Clunks and shudders that shocks can't explain — a knock crossing driveway aprons, a cab quiver after big hits, body motion that feels a half-beat behind the frame on rough trails. Visually, look for cracked, bulging, or collapsed rubber between body and frame, or a body sitting unevenly. If your truck is old enough to vote and still on original mounts, assume they're tired.

Firmer, yes; harsh, no — the springs and shocks still do the actual ride work. What poly changes is the body-to-frame connection, so expect a more tied-together truck with somewhat more road texture and buzz reaching the cab. On a vehicle that works off-pavement or carries weight, most owners call that trade a bargain. If isolation is your top priority, stay with rubber.

Much less often than poly's reputation suggests. The squeak stories come from suspension bushings, which rotate under load; body mounts are clamped and mostly compress, so there's little of the movement that makes noise. Assemble with the supplied lubricant where the instructions call for it, torque everything properly, and a squeaky body mount is a rarity rather than an expectation.

Yes — standard practice is loosening all the mounts, then raising the body slightly one section at a time to swap each one, so the body never comes off the frame. It's methodical rather than difficult. The honest warning is rusted body bolts: on salt-belt trucks they're the entire job, and soaking them for days beforehand is the cheapest insurance available.

If the mounts are original and the truck has real miles on it, absolutely — worn mounts blur the improvements you just paid for elsewhere. Fresh dampers controlling the frame while tired rubber lets the cab wobble is buying a result and receiving half of it. The truck is already in the garage with the wrenches out; fresh mounts let the rest of the work show.