The Stovebolt Site Forums The Shop Area General Truck Talk help - lost for what is next!

Most readers of the Forum might be familiar with the noise problem I am having from what I believe is the rear of the truck. It is not a drive line issue.

If I hit a bump or a washboard stretch of road I get a loud metallic thud. Embarrassing and scary because I have to look behind to make certain nothing has fallen off!

The best description of the noise I can give is that if you had a piece of steel plate placed across two steel beams and someone dropped a steel bar on it and it bounced, that is what you would hear. It is not always there but most of the time it is.

I have removed the tailgate, rear shocks, checked the exhaust system, removed the skirts between the bed and the running boards. I have even driven with the doors open in case it was coming from there. The spring mounts are good. I believe the shackles are good too.

I thought it might be the e-brake cross shaft as it is a bit loose in its mountings, but have wedged pieces of wood in place to tighten it up.

I noticed that a groove was worn in the e-brake shaft where the bracket from the cross member rides against it, opposite to the clevis, so have separated it and put in a piece of hard rubber to insulate it.

The bed is down tight, the boards are tight and the fender bolts are tight, none of these over tight.

The only thing I can now think is that I am missing the rubber pads from the mounting blocks. The blocks are good BTW.

I think my next step will be to raise the bed a half inch and slip in the rubber pads.
But as it is I simply do not want to drive the truck until it is fixed. I did have a 53 which did not have that sound and the only obvious difference was it had the rubber pads.

Any ideas or suggestions, as always, will be appreciated.

I'll take a guess. When I had my cab off the frame I noticed a rubber pc. that was molded on a big washer close to the master cylinder on top of the framerail. It had a trough in in that the e- brake rod rested in. If this pc. is missing on your truck maybe the rod is smacking the top of the frame?

Thanks. My e-brake shaft runs thru two brackets which are bolted to the frame - one on each side.
The linkage goes to the brakes from each side. I had a chance to grab the shaft and give it a good hit and it does move albeit a slight amount. Seems there is wear in those brackets.
I took two wood wedges and hammered them between the shaft and the cross member and made the shaft tight enough so it would not move.
But the noise is still coming thru from somewhere. I am curious about this rubber piece you mention. Exactly where is it?
After posting the above I went and removed my license plate as it was rubbing on the fender (front fender on rear) thinking maybe. but no difference.
In case anyone mentions it I also have checked out my spare tire bracket but it too is not the problem.

A trick I tell my students to use is "Take a dog for a ride". What I mean is to have someone ride in the vehicle with their head out the window just like a dog likes to ride. Make the noise happen by driving over bumps to make the sound or go around corners if that is when the noise occurs.. Do whatever it takes. The 'dogs' job is to move around and locate the noise while someone else operates the car carefully and makes it do the noise.
With your problem you could have someone ride in the bed to listen for the noise.
This technique will get you in the ballpark. It works great for noisy brakes, squeaky bushings, loose hubcaps, etc.
Rick

I don't know if this is what you have, but I had a similar noise in the '55. Drove me nuts trying to find it. After I checked the cab mounts, bed mounts, etc., I found that it was the lower seat cushion. The screws had come loose on the drivers side. Evry time i hit a bump, the seat would knock, even with my big butt in it. Might be some thing to check on yours.

Again thanks. I plan on doing the dog ride routine with a buddy in the bed. I even suggested jokingly of course, about tying him to the underside of the bed while I drive. Again, jokingly!
Not the seat assembly but good suggestion. Even with a yard of bark mulch filling the bed it still happens.
What is frustrating is that I go under and wiggle/knock/push every possible part that might move and nothing does.
How does anyone feel about the lack of mounting rubber pads? The rear bed bolts go through a steel 'block' and although they are tight do you think the fact that it is metal on metal that it could cause the noise?

My first guess is the rear axle and spring connection. But only if you have a torque tube.
Be sure you have a good and functioning rubber bushing on each side.
page 4-61 in the 48-53 service manual.
Grigg

I have a torque tube. Fill me in on the axle/spring connection please. Is this where the axle bracket (with the pivot points) joins the spring. The only rubber I know of in that area is the snubbers on the lower side of the frame rails. Tell me more please.
Incidentally for the most part the truck rides very smooth on good roads and over the occasional bumps. But when I hit that bigger hole or a washboard section of road is when it gets noisy.

Sounds like you have lost the rubber bushing, or bushings, that should isolate the pivot pin / bolt and the piece held to the springs by the u-bolts.
Check your shop manual for a picture, page 4-61.
You should be able to see if there is anything there by looking to see if the bolt is centered in the big hole, or sitting on the top edge of the hole.
Or, jack up each side by the bottom of the spring and see if the springs moves before the axle does, or at the same time.

