4wd not working properly on 97 Toyota tacoma

Recently my Tacoma 4wd isn’t working properly. It goes into 4wd but if I go forward a few feet it feels like the drive shafts are fighting each other. I put my truck up on jacks and I made it roll and my front end shakes. Any ideas what it could be? If you know what the problem could be it would be really appreciated. Thank you.

 

are you trying to operate it on dry pavement?

 

No. It started to act up when I took it to the beach. I had to 2wd it out

 

put on jackstands

put in 4wd, put in N

--drop rear driveshaft--

hows the front acting when you spin front wheels ?

 

Has the rear been re-geared? Front and rear diffs have to be same ratio.

I would start with this:

Good idea