Got my Timbren at
www.etrailer.com for my 2004 Chevy 2500HD. The rear end road high unloaded. Had the Timbren added when the hitch was installed and we picked up the trailer at the dealer. When we hooked up the HC318RE, it was perfectly level. I understand the Timbren have "progressive" increasing support, which means it might not bottom out to the "hard" stop, leaving some cushion for a better ride. It gave my truck a nice ride. I highly recommend them.