Grigg that is one of the best tips yet, thank you. I checked page 4-61 and just crawled under the rear. I saw the mount and the rubber washers on the end seem okay - a bit dry and dirty - but not crumbling anywhere. I cannot see the rubber bushing because of its location in the bracket.
The manual suggests one method of recentering or realigning the bushing but I think I will use your idea to see if there is movement in that area. As it sits the bolt seems centered, the whole unit seems to be fine because there is dirt/dust around the unit with nothing seemingly disturbed or out of kilter.
Are these bushings available to the best of your knowledge?
Bill

should be available, but perhaps not your problem...

loose exhaust, loose tire hanger, bed wood shim fell out

Sorry Builder, none of the above. All checked. Grigg had a good point and I am still thinking that the lack of rubber pads on the bed blocks could be it. I am also looking at e-brake cross shaft.

I have a 1 ton pickup with very stiff springs. My bed is spaced from the frame by only the wooden blocks, no rubber. I have no problem with it, and don't think that is your problem either.

Sorry, I'm not talking about the e-brake cross shaft but the rod which goes from it to the end of the parking brake pedal. On mine when you follow the rod forward it goes up on top of the framerail and is resting in the rubber trough I mentioned. That rubber pc. is bolted to the top of the framerail near the master cylinder. Then it goes thru 2 holes in the front cab support and connects to the pedal clevis. I'm guessing the rod is making contact either with the top of the frame or where it goes thru the cab support. If your box mounting bolts are snug against the wood blocks the lack of rubber would only make a slight squeak at best. Good luck.

Curt B.

I will check that e-brake linkage as you suggest. However the noise is quite loud much more than a rattle. I guess it would be like rattling that e-brake cross shaft in its mounts and getting that metallic clunking noise.
Here is another thing. As the day gets warmer the sound is not as frequent. Strange!
I did try the jack under the spring pad as was suggested and raising the spring the axle came with it. Given the diameter of the rubber bushing it would take a critical eye to see any discrepancy between it and the bracket.
I did find a source for those bushings. Steele Rubber has them but you must send back the complete unit so they can do it. Price $160.00 per pair. However at this point if it would get rid of the thump it would be worth it.

drive it to Tx and I bet the noise will be gone I only know one thing that makes a thumping sound and it is not usually found in a truck

If I was chasing a rattle I could find it. But picture a piece of metal in the bed instead of wood and someone drops a piece of steel in there and it bounces a bit. That's what I am dealing with. 90% of the time it is okay but the occasional big bump or washboard road will set it off. Speed bumps don't!

olblu49, You have most likely already investigated this, but have You taken a good look at the shocks?

I have seen springs with notches worn on the bottom of each leaf, where the spring below usually ends it's travel when sliding to flex. I have seen notches that are quite severe and wonder what happens when the leafs are forced beyond this point. Do your spring leafs have these notches?

could it be a bed side or some part of the body acting like the bottom of an oil can when flexed?
You could try pushing on all the big flat parts of the body to see if it does?

In my diagnostic search I removed the shocks. There is oil canning in the bed side panel passenger side. I experimented by wedging a 2x4 against 2 pieces of plywood in the bed to hold it stiff and I still got the noise.
I am now down to the e-brake cross shaft. It is loose in the mounts and I had wedged wood between it and the cross member to keep it tight. However where the curved part goes near the cross member it is very close. Also there is a groove worn in the cross shaft where the half round crescent shaped bracket (on the cross member)is riveted.
I am now in the process of removing the e-brake cables from the cross shaft so I can rotate the shaft away from the cross member, lock it in place and test drive. The clevis pins however are rusted although they rotate okay they are frozen in place. I spent a long time cutting one off last night with a power saw and this morning I picked up a portable acetylene torch to try and free the other. I am working almost below the gas tank (in the cab) so if I don't give you an update you will know what happened!

Used the acetylene torch and got the clevis pins out, strapped the cross shaft up tight and test drove. Noise still there. One thing is interesting is that if the weather is damp or humid the noise doesn't occur as often.
My next step and i think it will also be futile is to put rubber pads on the bed mounting spots.
I have checked everything aft of the cab and am thinking maybe I should look forward and under the front end altho the sound is certainly coming from behind the cab.
Must admit that portable acetylene torch is the best!

Do you have a bumper or two, and are they and their mounting brackets tight?
Have you tried moving or pulling on every part of your truck you can get a hand on to see if it is loose.

Do you have any broken things, like a crosmember, or something missing some rivets?

