I have a 99 150 extended cab....It is lowered with a 2/4 drop. It has the auto trans...here is my concern....first of all my truck was properly lowered, even had the rear end shimed for drive line angle...I have a constant vibration while between 55 to 65 mph...before or after that its gone.....if you are firm on the gas you cant notice it while your driving through that spped range. But if your graqdually accelerating or holding a steady speed while in that range you can feel it. Some times its not hardly noticble. Any way I had the truck inspected and no one seems to know what is causing this. They say the u joints are good and the slip yoke doenst indiacte it is worn. The rear end seems to be fine....I think it a u joint but the shop says no.....any Ideas? And no the driveline is not bent. This just started about three months ago and does not get worse. Let me know so I can point out suggs to the shop. Thanks!

 

Two things come to mind for me.
Sometime an out of balance tire will vibrate at certain speeds and not at others.
Also, I had a simular problem with mine. It would vibrate at highway speeds like the tires were out of balance. It was the rear u-joint. It was sticking a little and you could see the indentations in the race after it was changed.
Hope you figure it out.

 

Thanks for the info....already ruled out tires. they r new. This only happens while on the throttle once you let off the gas its gone.

 

Was the driveshaft removed and put on a balancing machine? Was the extension housing bushing checked? Were the yellow marks on the driveshaft lined up with the yellow lines on the companion flange?

 

drive line has never been removed, the truck has been lowered for 18 months....no problems unitl a few months ago.....I had the tail shaft looked at and both shops do not see anything abnormal. One shop said, drive it till it breaks.....easy for them to say...I think it is a u joint but the shops diagree because there is no obvious signs.

thanks for the reply!

 

If the driveshaft hasn't been removed, they can't check the surface where the extension housing bushing rubs with the slip yoke. You can shake the hell out of U-joints and see the excess play in about 10 seconds. If they haven't checked the runout on the driveshaft while it spins, they don't know squat. This "visual" inspection that you received sounds like nothing more than a starting point IMHO.

 

Ok, there is some play in the area of the slip yoke. However both shops said its normal. I verified the play on another like truck. The shop said if your bushing was so worn that it makes a vibration that I should have a leak as well. Now remember this is two different shops saying exacly the same thing. They dont think it is in the rear end or tranny but in order to elininate sources they wanted to replace the slip yoke....at a cost of 240 and start there, i think this could get pretty expensive. Im lost that they cant find what the problem is.

 

It takes about 5 minutes to take off the 4)12mm/12pt bolts to remove the driveshaft. Only at this point can you see the "surface" on the yoke where the bushing rides. If they both look fine, and your fingernail runs smooth across it, then you don't need it. Next, make sure the "yellow" paint on the rear of the driveshaft matches up with the yellow paint on the companion flange (common mistake if ever removed). Beyond that, take the driveshaft to a reputable shop that specializes in driveshafts and have it checked/balanced. They will spin it and check balance and runout. This is the normal course of action for a proper evaluation. TSB #01-9-3 also applies to certain F-150s with similar problems.

 

The full TSB, max mitchell referenced is here: https://www.f150online.com/forums/sh...hlight=housing

I checked mine a few weeks ago and there is a lot of play in the output shaft. I haven't heard anyone say definitively that this is a problem but I have to imagine that if the driveshaft is out of balance the least little bit, there will be a vibration.

Probably good to have it checked for proper balance.

My truck vibrates at the same speed and I'm about ready to rip the extention housing out of there!!! I am so upset about the design issues with my truck that if I lived next to the dip$**** engineer who developed it, he'd be on a first name basis with his proctologist for all the parts I've replaced.

This is what happens to the extention housing when things really get out of hand: Compliments of, Deacon. https://www.f150online.com/forums/at...&postid=474709