I'm new here and not real savvy with where to post this. I have a 2007 F150 Supercrew XLT 2wd 5.4L that has a mean shake in the bed at 57-60 mph. The best way to describe it is the bed looks like it's twerking literally! Tried different wheels and tires No fix, new tires no fix, new drive shaft, knuckle, slip yoke and U joints and no fix. New shocks nothing! I have done the spark plugs and coils. My truck has 93,xxx miles with a leveling kit and 276/65r18 and a Magnaflow 3" single in-single out. Only thing I haven't done was rear brakes but there not hanging up and I noticed there is some play in three of the rubber isolators for the exhaust hangers. Any help would be much appreciated!!

 

Possibly motor mounts or hardware securing the bed?

 

A motor mount for bed shake? Bed bolts are all tight I was wondering if it could be the clutch plates in the differential? It's a 3:55 limited slip and I just serviced it and put friction modifier and didn't notice and large flakes of metal when drained.

 

Every time I had the bed bounce, it turned out to be tires out of balance.

 

Bluejay- I have thought that but after several road force balancing,different wheels and tires and now new tires I've ruled that out but I wish it would have been that though

 

I had this same problem. 2008 F150 with 29,000 miles on it. Put new tires on, 1 set Hankook, 1 set Michelins, all at Ford dealer. Finally took it back again (had been in many times). They rechecked the Michelins again and all 4 were out of round. Put another set on and no more shake. They had checked u-joints, pinion angle, on and on.
Jack

 

I've taken notice since reading a thread here a few years ago, seen quite a few with bed shake at 55-60 mph range. Mine does NOT do it but mine also has a chunk of cast iron above the left side rear frame rail secured with two bolts through rubber bushed mounts. There were some threads here about these weights, believe it was decided they were to counter or dampen of kill bed shakes.

Here's one thread ..... https://www.f150online.com/forums/20...-solution.html

 

I will say that this shake started around the same time I removed my stock muffler and went to Magnaflow. I don't know if the weight of the stock muffler was also used as a counter weight. I know the stock muffler was three times the weight of my Magnaflow and I have realized the lower my fuel tank is the shake becomes dangerous. This shake has been a pain for 1-1/2 years now and has cost me a lot in tires!

 

Maybe do an experiment with weight in the bed at varying amounts (sand or gravel bags) at different areas of the bed. Doesn't seem something like the weight of the stock exhaust would make a noticeable change but who knows.
It'd be a cheap way to rule it out.

 

I've got one bad tire that is separated and won't balance correctly that causes this. New tires can come off the shelf separated. Did they put a lot of wheel weights on your tires to balance them? Do they have a road force balancer? Does it change if you put more air pressure in the tire?

 

Ok, so last night I pulled the rear brakes off to discover that my parking brake was set wrong. The parking brake shoes are shot because they had been dragging more than they should have been which caused the rotors to warp and one of the shoes to crack. I removed the parking brake assembly and put new rotors and pads and the shake is not anyway near as dangerous anymore but I do believe my transmission mount is separated at the rubber so that'll be next

 

Yes, old motor and tranny mounts can allow a harmonic to setup and cause a shake. Urethane mounts will eliminate if an issue, but will result in you feeling more motor vibration.

 

Well after the brakes I thought the shake was gone but it wasn't. But on a good note I have isolated it and it was my exhaust. The sock hanger isolators were much bigger than the rods welded to the exhaust pipe so the tail end of the exhaust was what caused the real bad shake due to the excessive amount of movement in the exhaust isolators. Put a new isolators/hanger on the furthest end(tail) and its smooth sailing. It's crazy how light these beds are on the Supercrews!! The smallest thing makes them go haywire. So all you guys that have after market exhaust and have the violent shake-check those hangers. Mine is just a 3inch Magnaflow single in single out with a 4inch by 12 inch stainless tip.

 

This should help, my next project!