2015 Mustang Ecoboost TRANSMISSION PROBLEM after Mexico trip

Slow92Vert

Member
Aug 8, 2019
22
11
13
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Walnut Park, CA
Hello Everyone,
I need some help.

2015 Mustang Ecoboost A/T with 40,000 Miles.

I went to Rosarito this weekend with 2 friends, and we decided to take my car. On the way back we where stuck at the border crossing for about 10 hours. So, there was a constant shifting from P-D and moving about 2 MPH for a couple of inches at a time. I must have shifted over 100 times.

Once we crossed and I was able to get on her I noticed a SLIPPING (3-4Gear) and a sudden clutch engagement (Feels like a hard shift).

The next day I took my soon to school and noticed more erratic shifting, 3-4Gear Slippage is mostly constant . However, that day while accelerating out of a red light (1stGear), the RPM's jumped really high but the car was barely moving, To me it seems like the car was at a higher gear, maybe 3rd.

Jump forward to today, I realized that my car at times does not completely downshift to 1st when coming to a stop, and that's what causes the high RPM's at launch from a red light.

I was able to stop that from happening by using the paddles to shift to 1st when coming to a red light. Also note that the 3-4 gear shift does produce a constant slippage and a hard engagement that feels like a hard shift.



Has anyone had this issue, if so can you please provide some guidance?
 
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90sickfox

I didn't really have an issue with the stink...
SN Certified Technician
Mar 2, 2015
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I haven't had that issue but I am a Master Mechanic and work for a dealer. Are any of your lights on on the dash....check engine...traction control ?

These transmission are hydraulic and electrically controlled. The first thing I'd do is schedule an appointment with a dealer for diagnostics. They will probably reflash the transmission control module. When they do that the transmission will go back through its learning strategy as you drive. ( drives a little weird ). If it's still slipping and hard shifting they'll tell you exactly what needs to be done.

You don't have to get the work done at the dealer but it's the absolute best place for a diagnosis. Warranted used transmission are available through companies like LKQ auto parts online.
 
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Slow92Vert

Member
Aug 8, 2019
22
11
13
32
Walnut Park, CA
I haven't had that issue but I am a Master Mechanic and work for a dealer. Are any of your lights on on the dash....check engine...traction control ?

These transmission are hydraulic and electrically controlled. The first thing I'd do is schedule an appointment with a dealer for diagnostics. They will probably reflash the transmission control module. When they do that the transmission will go back through its learning strategy as you drive. ( drives a little weird ). If it's still slipping and hard shifting they'll tell you exactly what needs to be done.

You don't have to get the work done at the dealer but it's the absolute best place for a diagnosis. Warranted used transmission are available through companies like LKQ auto parts online.
There where no fault codes or lights.

UPDATE. UPDATE. UPDATE.

My transmission seems to be back in normal working mode. All it took was a an open road and a heavy foot, and bam back to normal shifting.

Being on a budget, I was driving my ecoboost mustang really conservative. No heavy throttle or launches. Just a very light feather throttle on red lights. I believe that this might be the cause, "SUDDEN/CONTINIOUS CHANGE OF DRIVING BEHAVIOR".
 
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