Thumping noise from the back

2000 AC V8, 133k miles

New shocks, new rear brake shoes, lubricated drive shaft, changed rear diff fluids.

In the last few rides, I've been hearing a noise from the back. I only hear it from 5-15 mph, if I drive faster than that, no noise. The noise itself sounds like something is loose and is rattling in a plastic box, like a thump I hear only when going slow and I seem to be able to make it sound if I swerve left and right.

I considered rear hubs, so I lifted the truck, and I can't feel any movement in the wheels.

I went under the back, and tried jiggling the shocks, driveshaft, suspension pieces, spare tire - nothing jumped out at me as an obvious issue.

It is driving me crazy - is there a known issue that would cause a noise in the back I might be overlooking? Can it still be the hubs if there is no play to the wheels when lifted, and no leaks on the hub?

Thanks!

 

Could you have someone walk beside it while you drive forward and try to identify the source? Or maybe ride in the bed? Wish I was more help.

 

I tried riding in the bed while my wife drove, and I could hear stuff somewhere below me but couldn't identify where it came from.

Then, I had her turn the wheel hard left and go forward, then back just a few feet, and I could hear a noise, but again, couldn't identify it.

It is driving me insane.

 

Giggity

 

maybe a missing bushing in the new shocks? Broken Leaf spring?

 

I feel your pain. Identifying mystery noises is torture. Are you positive it's coming from the rear of the vehicle?

 

Might have to try this. If Keanu Reeves can do it at 60mph, I'm sure you can do it at 15.

 

And while he's doing that, I'll be making thumping sounds with Sandra in the back of the truck

 

I’m pretty confident that shocks have everything - they’ve been on the car for a few months and this just started.

Broken leaf sounds like it could be a culprit, I haven’t checked for that. Heaviest load it gets are my three dogs but you never know, so I’ll check on that, thanks!

 

Well, it sounds like it but I am not 100% positive. I have been thinking about lifting the front to check the suspension and hubs to see if the noise is something manifesting itself in the back.

 

I’ve been thinking about removing the bed and riding on the chassis to see if I can identify it. It’s really stressing me.

 

Still have OEM Springs? If so, your silencer pads might be either missing or worn out and crooked. They are the little thin washer plastic pieces that go between the spring leafs.

My truck was making a ‘clunk, clunk’ noise at low speed turns doing 90° turns up into driveways or shopping mall apron inclines. It was the ‘silencer pads’. The noise became more pronounced after new shocks.

I jacked up each side and wedged some plastic shims between the leafs and cured it. Used Fuze caulk to hold the shims in.

 

Very interesting thought. I have one, that’s sounds like it might work if the mic can pick up this sound over the road noise.

 

This sounds like the most promising thing yet! Are these shims something that goes at the front and he back of the leafs? Any chance for a photo of what you’re talking about?

I have to say - you are like a 1st Gen savant. Thank you !!

 

I’ll post some pics of the shims tomorrow. Readily available from big box plastic/composite shims. Cut the tips off and use them at each over lap of leaf on both front and back. Squeeze some Fuze on one side only and wedge in so the other side ‘slides’ over the moving leaf (as the silencer pads are designed).

Jack up the rear so the axle hangs and wedge (carefully) a flat bar into the side of the leaf to pry it open enough to slide the wedge in. Do not force the flat bar action or you will break the leaf. Just enough to wedge about a 1” long piece of shim.

 

I just played with some laminate floor shims. There really wasn’t any room at the ends where the existing washers are, but I didn’t jack the truck. But the sound might be like metal on metal rubbing which could be the springs. Frustrating.

 

Anything that allows the springs to slide will work. Trick is Fuze’ing it to stay on the one leaf while letting the other leaf slip on the slippery opposite side.

Otherwise, it new springs time because the removal and re-install of the old springs with new silencers isn’t worth it. Better off just getting an entire new system $$$. Did I mention I hate doing suspension work?

 

If I knew this was the issue I wouldn’t care - it’s not the noise that is driving me insane, it’s not knowing if this is a sound of something large and bad to come.

 

Good news is its something you did to make it this way, and by default something you can correct. Just reverse your steps and figure it out.

The shim thing worked in my case. The new shocks magnified the prior clunk clunk on 90° turns. My OEM springs keepers were splayed from years of tow/haul/play. The silencers were pushed out and or missing.

Hard to say exactly whats up in your case without being there. Keep us posted.

 

Noise just started, weeks or months after my last job on the truck (rear shocks). So, I am not 100% sure it was caused by my work.

I found a place that does Pre purchase inspections and also can do diagnosis for certain issues. I might have to have them look for it and then I can fix it.

 

I hate to ask this, but do you have your trailer hitch in the receiver?? My sister thought her Jeep was falling apart from the rear end, it was only the trailer hitch rattling in the receiver.

 

I had something like this in a subaru once. Turned out the jack was rattling in its cubby. Worth checking out at least.

 

I have used a go pro under my truck to spot noise sources before. It can be difficult still but if you watch what is moving when the sound happens it is helpful. Is your spare tire secure under the bed?

Sounds like lateral load is causing the symptom. Does it happen on smooth roads or just when you hit bumps or turn? Lateral action has me thinking maybe a bearing.

Thumping has me hoping it isn't your diff. My diff thumped at low speeds and at higher speeds, especially when I let off throttle, sounded like some beer cans were bouncing in my bed. I put the rear axle on jack stands, blocked the front wheels and put my truck in drive. Then I crawled under to listen, I could hear the clear thumping sounds from my diff. A c-clip broke and a pin was sliding out of position and bouncing off my ring gear. Hope you don't have that problem.

 

Thread revival but are we talking about these?

https://www.homedepot.com/p/8-in-Composite-Shim-12-Bundle-10011700/301757699

Cut into 1" pieces and caulk?

Back of the truck starting to sound like a rubber ducky after latest muddy/dusty adventure and I think it is the leaf springs so may have to do this.

 

Check your body mounts. The early sign of mine being faulty was turning left or right and hearing something metal shift in place.

Since my bad body mount was on the back left, I thought it was the stock jack shifting in place under the rear seat.

Once the mount completely collapsed, I realized it wasn’t especially when one side of the cab sank lower than the other. I did think it was a leaf spring bushing originally, but inspection of the mount proved otherwise.

 

Dammit! I didn’t even realize this was an old thread.

 

I just bought these leaf shims to hopefully cure a similar noise

 

I used the same shims; bought them off Amazon. It's a cheap, easy and very effective fix for problems like this. I added grease to mine, explained in this thread:

https://www.tundras.com/threads/popping-noise-when-turning-fixed.107586/