A skipping feeling when the truck is lugged down

Hey guys new to the site. I have a 2001 Tacoma 4cyl 5speed and when the truck is in 3rd 4th and 5th and starts to lug down a little bit I start to get a slipping or skipping feeling that feels like it's coming from rear of the truck. I'm wondering if it's a rear end issue or transfer case issue thanks.

 

cluch slipping?

 

The clutch seems fine it seems like coming towards the rear of the truck

 

Almost like the rear end is slipping but not sure and hope not

 

So, you're sure it's from the rear end? I know that, in hot weather, high load and low rpm can make the engine diesel and stutter. (which is solved with higher octane gas, in case you care)

 

Yes Rpms stay put it's not the engine chocking it seems like it's coming from the rear