Have towed for years with various vehicles. And have always followed the general rule of levelling the tow vehicle front, back to pre-tow hookup. In fact, I just read through most of the Sticky at the top of this sub-forum, where it states "GMC specifies that 100% of the rise should be eliminated". Keep in mind that this sticky is quite old (although some new to towing may still refer to it).
Have been reading through the manual for a new Sierra 2500/3500, and in the towing section it describes measuring the pre hookup front height (H1), then the post hookup height (H2). Then set the WDH so the new height is 1/4 of the difference between H1 and H2, below H2. So if H1 is 30 and H2 is 32, then 32-30 =2 and 1/4 of 2 is .5, which is subtracted from H2, so front height while towing and with WDH would be 31.5.
I have never owned a 2500, so wonder if this is HD specific or if this is now the recommended method for towing with all GMC trucks (don't know about the other makes)?
Marv
