You probably don't want a soft crate for car travel. A hard sided or wire one is much safer - if you slam on the brakes, or God forbid, are hit. Measure your back area - probably a 36-inch will fit the area best and fit your dog best. He really just needs to be able to get in, turn around, and lie down. I think you can basically anchor any crate to the car, but there are probably people here with similar Jeeps who can tell you better.