U joint troubles

[Austin86250]

Alright, at a loss for words tonight
86 f-250 6.9T t-19 2wd carrier bearing drive shaft
Back in August I shattered the front u joint cap thought it was one off but tonight I sheared the strap
Both times where 3-4 down shift
After the first failure I put in a slicer u joint and I am meticulous about inspecting it every sunday and greasing it every 2500 miles
So I knew as of yesterday the straps where tight
I’m going to take the driveshaft to a driveline shop to have it fixed as it’s pretty dented now but fear there may be an underlying issue here

 

[ihc1470]

May not be any of what I list. U-joints in proper phase? Running at correct angles? Slip joint is free to slip drive line not to long or short? Maybe not of the above.

 

[Cant Write]

What about drivetrain mounts, engine-trans etc. coupled with the comments above?

Is it a harsh downshift from 4-3 causing it?

Would a 1-piece be an upgrade? Way too expensive..? Does t answer your question. Good luck!

 

[u2slow]

Are the little ujoint cap 'stopper nubs' still in the yoke? If not, the caps will work themselves out. Is there fore/aft endplay in the trans? (Pull yoke in and out)

Is the d/s support bearing inline with the trans and pinion? (Laterally)

I suppose the shaft is bent now... but was it already bent?

Most of my trucks in the past 25 years have had 2-piece rear shafts. No real issues.

 

[Black dawg]

Most repeat failures that I have seen when u bolts are involved is overtightening.
Is this 1330 series, and if so, ford almost always uses the big cap 1330 in positions with a u bolt yoke.

 

[Austin86250]

Old picture before any damages
But shows how good the angle is

 

[Austin86250]

Heard perhaps it’s a yolk issue?

 

[Black dawg]

What part number is that u joint? Doesnt look like any spicer joint I have seen.

Are the caps bigger where they bolt into the trans yoke vs the driveshat ears?

 

[Austin86250]

Oh no that u joint is my spare I had to throw in
they are the same size

 

[Rdnck84_03]

From what I can see in the photos everything looks pretty good. If everything feels and looks good, my guess would be that the ubolt had a stress crack that just gave up.

Could have been caused by the previous driveline failure or years of being over tightened or not evenly.

You would be amazed at how many of these I have worked on that people only tighten one side. The nut will be flush or less on one side and they draw a 1/4" through on the other side. If that has been done repeatedly it will cause cracks in hardened fasteners.

This may not be the cause but something to consider.

James

 

[XOLATEM]

I'm with the stress fatigue crowd on this one...

Those U-clamps can take only so much before they will yield...although it is surprising how much they WILL take...and not give you any indication they are stretched...unless you measure them before and after...

And...it is possible to crack a cap by over-tightening...

I don't know what is the recommended torque on those...but...if it is a 5/16" on the threads...I would estimate around 25 lbs-ft and no more than 27...

X2 on the 'evenly' pulled up...but I am kinda persnickety on that sorta thing...

 

[Austin86250]

I’m not sure how call are getting torque wrenches on these, well I guess crowfoot? My tools haven’t advanced that far yet
I believe all my yolks are still good so hopefully they can just retube it instead of make a new one
I assume the 2 piece driveshafts ain’t cheap
Too bad the 155” wb 6.9 2wd t-19 driveshafts are no where to be found at junkyards
Y’all think these straps are over kill or a good idea?

 

[Nero]

Not sure about the strap, but as for torquing them, use a dogbone socket

You must be registered for see images attach

 

[tbowker]

70 bucks for two straps sounds higher than the balls on a moose. Just my opinion.

 

[Austin86250]

Not sure about the strap, but as for torquing them, use a dogbone socket

You must be registered for see images attach

Does it reflect equal torque value?