks

You'll need to extract the end the axle shaft from the hub bearing. There is not enough play in the axle shaft to allow this without at least partially removing the front strut assembly. Sometimes just separating the lower ball joint will allow the strut/spring to move enough to work the spline out the bearing. Once you've done that, then you must "pop" the inner CV joint out of the transaxle. It is installed with a snap ring to hold it in place. This process can be tricky and you can damage the CV joint or the transaxle case if you don't exercise caution while doing this. Be careful not to pull outward on the axle shaft...this will not release the inner joint and will most likely cause the inner joint to separate, making removal more difficult.

check your cv joints which are part of the front wheel drive shafts probably need replacement

possibly a separated tire or a wheel weight fell off causing the balance to be out

When you put the vehicle in drive with your foot on the brake, and you hear a clunk. You may have a bad CV joint or axle. If not it may be a bad wheel bearing. Those would be the first two I'd Check. Outside of that sometimes poor wheel balancing or a tire belt separation. Either way it should be looked at before you hit 75+ mph. I had a Honda that I had just got off the highway with my wife and 3 month old daughter in the car. On a side street pulling away from a stop sign. The right CV shaft let go and dropped the wheel on the ground. There wasn't as much as a shimmy or a groan prior to that. If we had stayed on the highway another five minutes, I can only imagine. Please check it out for your own safety.

Has the transfer case ever been serviced? The fluid should be changed every 30,000 miles, if not the works can stick and cause engagement problems. Make sure the vacuum to the front hubs is available, if the front hubs are not locking the front drive shaft will turn but no Front wheel lock up and no 4 wheel drive is available.

if it sounds like the squeek is every revolution,the joint will need replaced.

You need to check the cv joints in the front end or the u joints in the front drive shaft.If none of the above then the problem is internal in the front diff.

You need to check your drive shaft universal joints. Chock your wheels so the truck can not move or roll. Take It out of gear and grab the drive shaft and try to turn it by hand, looking at the rear joint as you do this, then do the same for the front joint. You are looking for the shaft to move and not the rear or front yoke, if you have a loose feeling that is your U-joint.

Sounds like one of your hubs is sticking and not engaging. You can check them by engaging the hubs and the transfer case and jacking up each front wheel independently if it doesn't spin your good, if it does you found your problem. As far as fixing a hub goes, it may be just dry and need some grease, or there are some very good aftermarket hubs available from Warn.
Hope this helps

Without looking at it, you may have one or more of the following:

Rust on the inside edge of the rotor (most common)

Worn front brake pads

Front wheel bearing problem.

Backing plate (behind rotor) rubbing the rotor

These are the most common causes, you can see 1,2 & 4 with the wheel off.

Hope this helps.