slip yoke needed to be grease...I dont trust ford so i did it myself since i m very good with hands since i built my jeep into rockcrawling..soo..here what I did and reasearch..

so far what I have done..

I tried Ford Telfon grease as per TSB..only last 2 weeks!!

Regular Mobil one grease.. last about 34 days.

A ford tech suggested me to use CHEVY yes CHEVY grease special order.
its a special lubricant it was used MOST of their Isuzu in past and it works really WELL so i applied it some in and so far its been good! The part # 12345718 its small blue can but pricy!! about 25 bucks shipping. you can order it on www. gmpartsdirect . com

If it fail again then last i ll try use marina boat grease.

YOMAN!

 

You know, Ford has been experiencing this clunk for over 10 years. You'd think they could engineer their way out of this. We're not talking about building a space shuttle - just a drive train clunk caused by a known issue.

Unbelieveable.

CMOS

 

I have the same issue now, and I have an open rear end differential (soon to change).

I'm gonna take it in tommorrow as this really pisses me off.

 

I had my fly wheel replaced on my 2005 FX4 super crew 5.4 ltr. About a week after I got it back I began to notice the double clunking that everyone is refering to. It almost felt like something was rolling back and hitting my tail gate when I accellerated. Anyhow after reading this thread as well as some others I decided to take the drive shaft and slip yoke off myself. I regreased the U joints and packed out the slip yoke with Valvoline Grease. It has now been over 100 miles and no sign of the double clunking. FYI the truck had 115,000 miles on it when the clunking began. Hope this helps!

 

i have had the same shuddering problems with my truck

i replaced the clutch paks and the problem went away... if u do that and have them add a bottle of friction moddifier you should be good to go...