Grigg. Sorry nope! I pulled the rear bumper off although it was tight. There are no missing rivets and all the bolts are tight. I have tried pulling, pushing, using a pry bar underneath and everything is snug. This is why I am so frustrated trying to find it. The only thing which is different is that there is a worn groove in the e-brake cross shaft where that crescent shaped bracket rides it. The bracket is right by the clevis for the linkage from the e-brake pedal.
At the moment there is about less than 1/8" clearance between them.
I mentioned looking at the forward part of the chassis. I know I have a slightly worn king pins and wonder if that could be making that thumping. Apart from that the front suspension is good and when I hit those bumps the steering wheel does not rip out of my hands nor does the truck jump around. But I have been told that worn king pins do not make that kind of noise.
I should also mention that there is a small crack in the top of one of those curved skirts that are bolted between the bed and the running boards. Looks like it cracked from being pushed down. I painted them recently and the crack was not there. There is ample clearance between the bed bottom and cab corner so they are not touching. But again one of the things I did during my checks was to remove the skirts to see if it made a difference. It didn't.

Worn king pins should not make any noise, and if they did they would have to be so worn that you could hardly steer it.

I guess I am fresh out of ideas now..

Seems silly but sounds like you have looked at many things. How about an incorrectly sized or improperly secured battery?

It's not exactly safe but what if you jack the rear end up so the tires are about 3 inches off the ground(make sure to set the brakes and/or put some chucks in front of it)then stay safely to the side and have a friend nudge it off the jack.With the motor off you might be able to better pinpoint the noise. :confused:

Nothing sounds silly at this point. The battery is secure as is the box. I had at one time removed the cross member behind the trans to get the trans out easier. It too is secure.
Skippy (BTW I sent you an email sometime back about Plattsburg)I don't think that would work. The noise occurs only on a hard bump and not always. For the most part the truck runs really smoothly but it is on those hard bumps that it thumps real loud.

I don't know too much about rearends but a friend of mine had a 74 int. pickup that made loud thuds here and there for about two weeks before one of the gears in the rear came apart.I called him this morning and he said his truck drove fine (with the exception of the noise)until it comepletely went.

Oh yeah,I just read you're email and sent a reply.I'm a little behind on my mail :o

Still stumped. Certainly sounds like a chassis/body problem. And it is not constant. Nice day, smooth road with some bumps and it doesn't always happen. My proving grounds are a nearby residential area with a long shallow slope road which is frequented by buses. As there is no real fast traffic and the roads get warm they get a bit bumpy from buses using their brakes to slow.

This is a long shot but check the transmission mounts and the crossmember bolts, sometimes if there lose or shot they won't rear there ugly head until you hit a severe bump. Just my 2 cents as it looks like you've used up all the options to try. good luck and keep trying.
Bob T

Appreciate all the 2 cents I can get. I have had the cross member and the trans out over the years. The noise was there way back before that. However in my recent checking I have not looked at that cross member and will right now. I will also check the battery box. The battery is tied down tight.
One thing that comes to mind happened years ago. I had taken all the bed wood out for refinishing and at the same time I did not put the 6 bed bolts back in. I drove the truck like that for a week and realized there is nothing holding the bed in place except the fenders and the running boards. I replaced the bed bolts with a piece of wood the same thickness of the boards until I could put the bed boards back in. Wonder if this thump is a result of that period of time when I drove with out the bolts in place. That is probably when I lost the rubber pads too.

Been under the truck for the last 2 hours and made a few test drives. Nothing has changed.
Found 2 loose running board bolts and 2 loose cross member bolts. Not that loose but enough that I could put a few more turns on the nuts.
Every nut/bolt/rivet has been checked under there. The only other things could be cab mounts although they are tight and the rubber is good or the missing rubber on the box/bed bolts.
May have to admit defeat and live with it, although that is not my style.

Bill,

Could there be anything laying inside one of the stakepockets?

Stuart

Do you have anything covering the beed wood? I have a steel plate in my truck that makes a good bang when I hit a big bump or small ditch. One more idea, how are the tailgate hinges? Could they have enough play to allow the tailgate to make the noise when you hit a bump?

Drew

Do you have a spare tire carrier under the truck ?
Could the springs be bad ?
Battery box ?
Overload springs rattling ?
Bumper and brackets ?
Something under the seat ?
Axel shaft end play ?
Floor pan hole missing screws ?

Taken off the following for test rides:
tailgate
shocks
bumpers
skirts between running boards/bed
overload springs were removed earlier

nothing under the seat
battery box and battery are tight
spare tire carrier is tight
bed wood is not covered but held in place with stock strips
all rivets and bolts below are tight

You can understand my frustration! Now if somebody wants to volunteer to get strapped below the truck while I drive it......! (joking of course!)

shackels and springs , wonder if a spring is cracked ?