I'm thinking of installing a Hellwig Swaybar on to the rear of my 08 2500
has anyone else done this ? will it keep the rearend stable while towing ?

 

Yes I tow a 5er and it really is much more stable in the mountains. The truck will also handle the highway loops with more stability. It is not only better handling it is much safer.

 

How well does that sway bar work if you already have air bags? I think I have seen guys on here that have both,but wouldnt the sway bar have to compress the air bag on the high side of the truck as it trys to level it?

 

I have the RoadMaster bar on my '05 and I am VERY happy with it/. IMHO it is a better anti-sway bar for late model RAM's than the Hellwig (larger diameter, better mounting location, better shape)... although the Helwig offers better ground-clearance.