I would say vacuum is your problem. However the cruise control thingy is under one of the battery trays.(don't remember which one. mine is electronic) Corrosion from the batteries can eat it up and cause it to fail as well. Might not be caused by vacuum but I would check there first.

Prob. drivers side tray, since thats where the throttle linkage is. I'll give it a lookaround!

ya the actuator for the cruise is under the drivers bat tray and it is vac accuated and a pita to get to and your vac pump is just in front of your power steering pump start there and follow you vac lines to try to find the leak there isnt very many so it should be fairly easy to find if a vac leak is your prob

Thanks guys! Now to become un-lazy and actually do it :lol:

if the vacuum leak is bad enough it'll cause a hissing sound too. It happened on my pickup a while back. and it controls your hvac, brakes, cruise. when i had the vacuum leak it was a pita to hit the brakes.

The brakes work great on my truck (the damn drw's are VERY catchy though..), just the hvac and cruise dont work. The hissing is VERY loud though

still sounds like a vacuum leak. kinda like your turbo is spoiled all the time?

Eh.. kinda, kinda not. It sounds like taking the brake booster line off of a gasser, how its a very distinct, LOUD blowing sound. I've heard a lot of diesels, and I wouldn't say this is a "normal" diesel noise even though it is my first cummins

gotta be a vac leak some where

intercooler may have a hole in it. i had one crack and couldnt ever find the leak until i replaced it