help trace a rattle and thunk that has me stumped

[K30Blazer]

I know this is a long shot as the truck is pretty far from stock now, but I have two rattles that are driving me crazy. One is a high frequency that comes from lower speeds and bumps and one is a heavier clunk that takes larger hits to happen. Both are absent when on the freeway. Both coming from passenger side, one feels as if it is hitting the firewall but can't find anything.

Myself and three friends have spent countless hours trying to find the source and can't come up with anything. Everything is tight, no witness marks that we can see and everything that could move (harness, trans lines etc) has been zip tied down.

So far I have checked:

bearings, all steering and joints, body mounts, radiator, battery, shift linkages, headers and exhaust, spring hangars, fuel and trans lines, ac lines, crossmember, motor mounts.

I am out of ideas.

 

[diesel4me]

I don't see shock absorbers on the list--maybe one has a dented cylinder and the piston in it gets "stuck" in one spot,then breaks free,or the piston rod is bent..bad shock bushings too maybe ?..

 

[Blue85]

Is the glove box latching tight? Is the door rattling on the striker bolt? Anything loose inside the door? A loose front driveshaft slip joint can make a good clunk, but generally much quieter in 2WD than 4WD. Check the shock bolts to make sure they're tight. Look for missing rubber bumpers on the hood and doors.

 

[K30Blazer]

Is the glove box latching tight? Is the door rattling on the striker bolt? Anything loose inside the door? A loose front driveshaft slip joint can make a good clunk, but generally much quieter in 2WD than 4WD. Check the shock bolts to make sure they're tight. Look for missing rubber bumpers on the hood and doors.

It is definitely outside the interior and decently heavy. The shocks are good, the noise has some repetition to it as though it is something heavy rattling against something else. Not hollow either. Kinda sounds like a loose battery might sound

 

[jeff in co]

Leaf spring center pins or U-bolts?? Spring pack moving or any leafs moving?

 

[Kain]

i chased a rattle for a few days turns out one of the baffles inside my muffler let go and rattles. going to replace it in oct.
would do it sooner but to many doctor bills from feb.

 

[diesel4me]

Passenger side huh..firewall area..hmm..heater blower motor and the heater core or box might be doing it..maybe some mice are living in there too....
Perhaps someone dropped a tool down inside the cowl where the wiper linkages are..I found a rusty 3/8" ratchet in there on one of my trucks,it slid down into the kick panel area where the floor vent is--took the kick panel off when I was thinking about putting speakers in them..(and decided not too-)...

 

[blazinzuk]

One thing I have learned chasing rattles.

Until you have actually eliminated it, never rule anything out.

Sounds transmit. They change.

Only rule something out after you have verified it's not the culprit

 

[K30Blazer]

ha, not a bad idea about the wrench. Would be a large one though. I have vintage air, so not the condenser etc. I will keep searching and post up when I find it. Driving me crazy. I know truck is solid, just feels like it is gonna fall apart when I hit a pothole. lol

 

[blazinzuk]

So my suggestion is wait till dark and go over all your suspension and steering and body mounts and your entire frame.

This usually requires friends to bounce the truck as needed. Beer helps in this endeavor.

The flashlight helps because you concentrate on that single point of light with no other distractions