A guy that I work with has a 2000 Tahoe. He had to replace the rear shocks at over $500 a piece. It has coil springs in the back. He wants to know if it is safe to tow with a heavy tongue weight, or will it cause damage to the shocks.
Is there something like an add a leaf for coils?

just put some airbags on the back if the load has too much tounge weight

i used my dads tahoe to tow my blazer a couple times. once with a load leveler connected to the trailer and once without, huge difference. without the leveler the rear tires and suspention were skwooshy:shaking:
the tranny also died shortly after, still under warrantee.
if i were him i wouldnt tow heavy loads like i did.

on that truck hes got a little more to worry about than the shocks...

make sure its properly equipped (helper bags, load distribution hitch, etc) for what hes towing...i wouldn't want to tow a lot with a tahoe personally, but it has been done.

It won't hurt your shocks... but don't go over the rating on the factory door sticker. The rear axle, suspension, tranny, frame etc are typicaly matched close to the same strength. If you beef up one thing and start towing heavier than recomended you stand a good chance in taking out the next weak link...