Clunking noise

[Rbc123]

Hi never had to ask a question on this site, most of questions were already answered. Can't find information about this problem.

Working on 78 fj40 all OG. 85000 miles. Deep clunking sound from under driver and passenger feet. Going over bumps and potholes. Sounds just like the exhaust hitting the frame, but that's not it exhaust is solid.

What's been done so far, new motor mounts and transmission mounts, new shocks, all new spring bushing all around. Universals all solid. Bin under there with a pry bar at a loss. One other thing, when your at a stop and kill the engine you can hear a quick and soft clunk clunk sound. Other then that runs strong tracks straight no pulling and stops straight.

Any other ideas?

Thanks Roger

 

[charliemeyer007]

Did this just start doing this? What tires/rims are you running? How much room is there between the bump stop and the frame. How big of pot holes/bumps and at what speed are you hitting them.

So have you checked all the bolts/nuts under there to make sure things are tight?. A friend bought a used truck, the tranny/transfer fell out months later because the guy that did the clutch didn't tighten the bolts.

 

[Sky King]

Worn, sloppy slip joint on the drive shaft?

 

[70 FJ40]

Say you put on new shocks. Check those again. They may seam tight but give them another look and make sure.

 

[Rbc123]

Did this just start doing this? What tires/rims are you running? How much room is there between the bump stop and the frame. How big of pot holes/bumps and at what speed are you hitting them.

So have you checked all the bolts/nuts under there to make sure things are tight?. A friend bought a used truck, the tranny/transfer fell out months later because the guy that did the clutch didn't tighten the bolts.

Yes just started oem rims tires 30x9.50 r15s I think enough room small potholes and small bumps all speeds, spent some time under there looking and feeling.

 

[Rbc123]

Worn, sloppy slip joint on the drive shaft?

That's tight

 

[Rbc123]

Say you put on new shocks. Check those again. They may seam tight but give them another look and make sure.

Probably put about 50 miles since installed and did recheck.

 

[77mustard40]

Make sure your axle u-bolts are tight at each spring perch, I had on work loose and was able to feel it through the floorboard.

 

[John Smith]

Does this truck have drive flanges or manually locking hubs on the front axle? Have you verified both drive shafts are in phase as far as ujoints, and that the joints are not worn out? What you are describing sounds like a worn out ujoint to me.

 

[charliemeyer007]

Put it up on jack stands and then check all the suspension parts.

 

[roadstr6]

Check your hood hinges. The sound of the hood bumping around on worn out hinges transmits through the cowl and resonates into the floorboard area. Mine did it mostly when hitting bumps and potholes. Normal flat roads were quiet. Cheap fix: Cut two sections of 5/8 heater hose and lay up in the cowl under the hood hinges and see if the clunking persists. Better fix: Replace hood hinges or get the nice new stainless pins from @SMG .

 

[Rbc123]

Make sure your axle u-bolts are tight at each spring perch, I had on work loose and was able to feel it through the floorboard.

Make sure your axle u-bolts are tight at each spring perch, I had on work loose and was able to feel it through the floorboard.

All tight no shiny rub marks.

 

[Rbc123]

Put it up on jack stands and then check all the suspension parts.

That is my next step, when I have a few hours.

 

[Rbc123]

Check your hood hinges. The sound of the hood bumping around on worn out hinges transmits through the cowl and resonates into the floorboard area. Mine did it mostly when hitting bumps and potholes. Normal flat roads were quiet. Cheap fix: Cut two sections of 5/8 heater hose and lay up in the cowl under the hood hinges and see if the clunking persists. Better fix: Replace hood hinges or get the nice new stainless pins from @SMG .

I will take take a closer look, but I believe they are both tight.

 

[Rbc123]

Does this truck have drive flanges or manually locking hubs on the front axle? Have you verified both drive shafts are in phase as far as ujoints, and that the joints are not worn out? What you are describing sounds like a worn out ujoint to me.

Manual locking hubs universals feel tight with pry bar driveshaft has no play you can't get them to clunk getting on and off the clutch. Two people bouncing on the bumper can't duplicate the noise????

 

[roadstr6]

I will take take a closer look, but I believe they are both tight.

I thought mine were too, and I never in a million years would have thought that the hood would have made such a solid sounding clunk. I thought it would be a tinny, rattly sound, but it wasn't. It sounded like someone smacking the floorboard with a rubber mallet.

 

[Rbc123]

I thought mine were too, and I never in a million years would have thought that the hood would have made such a solid sounding clunk. I thought it would be a tinny, rattly sound, but it wasn't. It sounded like someone smacking the floorboard with a rubber mallet.

That would be an easy fix. Could you also feel it?

 

[roadstr6]

That would be an easy fix. Could you also feel it?

Yessir. I sure could. Hopefully that's your problem. It would be nice if it was.

 

[RevISK]

I also have a clunk I assumed was suspension and/or drivetrain related.

I like the hood one better, I’ll take it.

 

[45Dougal]

Body mount bolts all present and correct?

My battery box had a stress fracture that allowed it to swing about a bit - could be another possible I guess.