New to the site and sorry for the long winded thread. I am a 66 year old retired heavy equipment mechanic. Over 50 years experience. I build rat rods from scratch. We race NHRA Super comp. If it is mechanical I've worked on it, fabbed it, welded it, machined it etc. I bought my 1998 Chevy Silverado 3500 crew cab long wheel base single wheel one ton brand new in late 1997 with 16 miles on it. Over 200K flawless mostly highway miles on it now. Untouched besides routine servicing 4L80e tranny and 5.7 vortec. It has a full floating 14 bolt limited slip rear with 4.10 gears. Has had many sets of front pads but only 2 sets of rear 13 inch rear shoes the newest ones about two weeks ago although the one's I took off were not worn out but had a weird wear pattern on them especially the right rear. It has the slip off drums I discovered very few of them did have. No need to pull the axles unless removing the hub for a seal or something. I pull a 28 foot race car trailer with it. Earlier this year it developed a weird really noticeable brake pulsation in the pedal that felt like out of round rotors or warped drums. It got bad enough the entire truck would shutter. The dash would be shaking, While coming to a stop you can feel it kind of slowly rocking forward and back. To narrow it down with the the with the truck rolling I used the parking brake only to stop it. The pulsation is definitely from the rear feeling like mainly the right rear. Thinking okay it's got a bad drum. I had them turned. They definitely needed to be done with 200K on them One cut .060 the other a little more. Still lots left to go. Popped on a new set of shoes from Car quest and installed the machined drums. Adjusted it up and went for a drive. The pulsation was still there exactly like it was when using the parking brake to stop. Figured the drums being that old they might have other issues so I went to Car quest and they spun em again on the lathe. They trimmed maybe .005 off the second time. Put it all back together adjusted it and drove it. Same exact pulsation in the rear. Went back and got a set of new drums that were supposed to be American made. We all know how that goes. Anyway put on the new drums adjusted it up then went for a drive. The exact same pulsation was still there when stopping with the parking brake. In the mean time I replaced the front pads and had the rotors turned just to be sure. The rotors required just a quick touch up. Maybe .010. So the issue is definitely the rears. Took the drums back to Car quest. They checked them on the lathe. They had some minor runout so they gave me my money back. I have had the truck on stands with the wheels rolling. The rims have a tiny but of side to side but it does not take much weight to balance the tires. There is no out of round movement(up or down). Pulled the wheels. Swapped the drums side to side. The pulsation still feels like it's on the right rear. Used a dial indicator to check the hub for runout. Had very little. I am in Arizona. No rust on anything. Nothing seizes or corrodes here. Cleaned the surfaces anyway. Still the same pulsation. I thought about a bad hub and/or a out of round backing plate or even a bent spindle but all three would not cause the way it feels. A bent spindle would tilt the wheel and maybe wear the tire funny but what ever direction it might possibly be bent the contact surface of the shoes should not change. The new shoes have even wear on them. I figure for the pulsation to be occurring and if it was anything but the drums I would see a noticeable up and down runout with the wheel rolling. It would basically have to wobble which is not the case. There is no play in the hub bearings. I went ahead and redid the torque procedure then back it off just to seemingly eliminate a hub or bearing issue. I won't just throw parts at it. I need to know exactly what the problem is. Everything done to this point is routine maintenance. I contacted lugnut4x4 online about a disc brake conversion they offer for the rear end in it. Ran all I've mentioned by him. He could not say if the issue would go away if I did the conversion but did not say it would not fix it. Everything logical is not fixing the pulsation issue. I have to be missing something here. I did lots of online research. I did discover some GM bulletins detailing brake issues on 1998 trucks like mine. I did not find how they remedied the problem but did find that GM discontinued the slide off drums and later in year 1998 GM went back to the drum/hub assemblies with drums that did not slide off. I read some 97 and 98 and 2000 3/4 ton's did not come with slide off drums but my one ton did. This issue is not new from the amount of online discussion that most of it point towards rotors being the problem but mine had rear drums. There are hundreds of online threads with every conceivable theory known to man. But most offer no credible rock solid diagnostics. Just some educated and mostly uneducated guesses. Some devote all efforts towards lug nut tightening and indexing wheels and drums. This all good and great for NASCAR but in my 50 plus years in the mechanical field none of it makes any real sense. In the early days impacted rotors did warp but today's factory alloy's have helped to eliminate that problem. Some even said they simply removed a tire and reinstalled it fixing the problem. That would be a definite installation problem maybe affected by rust or bent rim but my 98 truck is a definite mystery. .