Transmission drive train issue

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Emory

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Sep 23, 2019
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Location
Fredericksburg, Va.
So here is my second thread today. Vehicle: 2008 ST AWD 4.6 . At times, I may come to a stop and a nanosecond later I feel a "bump" in the drive train. Then sometimes I may be in a downhill sloping grade on the roadway with my foot basically off the gas (but not completely), when I increase the gas I might feel that same bump in the drivetrain. Don't think it's a U-joint. Other than this, the transmission shifts beautifully. NOTE: a couple of months ago, I came off the interstate to a stop light. When I began to take off, the transmission shifted up and down in a crazy fashion! I was close to an Auto Zone and pulled in to get them to scan for any codes. All we got was a bad mass air flow sensor. Bought a new one and installed it. Vehicle immediate cleared the code and shifted fine. Don't know if that sudden shifting up-down, etc, craziness has anything to do with this issue. Thanks for any comments!
 
If it is what I think it is - it's typical and unavoidable.

When I come to a stop, I generally feel it bump into 1st gear. It's typically mild to almost unnoticeable, but more noticeable when the transmission is fairly hot (205+) and certain kinds of hard stops.
Also, if I'm in 2nd or higher and put in neutral come to stop, I will feel a clunk around 4-5mph. This is the L/R clutch coming on - it's normally held in P/R/N/D(1)/1.

I've noticed that if I'm coasting in 2nd at around 8+ and give it a bit of gas, it chooses to downshift to 1st and that gives it a weird almost slip-bump feel.

In addition, the 1-2 shift always has a bit of a bump to it, mine is a little more pronounced when first driving in the morning and at low speeds where I slowly cross the transition from 1-2.
As I understand it, the 1-2 shift is the very quick sequence of:
-driving in 1st gear (Forward and L/R clutch engaged)
-tiny throttle dip (torque management)
-release of L/R clutch (now only forward clutch engaged)
-engagement of 2/6 clutch (forward and 2/6 engaged)
-throttle dip ended

Ford finally addressed these two bumps in the 2011+ 6R80 with a one way clutch and redesign to support it. No, there's no reasonable way to retrofit this into our models.
 
If it is what I think it is - it's typical and unavoidable.

When I come to a stop, I generally feel it bump into 1st gear. It's typically mild to almost unnoticeable, but more noticeable when the transmission is fairly hot (205+) and certain kinds of hard stops.
Also, if I'm in 2nd or higher and put in neutral come to stop, I will feel a clunk around 4-5mph. This is the L/R clutch coming on - it's normally held in P/R/N/D(1)/1.

I've noticed that if I'm coasting in 2nd at around 8+ and give it a bit of gas, it chooses to downshift to 1st and that gives it a weird almost slip-bump feel.

In addition, the 1-2 shift always has a bit of a bump to it, mine is a little more pronounced when first driving in the morning and at low speeds where I slowly cross the transition from 1-2.
As I understand it, the 1-2 shift is the very quick sequence of:
-driving in 1st gear (Forward and L/R clutch engaged)
-tiny throttle dip (torque management)
-release of L/R clutch (now only forward clutch engaged)
-engagement of 2/6 clutch (forward and 2/6 engaged)
-throttle dip ended

Ford finally addressed these two bumps in the 2011+ 6R80 with a one way clutch and redesign to support it. No, there's no reasonable way to retrofit this into our models.
I think I am experiencing the same thing with my 07 ST limited. I don’t feel any real noticeable bump on accelerating or driving. I only seem to notice it when coming to a slow stop. There’s that bump at about 8-10 km’s as you come to a stop.
Is this a transmission replace scenario or is there another solution? Thanks
 
In the early years, of the gen2 V8. Ford came up with a software reprogram for the TCM. It helped with some Trac's.
We had a few members back in the day, did this. Disconnect the neg cable then the positive cable. Touch the leads together. Not on the battery though. Some of them claimed it reset the TCM, to relearn.
 

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