Now that I have swapped the rear end from my friends totalled 4 runner into my pick-up, As I was changing it over, I was counting the teeth on the gears, and they are not the smae, Does this mean I am going to have to change the front diff as well? To match up the gearing for when im in 4 wheel drive? Is that a very hard task to accomplish?

 

Oh yes, the front a rear gear ratios absolutely have to the same.
The front is a different process to swap out than the rears, but it's not any harder to do. (Okay, it's harder to do, but it's not any more complicated...)

 

Yes!! Definetely true... this needs to be done as well

 

I am just wondering for my own knowledge...if the main gears aren't the same, does that mean the gearing is automatically different? Is it possible that the pinion gear is different and you still get the same gearing? I am just asking, because on my 3rd gen the front diff is smaller and I am wondering if that's even a possiblity.

Sorry if I am hijacking here a little bit. You should definately have the same gearing up front and up rear.

 

I dont know, but:

It is possible that the ring gear could be different, and the pinion will make up for it, but its very much not likely when looking at simiar axles (such as a typical toyota 8" and 7.5")

 

The size difference between the 2 differentials is different but the gear ratios will be and have to be the same, otherwise the drivetrain will bind in 4 wheel drive