I have a 07 fx2 f150 with 70,000 mi . in the last 10000 mi ive picked up a vibration that seems to be coming from the left rear end. Ive changed the tires , swapped tires from front to rear, replaced the left rear rotor thinking it may be warped. the shaking can be felt all the way through the truck but i can watch the back left side of the bed shake at around 49 to 55 mph. I also have a clunk in the rear end when starting out but i've read that i can grease the slip yoke to cure that( will do this week). I don't hear any roaring from a bearing or anything. this is driving me crazy. Does anyone have any ideas or had a similar problem. thanks for any info. ps, i've also put the rear on jack stands with no tires and had the same vibration at 50 mph.

 

when mine did this, it was the rear universals. i figured it out when i dropped the driveshaft on the road pulling off from a stop sign. that was an expensive lesson. universals are WAY cheaper than a driveshaft...

 

I'll check over that again and report back. thanks

 

yea give them a good look. my truck was doing exactly what you described. i even lost the "thunk" when putting the trans in gear. like you, i thought i had a tire going bad... until i had to run back and pick my driveshaft up off the road... if these driveshafts drop like that, they have to be replaced.

 

What is the best way to check the u joints? I am having the same issue. New tires, rotated and balanced numerous times, new RP rear end oil, no improvement.

 

if it were me looking, i'd put it on the rack and see if there is any play in the universal. torsional and side to side. i'd also take a good look at them to see how they look. universal bearing caps are cheap and pretty simple to do if you just want to knock it off the list to be safe.

 

I was told you can't replace my u joints on my 05 I need a new axle they said numerous shops.

 

You don't need a new axle, you need a new driveshaft - unless you buy a kit specifically made to replace the staked u-joints.

http://www.drivetrainamerica.com/p-6...up-staked.aspx

 

That's what I ment to say sorry about that. I would just buy those? How many would I need and how hard is it to do? Can you do it at home?

 

Not only these suggestions, but check your ebrake... I've had it happen way too many times and the entire truck shakes violently.

 

Well, i spent half the day saturday to change all three u-joints on the drive shaft. I also greased the front and center splins good. The center bearing felt smooth when i turned it, so i did'nt replace it. The vibration is still about the same. I don't have the thump anymore when i leave the stop light, but i think the greased splins took care of that. One thing i discovered is the output shaft coming out of the rear of the transmission has about 6 mm of play from center point in any direction. Even after installing the drive shaft it still has some movement . Does the trans shaft supposed to be tight or is some free play normal? I also made sure the e-brake wasn't stuck on both wheels. Anymore ideas?