1995 F-150 Flareside scab
5-speed M5R2
8in. front sus. 6.5 rear sus
35x12.50R15 General Mud Grabber

Okay quick background: About a month ago or so I pulled my tranny out to replace the internal slave cylinder right behind the clutch assy. I put a jackstand under the oil pan, pulled the crossmember out along with the drive shaft and lowered the transmission replace the slave cylinder and put all back together. However! after the repair I was getting terrible driveline vibrations as if my driveshaft was at the wrong angles (again). You can refer to my little write up about that a few months ago. But the angles are identical to how it was before the pull. I then replaced both of my motor mounts and fixed my (cracked) crossmember hoping this would be the fix. Nope, still have the same problems, then I played the the L to R angle pushing it closer to the left side and testing it and gave up now I'm at loss and it bugging the hell out of me! PLEASE if you have any ideas let me know. Much appreciated!

 

Did you mark your drive shaft and put it back on in the same position?
Your u joints probably wore in in that position and then when you reinstalled in a different position( clocked ) it caused a vibration.
I would install new u joints in the rear drive shaft and start fresh.

 

Is it a constant vibration?? Any clunks or bangs??

 

first guess would be ujoints. but also need to know what was stated above, is it constant or does it come and go at speeds etc...

 

I replaced my ujoints not to long ago and my yoke on the axle side (flange type) was slightly bent to where I couldn't get the "c" clips in so I welded the cap to the yoke temporarily and I had no vibrations and no issues. So I haven't done anything to it since the weld.

I will eventually get around to it but thats not the issue because the u-joint is tight! Since its also lifted, the slip yoke on the tranny side is pulled out and i can wiggle it a little bit (hardly) but thats how it was before the slave cylinder fix and no vibrations. and that u-joint has less than 5k on it.

No I completely forgot to mark my driveshaft on the pinion flange..... and Yes I had considered this possibility and turned it once, but thats all. Maybe you're right and I should keep turning it.

No there is no clunks, bangs, etc. Only when I turn heavy and sharp the front axle passenger side will talk to me and tell me it needs some attention. but only thing is that my tranny has a slight slop in it and does my rear end but I haven't had a problem so far.



Oh and its at different speeds, slower is smooth faster is bad and Mach Turtle (pedel to the metal) is smoother than say 60-75mph. Coasting in nuetral is bad too.

 

I bet that's the problem. Try clocking your drive shaft again and again and maybe you'll find the sweet spot!!

This happened on my 92 5.0 4x4 when I put a new 5 speed in it.
Now I mark all my drive shafts before removal.

 

yeah I've done it every time prior to this but I had to do this at a nascar pit stop speed and forgot to take my time and mark that. I was told originally by a local tranny shop and I HAD it mark til I put a new axle under her

 

Ok I clocked it 180 degrees and nothing so far, il go 90 degrees and check that

 

Did the 90 degree clock and still nothing, I'll do another 180 and see the go to the other holes and check