if I remember correctly the center bearing is on the male spline on rear of front shaft,most are but haven't looked at mine lately

 

So, who here thinks this poorly lubricated from the factory spline has been the cause of my seat of the pants vibration for more than 100,000 miles? I've changed the U-joints twice, the center support once, both to no avail. Any and all opinions are welcomed.

 

I have a 142" wb (supercab shortbed ) with the 1 piece shaft. The quick run down was Ford installed the spring spacer blocks on the wrong sides and it made the u-joints operate at close to their maximum angle limit. Making a nasty vibration that almost felt like the freeway hop. I tow every day so no lifts for me either.

There are some guys building one piece shafts up to 65", but they are pricey and prone to vibration. 60" is the max that most shops will go.They have to be balanced perfect and they still tend to whip like a jump rope at high speeds.

The spline is the problem like you were told. They weren't lubed right from the get go and they wear excessively and do the same to the slip yoke. Mine was compounded by the fact that the incorrect factory spacer blocks made it stretch even more. There wasn't enough spline inside the slip yoke unless fully loaded. When empty there was barely enough to safely hold on. I'm surpised it never pulled out over some of the highway humps we have here in Colorado. This slop, at the right speed creates a harmonic vibration in these trucks that will drive you nuts. The key to a great shaft is all in the fabricator's hands. The less weights it takes to balance the better it will be at high speeds. Also I had mine balanced at 6000rpms in a high speed balancer as my problems were at highway speeds.

You'll be wondering why you waited for so long to do this once you feel the difference. I battled with vibrations on and off for the first three years on my truck. For the last three it's been smooth as silk. Well, as smooth as the shortest wheel base with solid axles and the heaviest leaf springs that were available from the factory can be.

You are on the right path to smooth sailing now. Make sure you let us know how everything turns out. There are a lot of Super Duty owners that just live with the vibrations. I'm glad you decided enough was enough

Austin

 

one way to check is to grab female part and push up and down to see how much play is between it and male spline
I have 125k and no viberation yet

 

I read some where that if you run empty 90% of the time you can shim the support bearing down about 3/4" to help with the alignment problem.

 

Here on FTE? If so could you please guide me in the correct direction? I will do a keyword search right now.

 

Mark, this is exactly why I suggested using an angle finder, and checking your shaft angles, and pinion angle. I would still see about getting your driveshaft balanced...

 

It's been over 30 years since I've used an angle finder on a driveline (offroad days) so what am I looking for? Same degrees each side of the center support and at the bottom of the pinion housing on the differential?

 

here is some info http://www.drivetrain.com/driveline_angle_problem.html

 

HOLY MOLY, It's fixed!! A vibration I have been putting up with for about 100k, it was primarily the male yoke at the union of the 2 drive shafts. Replaced that and balanced the drive shaft and $120.00 later it was like driving a brand new truck off of the show room floor. Thanx for all the replies. I had it done at Carolina Driveline. Had to do the R and R myself, but it was the best money I have spent on this rig in awhile.

 

glad it worked for you,I thought it was a very possible place for the problem to be

 

Reminds me, I need to replace the center support bearing. Congrats on finding the issue after putting up with it so long.

 

Glad you got it fixed - Thats a long time to have a vibration -I thought I read on here that you can install a zerk on the spline hub -But I never saw a write up on it. Also this seems like it might throw the drive out of balance, unless you put 1 one on the opposing side. Any thoughts?

 

The amount of metal removed to drill a hole to tap for the zerk fitting would be close to equaling the weight of the zerk fitting. Probaly wouldn't cause a balance problem. My .02

 

Right on! I had a feeling you'd be amazed at the difference. Now you can actually enjoy your truck instead of it wearing you out.

Austin