Hi, everybody! long time reader, first time typer. I need help with a problem that I've never encountered before, and I hope that I'm in the right forum, (don't want to tick any moderators). I have a 94 f150 ext cab, and I just replaced all three u joints and the carrier bearing. -solved the squeaking, but since I had to separate the two driveshafts to replace the bearing, thus breaking the time fused union, the front driveshaft is wandering out of the back of the transmission, causing the backside of the driveshaft to compress into the carrier bearing and bracket. I also experience minor vibration as the yoke becomes unstable as it pulls out of the back of the tranny. is this system supposed to "float and return" or is it supposed to remain rigid? I have devised a way (using a short length of cut pipe between the two shafts) to keep the front shaft from migrating rearward, so that I can get back and forth for the time being, but I always get nervous when using this type of augmentive engineering. anyone know why this is happening, or even heard of this before?

 

The movement allowed for in the driveshaft design is only to allow for suspension travel. If all is well there should be only momentary fore and aft movement of the center bearing. My surmise is that the spline on the front yoke is going away causing it to work it's way backward. Pull the shaft and examine the inside of the spline. It may be hard to detect but I expect the you will find that it is worn. If it wobbles on the output shaft replace it. In most cases the output shaft will be made of a harder steel than the yoke, but look at it anyway.

 

Is there any way you have the drive shaft installed bassackwards?
The front portion should not move.

 

...Welcome Jeff to Ford Truck Enthusiasts!

…..See you on the boards.

 

back assward? - great one, Stuart! no sir - I dont beleive that I could put it in backward if I tried. The shafts are different lengths and I marked all of the yokes to avoid balance troubles, pressed everything off and on so as not to damage anything, and had an extra set of arms throughout the entire process. the front shaft is moving backwards out of the tranny, tightening the space between the carrier (center) bearing and the zirc for the grease fitting on the rear shaft. I also forgot to mention that it is only two wheel drive, and that both shafts in question are behind the transmission.


Bdox - it is highly possible that the front yoke is damaged. although I've had this truck for eight years, I did get the truck used, and even though I've never had any troubles with drivetrain vibration, it's not to say that there wasn't a problem before I got it. that would make sense as to why I only noticed it after I freed the two shafts from one another. Thank you very much, sir, I will drop the shaft and inspect it immediately! I don't wanna sound dumb, but is the yoke available at parts stores, or will I have to do the dealership/junkyard thing? and by the way - I'd like to say thanks for the warm welcome and that all you guys kick ***! Thank you both very much- Jeff

 

-oh, and thanks for the welcome, Tim!