What do I need to do to get to the freeze plugs on the back of the motor???

 

Are you talking about the freeze plugs that are under the rear cylinders, or the plugs that are behind the flex plate on the very rear of the engine?

If you are talking about the plugs on under the rear cylinders then you will spend a bit of time under the vehicle, you can try and knock them in a bit so you can grab the lip and pull them out. Depending on the space available or lack thereof you might have to remove and exhaust manifold to get at them.

 

I have replaced the 4 on the both sides of the block and now need to get to the ones on the back of the block. It looks like the trans has got to be dropped??
It's a 2000 express 2500 5.0 liter

 

Where the heck is the profile pics I added???

 

If they are on the very rear of the engine block then yes the transmission and flex plate will have to be removed. While you are at it might want to check your rear main seal on the engine and the front seal of the transmission for leaks.