I just installed a new Adams driveshaft, but it's 100% compressed. There's no spline showing, I had to jack up the front end just to install it. There has to be a problem with this, if so how severe is it?

 

It sounds like the DS you have is too long. Typically DS manufacturers will ask you to supply a proper measurement for your specific application. If you buy something off the shelf, this is the risk you run. If you have no room to compress the DS, that is kinda a big deal.

 

Get that thing out of there or it will beat your TCase to death by pushing on the output yoke from the front of the TCase. How did that happen as, per Resharp's response, they should ask you for yoke face to yoke face meaurements with the Jeep on its wheels on the ground.

 

Do you have a lift? When you installed it, did it have any travel at all? or was is solidly compressed for you to install it? Sometime's they cram it full of grease and it may appear fully compressed just have to push harder to get that grease to move. If it is fully compressed like Sixty mentioned, it will beat or even break the t-case in half if you slam the suspension hard enough.