Bed Shaking(Truck Bed) HaHa!!

[1949panrider]

Good Sunday Morning To All Of You Good Folk's, I am have a problem with the back part of my truck vibrating at 45 to 50 MPH. I have checked everything I can think of, D/S balanced, wheels and tire balanced twice, switch front tire to the back, I put new shocks on front and rear, all Bushings look fine. I don't know what is doing it be it has been doing it for over a year and it is no worst or better. I put the rear end up on jack stands and run it up through the 5 speed and nothing stood out. Anyone else had anything like this happen to them? Thanks

[camoit]

have you fallowed the truck while someone drives it? This way you can see what is going on by driving up next to it. You can also mount a goPro camera under neath the truck to see the drive line.

[1949panrider]

I have not thought about the camera and I will try that. Don't have anyone that I trust to drive it while I watch.

[Lem Forder]

Do you have a two piece drive shaft? If so, I would guess it's the center bearing. I had an old 2002 BMW that was perfectly fine except for one speed range right around 50 mph. Shook like hell then would smooth out again when I sped up. Replaced the center bearing and that took care of it.

[BradMph]

Maybe it's time to repave your driveway, :lmao:
Check for any kind of cupping on the tires? Are they centered on the hubs. The slightest out of center can do this. Aftermarket rims and undersized lugs can cause havoc just like this.
Wheel bearings ok? lift truck and pull and push wheel for play checking.

Camoit, wouldn't it be better if he jumped into the bed and took a ride on the bronco billy truck?

To test the driveshaft, going down hill take it out of gear and see if the truck still vibrates. This will remove driveline issues if it doesn't stop.

[1949panrider]

The truck is factory 1988 MM with factory wheels. It is a one piece drive shaft. I can look back at the left bed rail at 47 mph and watch it shake. It does not change a thing if I knock it out of gear on a down hill. Sometimes if I don't drive the truck for a few days it will shake. then sometimes it will be just so smooth at any speed. I bought these tires that are on it when I got the truck the first day so I don't know if it done the shaking with the old tires or not. I have been back to the shop I bought the tires from twice and he has checked the balance but I still think it is a tire.

[1949panrider]

I forgot to add that when I jacked the rear of the truck up and put jack stand on each side of the axle housing and run the truck up to where it should shake it did not, so that tells me it has to be the left rear tire even though it checks balance.

[BradMph]

Hmm, think it is a flat spot on the tires that is created when it sits? My MR2 will tire wottle a bit until the tires warm up and work that flat spot out from sitting. During the winter it gets worse.

I'm surprised your tire guy couldn't determine what it is. Hope he didn't put a defective tire on by mistake, but most tire places are excellent in diagnosing those issues.

[1949panrider]

BradMph, The guy that own's the tire shop is a very good friend, I have wired Hot Rods and Motorcycles for him over the last 20 Years. When I have taken the truck back to him to check the tires I am standing right beside the balance machine and I can see that the tire are not out of round or balance!!! I don't know what I am going to try to fix this, really makes no since but I know it is in the left rear even if I rotate the tires. I am missing something that is gone bad under the truck.

[camoit]

bent rim. My truck did the same thing but the tire was balanced.

[geezer101]

What about the brake drum? It might not be seated properly or out of round. Maybe take off a wheel and have a good look at it - see if there are any signs of something out of the ordinary, even remove the drum and check it over. I'm clutching at straws here...

[Lem Forder]

What about the brake drum? It might not be seated properly or out of round. Maybe take off a wheel and have a good look at it - see if there are any signs of something out of the ordinary, even remove the drum and check it over. I'm clutching at straws here...

I'm thinking the same. It seems like you've eliminated all other possibilities. Since you're sure it's coming from one side, the only other things I can think of would be a bent axle or a bad wheel bearing. But, in my experience, a bad bearing makes so much noise, you'd hear it before you feel it and I don't even want to think about what it would take to bend an axle.

[1949panrider]

I would like to thank everyone for there response, I am going to try and dig into the rear end a little deeper this weekend. I also think that I might have a bent left axle but looks like I would feel that all the time and at any speed.

[geezer101]

I would like to thank everyone for there response, I am going to try and dig into the rear end a little deeper this weekend. I also think that I might have a bent left axle but looks like I would feel that all the time and at any speed.
I would be thinking the same thing. A major component like a damaged rim or a bent axle would let you know straight up that there is something wrong. Good luck with getting it sorted, it's annoying when everything is working properly but one issue is ruining the show...

[asmyser]

i've had a bent axle once, and it shook the entire time, not just at certain speeds. However, mine was bent "alot". when I jacked mine up and spun the wheel without it being in gear you could see it being out, either way its worth a check. Another thing you could check is make sure you lugs for the bed aren't missing from under that side of the bed, at a certain speed if the nuts ar emissing the bed might rattle and vibrate so badly that it feels like what your having issues with? (big grasp)

[royster]

Maybe try mounting the spare tire and see what happens.

[pennyman1]

check the end play of the axles, especially the left rear - there could be slop that is causing the vibration at that speed.

[royster]

Here's another thing to check: make sure your leaf spring bushings are still there (!) .

[dwa]

wheel lug nuts wrong outside dia.

[Lem Forder]

Did you ever figure this out? You got me really curious.