Feels like someone rearends me!

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cobesgt

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Sep 20, 2019
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Location
Asbury, Iowa
Hello all, new to the Raptor forums. I'm a hands-on guy that tries to fix everything himself and this isn't my first rodeo working on vehicles.

OK, I bought my Raptor about 5 months ago. It's a 2010, 86K miles in great shape. Bought it from a private owner in Kentucky and drove it back home to Iowa. Noticed a couple groans and some slight clunks on the way home but figured I'd figure it out once I got it home. had to replace all Shocks with rebuilt units. Once I started driving it more I narrowed it down a little, I would come to a stop and as I was completely stopped it felt like it would downshift late, a bang like something hit me in the rearend. Upon further searching I found the slip yoke clunk, so I greased that with the Ford grease and the groan went away, but the aggressive bang didn't. As the temps have gotten colder here, it seems to be worse, but the more you drive it (stop and go traffic) the better it gets and almost completely goes away. Also, if I'm coming to a stop and shift to neutral, you can feel the bang as something disengages prior to the stop. Or as I'm coming to a stop I manually downshift to 3rd or 2nd or 1st, the bang doesn't happen. This only happens when I'm in Drive. Below are a list of all the things I've done to try to figure out this problem.
  1. Changed transmission fluid/filter and checked for latest software, no change
  2. Had TCM memory dumped and new shift points learned, no change
  3. Removed leaf springs/shocks/rear axle and checked all bushings/bolts/etc., no change
  4. Removed driveshaft and drove in 4WD, NO BANG! Appears to be something in the rearend binding-up, releasing and forcing the driveshaft forward.
  5. Replaced rear diff fluid and visually inspected gears/splines, etc., no heavy metals found and fluid looked OK, no change
  6. Replaced transfer case fluid, no heavy metals and fluid looked ok, no change
  7. Removed rear ABS Sensors and drove, no change
  8. Removed electronic diff lock connector, no change
  9. Removed rear brake calipers, no change
  10. Drive with traction control off, no change (but it does seem like it's not as bad)
  11. Drive in different off road modes, no change
  12. Replaced slip-yoke with new nickel plated type and added ford grease, no change
  13. Probably forgetting something that amounted to no change in the symptom.
At this point I really have no freaking clue what is causing this issue. Starting to wonder if this is the clutch pack in the diff locker and as the fluid warms the clutches slip easier. One last thing that happened this weekend. I pulled away from a stop and got on it pretty good (up to about 60), as I let off of the gas the RPM's stayed up and the engine rev'd some and then all of a sudden something released or shifted and holy hell, I thought the rearend or driveshaft or transmission was going to be behind me on the street. Anyway, if anyone could add some insight or next things to check, that would be awesome.
 

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