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Hard Shifting

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Hey all, 2008 MKX and since i've bought it at 200k miles (currently 213k) the transmission does some specific things. It shifts HARD when going from D to R consistently. I don't know enough about the inner workings of transmissions but I'd wager there's something special about that particular shift because it's always the hardest one. Sometimes it'll slam when downshifting up a steep hill as well... give it more gas and more and more up the hill until it downshifts, and BOOM. The third condition I've noticed is if you slow down (like taking a turn at an intersection), when you get on the gas again it will buck (this may be a downshift?).  Finally, rarely it will fail to upshift completely. You'll ride out the entire gear, sometimes hang out in it for a while, and then it'll find the next gear. It otherwise is normal if you make no sudden pedal movements and drive it smoothly.

 

I've heard that the input/output speed sensors can do this, but I have never had the odometer read "- - - - - - " or gone into limp mode. I also heard that the electronic throttle body could fail, causing incorrect throttle positions signals, thus bad estimated torque values in the ECM, and hard shifts. Then there's the whole "adaptive learning" portion of the trans, and of course failing shift/pressure solenoids. My question is, does anyone know how to diagnose or at least rule out some of these things? I just bought an automotive oscilloscope so I'm able to read the 'front door' sensor data from any of the above. Interested in what I should attack first, or any information at all that can lead me in the right direction without blindly replacing parts 😛

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Nobody...? I have some wiring diagrams. I can locate the signal wires on both the throttle position sensors, signals on the 3 accelerator pedal position sensors, and the signals from the input and output shaft speed sensors (the ones in the trans that always go bad). The goal is to view the signals for any obvious issues, and try to view each during the bad shifting events. Today it was 30 degrees this morning, and the entire length of my street it wouldn't upshift. I'm going to double check fluid, but I feel like this is an electronic issue.

2019-11-08 21.49.07.jpg

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If you're on Facebook I'd suggest you check out the MacT Ford Edge group.  There's been a lot of discussion about the TSS and OSS transmission sensors and how to replace them (use the search).  Those sensors are blamed for hard or erratic shifting, particularly for the Gen 1 Edge.  Here's a link: https://www.facebook.com/groups/MACTFORDEDGE/

 

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At 200K+ miles, we really would like to know the maintenance history on both engine and transmission.  Especially transmission fluid, but also plugs/coils/pcv valve etc.  A whole lotta problems stem from just OLD fluid, and it is a cheap/easy place to start your diagnostic.

 

Check the torque mount on the transmission, but that hard shift from D to R, assuming a complete stop prior to shifting, is likely to be the solenoid body assembly.

Edited by WWWPerfA_ZN0W

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Service history? I wish I could give it to you lol Like I said, I bought it at 200k miles from a used car dealer. I did plugs recently (about 2k miles ago). I plan to do a drain and fill soon, I can report back fluid condition. Hopefully that's the issue, but I'm a bit skeptical. Easier to start with fluids though, good suggestion.

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