04 F150 SCAB - 73k - 5.4L

I "hope" its just the U-joints...and not something worse...

Noticed this 2 years ago while driving to TN. pulling a small pop-up and all loaded down. Got all the way to Pigeon Forge (900 miles), stopped, and when I accelerated I had a bad vibration / shudder. The vib would stop after about 10 mph.. It did this till we got to camp. Once I unloaded it, and even after we headed back home, didnt notice it again.

Since then we have pulled the pop-up many thousand of miles without a hickup.....until last weekend. Noticed from a stop it shudders under load till approx. 10 MPH. Any ideas?

I am suspecting U-joints because now I swear I can feel a little vibration (w/o load), and when I release the brake from stop, it feels almost like at least 3 brake calipers are slightly stuck and releasing in order (but there are not 'clunks' or anything).

 

That would be my first suspect.

 

What is the best way to check and what am I looking for?

After work I crawled under with the truck in neutral (parking break on) and cranked on the shaft, and while there was some play, I only noticed a tad on the back joint - The yoke and the shaft closed together about 1/32-1/16 after the 'natural' play in the shaft had stopped.

What exactly am I looking for?

 

I'm getting the same vibration at 10 mph too on my 06 FX4 S/Cab! I notice it on a stop and start events. I'm not hauling anything either. I hope it is something simple. Let me know if you find out the cause and i'll do the same. Al

 

Just look at the u-joint caps where the u-joint goes in. They get dried out, and you can see a gap.I had to heat the bolts up on my truck to break them loose.

 

Its your clutch packs...I'm on my 4th set

 

Try changing the transmission fluid.