Violent shakes in when warmed up

[Heinri_k]

1989 Comanche. 4.0 inline and AX15 tied in with NP231. 

When I begin my drive, everything is good and functional just fine. The issue only ever Begins after about 20 minutes or more of driving. The issue only occurs when I am either at a dead stop in first or attempting to reverse from a stop. Basically when I let the clutch out and give it gas, the truck jerks violently. It goes away if I give it more gas and pull away, then it shifts just fine through 2nd, 3rd, ect. The jerking feels* like it comes from the rear and some tires I can hear the tires chirp a bit depending on what surface I'm on. 

I have read a lot on this and I'm thinking either my clutch is going out or my rear main is leaking and causing this. I check my oil frequently and the level doesn't seem to move, but I have noticed small drops of oil on the transmission mount that I can dab up with my finger occasionally. As far as it being the clutch going out, would it not do this cold too? 

 

Additionally, to add for general input. I have a Novak transmission mount recently installed and I have checked the motor mounts. I do not believe this to be a mounting issue. Secondly, I have not yet had a chance to check the transmission fluid or the transfer case fluid. Though I do have plans to change them soon. I do not think they would be the cause for this. My clutch adjustment seems to be fine. And I do not believe this to be a driveshaft issue, but I did recently change my rear leaf springs with factory height. It's had a 3inch front spring lift since I purchased it.

 

Any input is very much appreciated.