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Discussion Starter · #1 ·
2002 cc, lb F-250 7.3L, 267k miles w/6” fabtech lift.
I was on my way to work the other morning cruising at around 65mph. Not under crazy acceleration, I start feeling an extreme vibration. Extremely extreme. Thinking I blew a tire or a suspension component I pulled over, engine running and to my horror found my transmission fluid making a mass exodus. Never seen that before. Immediately shutdown the motor and called a wrecker. Still being optimistic and knowing that the simple explanation is usually the right one I start searching for a blown Transmission line or fitting, what I found was much worse. I have a crack running clear across the transmission case, from passenger to driver side about 4” in front of the rear flange to the transfer case. Definitely NEVER seen that before. Upon closer inspection I find the transfer case to drive shaft u joint has also catastrophically failed.
So transmission: she’s a goner
Transfer case: condition unknown
Driveshaft: I know better than to try and fix it (yokes misshapen, chunks of cast steel missing)
Thankfully I’ve found a decent used 4R100 for a reasonable price and she’s sitting in my garage ready to go in tomorrow morning, still working on a driveshaft. My big questions is how? How did this happen. I’ve owned the truck for a little over a year (she came lifted) and logged roughly 20k miles in that time a lot of it highway/ light towing. Sometimes through mountains. I regularly check out my driveshaft and keep up a good maintenance routine. My U joints were by no means bad, at least not compared to some of the messes I’ve seen out there. To the best of my understanding this was caused by vibration in the driveline, now I have no earthly idea where it came from and that bothers the hell out of me. Could my center bearing be improperly shimmed? Did the U joint cause the transmission case to fail or did the transmission case cause the U joint to fail? Could the transfer case have something to do with this? It is full of oil and runs smooth for me in 4X4. Long post I know; but if you made it this far hopefully you have some insight, any help is appreciated
769264
769265
 

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that's impressive
either tranny locked and the sudden stop took the ujoint but that wouldhave been noticeable slam
or ujoint went and lodged between yoke and caused the drama .. you can see the sheet metal wound

u joint cross does not look dry
 

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so re reading your analogy it looks like we are of the same mindset
i see no real reason for this but I would have to suspect the yoke came before the egg lol
 

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I've heard a bad trans mount can do that.

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Discussion Starter · #6 ·
It’s bizarre right? That U joint was in good shape I mean except for that whole “being destroyed” issue. There was never a loud bang, despite the impact to the body. My guess is it just couldn’t be heard over the chatter of the drive line coming loose. She shifted just fine into park from drive when I stopped and then into neutral to get her on the flatbed. That makes me think the internals are ok, relatively any way. I’m gonna put the old tranny in a shop to see if it can be reassembled in a new case. Even if it can’t maybe I’ll get some insight. 79jasper The mount did come apart on me when I was putting the crossmember back in today, add that to the pile.
 

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No way the cross can exit the yoke unless one of the bearing caps backs out -- the ends on the cross and the bearing caps(bottomed out) are the same width as the yoke ears
thinking you have a missing keeper ring?

EDIT, after looking at the picture more closely, that cross is too small for that joint
the combination of the length of the cross and the two caps has to equal the distance between the joint ears
easy way to tell is to do a comparative measure, remove the seals from the caps, then install onto the cross
measure the total length and then the distance between the snap ring grooves
they should be the same, minus a little for clearance
 

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Discussion Starter · #8 ·
Hydro, there was one cap ejected. The other stayed with the yoke. I highly doubt that the joint was the wrong size but I’ll look into it tomorrow. Right now there’s no way of knowing if the retaining ring was gone beforehand. I mean at this point I’m doing this 50% to get myself back on the road and 50% for science. 😂 I’m really starting to lean towards the transmission mount, which I now know was bad. I had the truck on the lift at work two weeks ago, did my L.O.F. Rotated the tires and gave the drive line a good shake down... everything seemed good. Never thought to try lifting the transfer case to see if the mount would move.
 

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Hard to tell by the picture, just was giving a description of how the joint fits together
I have seen the clips come out before, usually being installed upside down contributes to that

Were you getting vibration from the drive line before the failure?
 

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Discussion Starter · #10 ·
Hard to tell by the picture, just was giving a description of how the joint fits together
I have seen the clips come out before, usually being installed upside down contributes to that

Were you getting vibration from the drive line before the failure?
No worries man, Nah only a matter of seconds when it all cut loose.
 
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