Searched around but couldn't find anything conclusive, found a thread on a similar problem on Pirate but it wound up being a U joint problem, which I'm fairly certain it is not. Installed my new Tom Woods rear driveshaft (XC long life splines, 1310 u joints), installed a new rear yoke on my Dana 18 (non-parking brake type), new fluid for Dana 18 and flushed my transmission (SM420). Put like a whole tube of grease into the new driveshaft, tapped with a hammer to seat the U joints outward. New u bolts. First drive got some driveshaft noise when I'd let off the throttle in gear, more grease fixed it. Now my Jeep's started to make a new noise, sort of like a clanking sound. At first I thought it was my exhaust hitting something but ruled that out. The most peculiar part is that it only makes the noise when I'm going around 30 or more miles an hour and giving slight throttle. If I'm fully off the throttle or on it more than 5% (measured by the TPS on my Holley Sniper EFI) the noise disappears. Only if I'm under some load but low load. The noise is constant, I swear it sounds like something is flopping around down there banging into the frame or something. The noise doesn't change with engine speed (RPM). Tomorrow my plans are to check for anything loose hitting the valve covers or something under the hood, regrease the rear driveshaft (gotta do the front anyway) and if I can't figure it out from that I'll chock the front wheels, put the rear axle up on jackstands and have my wife work the throttle for me while I listen. I'll be careful, I promise! Nothing is low on fluid, I have Warn lockouts on my Waggy front Dana 44 so it's not the shafts up front. Any ideas?