Thumping noise under floor board

stang1986gt · Post by **stang1986gt** » Mon Sep 18, 2006 10:12 am

I tried to post this in the suspension section, but I keep getting an error that access is denied on this server:

I keep hearing a thumping noise under my drivers floor board when I hit bumps. Bushings look ok, it's not the tranny mount or the u-joints, nor is it the exhaust (as far as I can see). Any ideas?

The truck also dives to the right a little when I hit the brakes. This may be unrelated and just need to be adjusted or need new shoes, but it's worth mentioning.

67highboy · Post by **67highboy** » Mon Sep 18, 2006 11:00 am

67highboy · Post by **67highboy** » Mon Sep 18, 2006 11:02 am

It wouldnt let me post dang-it.
r a d i u s a r m b u s h i n g s is what I would check out first

67highboy · Post by **67highboy** » Mon Sep 18, 2006 11:03 am

This site doesent like to talk about those bushings I guess cause it wouldnt let me post those words together

stang1986gt · Post by **stang1986gt** » Mon Sep 18, 2006 11:31 am

I know this is a stupid question, but those are the big bushings that are mounted to the large arms running up to the front suspension, correct? They "look" ok, but how do I tell if that's the problem? Just jack up the truck and see if there's any movement up and down?

67heavystepside · Post by **67heavystepside** » Mon Sep 18, 2006 11:51 am

believe it or not , check your cab mounts. make sure there not loose , broken, or rotted out. my 67 did the same thing, my front passanger side mount was broken, allowing the mount to bang on bumps, replaced both mounts and bam! it was fixed. i spent about a mounth and $400 dollars on king pins, coil springs , tie rods , and many more bushings.

stang1986gt · Post by **stang1986gt** » Mon Sep 18, 2006 12:00 pm

Good point. I don't believe they are rotted out, but I'll check to make sure they aren't broken or something. Thanks for the tip.

67highboy · Post by **67highboy** » Mon Sep 18, 2006 12:04 pm

yea. good idea.
I never thought of that one

But yes those are the R.A. bushings.
Take a big pry bar and pry the whole I beam forward and back. with the truck suspended by the frame on jackstands so your suspension is in the relaxed state.
if they are bad you will see alot of movement back where they attatch to the frame.

stang1986gt · Post by **stang1986gt** » Mon Sep 18, 2006 12:14 pm

Ok, thanks!

67heavystepside · Post by **67heavystepside** » Mon Sep 18, 2006 2:20 pm

67highboy wrote:yea. good idea.
I never thought of that one

But yes those are the R.A. bushings.
Take a big pry bar and pry the whole I beam forward and back. with the truck suspended by the frame on jackstands so your suspension is in the relaxed state.
if they are bad you will see alot of movement back where they attatch to the frame.

i wasn't talking about the ra bushings , i was talking about the front cab mounts,you know- where the cab mount to the frame.

stang1986gt · Post by **stang1986gt** » Mon Sep 18, 2006 2:21 pm

I think he was answering my earlier inquiry as to where the RA bushings were. I knew, but I just needed confirmation. haha

67heavystepside · Post by **67heavystepside** » Mon Sep 18, 2006 2:23 pm

whoops

Clarko · Post by **Clarko** » Mon Sep 18, 2006 4:46 pm

We can't talk about RA bushings?

radius arm

I tried several different things and it doesn't like R.M B without the period between the R and the M

mcarlson11 · Post by **mcarlson11** » Mon Sep 18, 2006 4:56 pm

also, check your center carrier bearing on the driveshaft, this goes bad and allows the driveshaft to move up and down when bumps are hit, causing thud noises.

SmokeyBear · Post by **SmokeyBear** » Mon Sep 18, 2006 7:05 pm

You've inadverdantly ran over a crazed rabid midget. Take a long stick with and tape a hersheys chocolate bar to it to lure him out.

I'm sorry, I'm just in a goofy mood today.

Check your I-beam bushings, the ones that are connected to the points under the engine cradle. Those will cause both the symptoms you are describing.