I just got my 1948 F-4 a month ago and since I've had it it has made a noise like there is a troll underneath banging on the frame or something. The noise starts occurring when I get up to 10mph, and keeps steadily increasing with speed. I timed it as best as i could and it bangs every 1-1.5 seconds at 30mph which a fairly slow occurring noise. when i jacked the rear up and rotated the wheel it sounded like the noise came from the rear U-joint. I can still drive it around too. I am terrible at diagnosing things but most of all i hope its not the rear axle.

 

you might have bad u joints or bent drive shaft, check the joints by trying to move the shaft up and down at u joints if there is any play the joints are bad , hope this helps.ASH

 

The exhaust pipe is not hitting somewhere is it?

More than likely just a bad U-joint though. Not hard to replace at all.

 

Sounds like maybe U joints. There should be a zerk fitting for lubrication on the U joint. Try squirting some grease in there and see if the reduces the thump noise. Raise the rear wheels, with the truck in the air, start it up, run it and have someone listen where the noise might be coming from or possibly see something moving up and down more than it should . I'd check the gear oil in the rear end also. If its low or no oil, they'll let you know too. If it's a stick shift, check the oil in the tranny.

 

I'm with Brian on this one. I bet there is a piece of metal hitting the frame. Seems to me that a U joint would make a thump faster than 1 sec @ 30mph, but ya never know.

 

Im looking forward to checking some of those things mentioned tomorrow. If I find out I'll let you know who wins. I really hope its u-joints. If its a bent drive shaft what is the procedure there. Would I be able to replace it with the one I just took off my 81 F-150 that would be handy.

 

Man, sure sounds like a troll, to me!!! Just leave a big mug of warm beer, by the truck, and if it's gone in the morning, you KNOW it's a troll! They are hard to catch, but if you do, they have a big pot of gold, th....uh....nevermind, that's leprechauns!!

My guess would be u-joints also, but that long between noises, doesn't quite seem right...just about everything at 30 mph would be turning faster than that. Is it 100% constant? I mean, EVERY 1 1/2 second, or maybe 2 or 3 times, than a longer pause, then again? That would strike me as metal to metal bumping. Anything else that is 100% consistent, I would think would be rotating faster than that, so the time between noises would be much shorter.

Yeah, let us know...

R

 

Yea its constant doesn't miss a beat, that's kind of how I ruled out a troll he would have to get tired sooner or later.

 

On a larger truck like that, first check the rear wheels to see if they are tight and make sure you don't have one cracked, as they will make such a noise. With the noise occurring at that speed, I would think something rotating at road speed, wheels, tooth chipped on the ring gear in the rear-end, or could be a s simple as a flat spot on a tire and a bad shock bushing. Good luck and let us know the outcome.

 

Look for anything loose or hanging down under the truck near the driveshaft area...could be something is being "kicked" up and into the frame by the shaft as it turns....at 10mph it has enough rotation to hit the frame and at 30mph it's pretty steady and quicker of a "kick". Loose under bed tire carries, tailgate chains , etc... I would thing u-joints, ring gears (rotational things would be a quicker noise.
Ed

 

Hey Bryanswens

I had a 1954 Military Studebaker 6X6 I hauled scrape in, went camping in and drove to the beach. The beach part was cool cause my friends and I would set our lawn chairs in the bed and roll the canvas top up and enjoy the shade… as well as the view.

The truck had a noise similar to what you are describing and it turned out to be one of the rims on one of the back axles was out of round and would cause the truck to hop ever so slightly. When the harmonics were right at about 30 MPH it would make the muffler clunk on the frame member above it at about 2 to 3 second intervals. When on jack stands the noise was gone and it drove me bonkers for about 6 months until I had all new rubber installed and the bad rim was found when they were trying to balance it.

Just a thought… Big rims turn slow

Later

_____________________
My Grandpa told me once that you have to learn by the mistakes of others because you will NOT live long enough to make them all yourself.

 

Well after I got off work I checked the U-joinst and the Drive shaft. The U-joint seemed to have a little play in it so I removed it and began to replace it with the new but realized I had bought the wrong one. Does anyone know where to get a rear U-joint for a 1948 F-4 dually it has three u-joints. Also upon further inspection the part that goes into the Diff seems a bit of wiggle to it. It doesn't move in and out but, Up Down Left Right. (See Illustration)



Could this be a outer pinion bearing that is causing all this noise, also when engine braking the gears do make a meshing sound like they are coming together harder than normal but when i press the gas it goes back to the banging noise.

 

You might try a place called Joblotauto Inc. in New York. He tends to have bigger truck parts probably U-joints and other parts you might need.

 

it looks like the pinion seal is laeking,it is possible you have a bad pinion bearing which can cause knocking noise.

 

I have thought of using it for camping and such but I dont think i could get the wife to go along with it.