pulling out problems when releasing clutch

when i pull out in the level it doesnt really to anything but if the ground is alittle up hill and not much up hill either and when i release the clutch and go to pull out the whole frontend shakes and jumps up and down alot .
i have and ideal what this is but i want to know what you think . and the truck has 17,000 miles and the rear main seal seams to be leaking alittle but not much . and it seems to me that the clutch is real easy to push in with my foot . and it seams to act worse the more i rev the engine when i pull out .

Mine was oil on the clutch, rear main leaking, and "soft" engine mounts. The mounts were spongy from age and oil soaked. Shook like crazy with both those problems.

Clutch grabbing and shaking is often due to bad/broken mounts, on eng and /or trans. Also ck the 2 studs in the bottom back of trans. that hold it to the mount, these like to get loose in the trans. case. oil on the clutch disc can cause a prob. too but it usually takes a really bad leak to get in onto the disc.