I found the following with a Google search - I can't vouch for its accuracy, so take it with a grain of salt:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">December 4, 2007 Mike of Goshen, Kentucky writes regarding towing either 2008 GMC Yukon Denali or 2008 Cadillac Escalade four wheels down:
Thinking about a new SUV purchase. Have a 2004 Suburban now and tow it 4 wheels down with transfer case in Neutral. Can a 2008 GMC Yukon Denali OR a 2008 Cadillac Escalade be towed with all 4 wheels down (both have AWD)?
If not, what does it take to tow these 4 wheels down?
You need to use the Remco lube pump with the AWD vehicles. </div></BLOCKQUOTE>
More information on Remco's products can be found at http://www.remcotowing.com