Hey guys have had a noise issue on my 2wd 1998 F150 that I have recently lifted. I am getting a whirr whirr sound that speeds up as I accelerate and slow as I do. Did some looking under the truck and think that my driveshaft maybe a tad too short now. Not to sound stupid but the flange that is attached to the upper Ujoint, should it be flush with the tranny or is there any shaft exposed between the end of the tranny and the flange of the Ujoint?

 

post a picture of what you're talking about

 

 

The flange on the Ujoint should it be flush against the tranny? Or is that bit of shaft hanging out normal?

 

The picture is correct. You want some space between the yoke(u-joint closest to tranny) and the tranny input. When you flex your suspension you don't the DShaft to hit the input of the tranny.....that would be bad! You're driveshaft may be unbalanced(highly unlikely) unless you look at it and can physically see a spot where maybe a weight fell off. It sounds to me like you need to get a good wheel alignment done. Maybe even a weight fell off one of your wheels.

You shouldn't need to extend your driveshaft unless you put somewhere around 8" of lift. I had to get a new driveshaft for mine. I had a similar problem where if I was going around 70-75mph on the highway and I was decending down a hill my entire truck would shake annoyingly and make that whirring sound like you're talking about.