2019 GT a10 random very hard downshifts at highway speeds at WOT

[speedup]

Not sure if this is 'normal' or not. My 2019 GT with a10 will sometimes downshifts really hard at wide open throttle at highway speeds in regular drive "D" mode (not sport/sport+). It harsh to the point that it almost feels like I have been rear ended. It doesn't do it all the time which is the frustrating thing, it probably wouldn't do it if I brought it into the dealer.

anyone else experience this? car has about 17k miles on it, and its done it pretty much as long as I can remember having it.

The tranny temp gauge never goes over 200 degrees, and the level is fine (i added a half of a quart a year ago to fill it all the way)

any help or advice is appreciated

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[compprep]

Read this thread. Only 28 pages! Must be something in here to address the issue.

https://www.mustang6g.com/forums/th...tions-to-harsh-or-no-shift-conditions.135463/

 

[The Demon]

I would read that thread as well but my 2019 A10 does not do that. Especially in non sport mode. Is it doing it on its own or when you brake?

 

[speedup]

Is it doing it on its own or when you brake?

It does do it sometimes when breaking, like when coming to a light, the last downshifts before stopping you really feel. Its not all the time, and it doesnt seem to be getting worse, it just is what it is.

still love the car tho lol

 

[gmupatriot]

Not sure if this is 'normal' or not. My 2019 GT with a10 will sometimes downshifts really hard at wide open throttle at highway speeds in regular drive "D" mode (not sport/sport+). It harsh to the point that it almost feels like I have been rear ended. It doesn't do it all the time which is the frustrating thing, it probably wouldn't do it if I brought it into the dealer.

anyone else experience this? car has about 17k miles on it, and its done it pretty much as long as I can remember having it.

The tranny temp gauge never goes over 200 degrees, and the level is fine (i added a half of a quart a year ago to fill it all the way)

any help or advice is appreciated

Read this thread. Only 28 pages! Must be something in here to address the issue.

https://www.mustang6g.com/forums/th...tions-to-harsh-or-no-shift-conditions.135463/

@speedup Once you go the the thread posted by @compprep go to my post #403. I had similar issues with my transmission. Turns out the transmission output shaft speed sensor was the issue. The dealership replaced the sensor and 6 quarts of transmission oil and my car has been running great since.

Good luck

 

[speedup]

@speedup Once you go the the thread posted by @compprep go to my post #403. I had similar issues with my transmission. Turns out the transmission output shaft speed sensor was the issue. The dealership replaced the sensor and 6 quarts of transmission oil and my car has been running great since.

Good luck

thank you for the feedback... one thing I noticed is my build also came with stock 3.55 gears.. could the hard 'downshift' be something in the differential?

 

[codereddew]

Stock tire size?

 

[speedup]

Stock tire size?

yes, car is all stock, still on the OEM tires

 

[Cobra Jet]

@speedup Once you go the the thread posted by @compprep go to my post #403. I had similar issues with my transmission. Turns out the transmission output shaft speed sensor was the issue. The dealership replaced the sensor and 6 quarts of transmission oil and my car has been running great since.

Good luck

I also recommend reading through the 10R80 thread too… it contains a great deal of info and very good responses from other S550 10R80 owners who give real world input to their experiences.

If it’s not the output shaft speed sensor, it could be the valve body which is also known to cause the “hit by a car” feeling. If the valve body line pressure is too high, the driver will experience those shift issues.

Make a service appointment. Request that the Service Writer, a Tech or Shop Foreman comes on a drive with you BEFORE you leave the car so that you can demo the issue if you’re able to replicate it. Otherwise if you just drop it off and tell them about the issue, you may end up with the “we couldn’t replicate the issue” when you go to pick it up…

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