6R80 Problem

[FlaggedforHolden]

I just purchased a 2014 Mustang GT that had a procharger already installed. The car had a bad auto transmission that I had replaced. I’ve got about 200 miles on the new transmission. Today while driving on the freeway, the car downshifted violently for no reason. It was like I slammed on the brakes. The car skidded a little and I was almost rear ended. I pulled off the freeway and the car was stuck in 1st gear. I turned it off and then back on and it ran fine. I had my tuner return the transmission tune to stock and it drove home fine. Prior to this, the transmission would seem to downshift around town or not want to go into first gear from a stop and the speedometer would go to zero or bounce up and down. My mechanic is not sure what is happening. Anyone else experience something similar and if so, did you figure out a remedy? I am not at all mechanically inclined so I am learning as I go. Thank you in advance for any advice.

 

[Robert Larimer]

I just purchased a 2014 Mustang GT that had a procharger already installed. The car had a bad auto transmission that I had replaced. I’ve got about 200 miles on the new transmission. Today while driving on the freeway, the car downshifted violently for no reason. It was like I slammed on the brakes. The car skidded a little and I was almost rear ended. I pulled off the freeway and the car was stuck in 1st gear. I turned it off and then back on and it ran fine. I had my tuner return the transmission tune to stock and it drove home fine. Prior to this, the transmission would seem to downshift around town or not want to go into first gear from a stop and the speedometer would go to zero or bounce up and down. My mechanic is not sure what is happening. Anyone else experience something similar and if so, did you figure out a remedy? I am not at all mechanically inclined so I am learning as I go. Thank you in advance for any advice.

I doubt the Transmission you got was new. If it was you should have a warranty from Ford and you need to contact them. Modern automatics like the 6r80 are complex mechanical devices combined with complex software. Only mechanics familiar with this transmission would have a chance at knowing what is wrong. What happened to you was quite scary and I would try not to drive it until you fix what is wrong. Have you checked for error codes? That is something you can do.

 

[FlaggedforHolden]

You’re right, the transmission isn’t “new,” but it is remanufactured. I definitely won’t be driving it on the freeway until we figure out what is wrong. Someone suggested that I possibly have a bad speed sensor so I’ll have that checked out as well. Unfortunately there are no codes showing currently.

 

[JEWC_Motorsports]

Sounds like your tuner had it set up wrong.

 

[Dino Dino Bambino]

Sounds like your tuner had it set up wrong.

I'm inclined to agree. This sounds very much like an electronic control problem rather than a mechanical one.

 

[FlaggedforHolden]

JEWC_Motorsports, are you saying that the issue with the shifting and speedometer could be due to the tune being set up incorrectly? And if so, would the stock set up possibly fix the problem? I’ve only driven it about 25 miles since he changed the transmission tune back to stock and it has been fine so far, but I also drove the car 60 or so miles yesterday without a problem so I am not convinced it is fixed yet.

 

[JEWC_Motorsports]

Yes. The 6r80 does funky stuff when not tuned properly. If it's on the stock tune and works as intended I'd find a tuner that knows what he is doing with the 6r80.

 

[FlaggedforHolden]

I found this information and although it’s not regarding Mustangs, this is what happened to me. So perhaps the problem is the OSS sensor?

Safety recall for select 2011-13 Ford F-150 vehicles with 6-speed automatic transmission shift issUes

Ford is issuing a safety recall on select 2011-13 Ford F-150 vehicles with 6-speed automatic transmission that may experience an intermittent loss of the transmission output speed sensor signal to the powertrain control module, potentially resulting in a temporary, unintended downshift into first gear.

Depending on vehicle speed, a downshift to first gear without warning could result in a loss of vehicle control, increasing the risk of a crash.

Ford is aware of five reports of accidents, including one report of "whiplash" potentially related to this condition.

This action affects approximately 1.48 million vehicles in North America, including approximately 1.26 million in the United States and federalized territories and approximately 221,000 in Canada.

Affected 2011-13 F-150 vehicles were built at Dearborn Assembly Plant, April 28, 2010 to Oct. 28, 2013, and Kansas City Assembly Plant,

May 18, 2010 to Nov. 18, 2013.

Dealers will update the powertrain control module software in the affected vehicles. The Ford reference number for this recall is 19507.

§ media.ford.com

 

[Robert Larimer]

I found this information and although it’s not regarding Mustangs, this is what happened to me. So perhaps the problem is the OSS sensor?

Safety recall for select 2011-13 Ford F-150 vehicles with 6-speed automatic transmission shift issUes

Ford is issuing a safety recall on select 2011-13 Ford F-150 vehicles with 6-speed automatic transmission that may experience an intermittent loss of the transmission output speed sensor signal to the powertrain control module, potentially resulting in a temporary, unintended downshift into first gear.

Depending on vehicle speed, a downshift to first gear without warning could result in a loss of vehicle control, increasing the risk of a crash.

Ford is aware of five reports of accidents, including one report of "whiplash" potentially related to this condition.

This action affects approximately 1.48 million vehicles in North America, including approximately 1.26 million in the United States and federalized territories and approximately 221,000 in Canada.

Affected 2011-13 F-150 vehicles were built at Dearborn Assembly Plant, April 28, 2010 to Oct. 28, 2013, and Kansas City Assembly Plant,

May 18, 2010 to Nov. 18, 2013.

Dealers will update the powertrain control module software in the affected vehicles. The Ford reference number for this recall is 19507.

§ media.ford.com

So now the question is why didn't your transmission get the software update? Remember that tunes do not rewrite the entire software library they just make mods to certain parts. Also I am not sure that software for a 6R80 designed for an F-150 would work correctly in a Mustang without some mods. I would try to find out what that update did and make sure you have it. That might be problematic I'm afraid. But at least you know it is not a mechanical problem and your rebuilt trans was out of an F-150.

 

[gbstang]

I am going with the tune as well.. Verify the year of your 6R80, then go from there with your tuner..

 

[JEWC_Motorsports]

I am going with the tune as well.. Verify the year of your 6R80, then go from there with your tuner..

Good point. The new transmission strategy needs updated if it is different than your old transmission. The solenoids have their own programming.

 

[FlaggedforHolden]

I took the car out yesterday and within 20 minutes it revved while trying to engage 1st gear from a stop three separate times and then at one point, it died on me. Cranked right back on, but still weird. Dropping it off with the mechanic again today for him to drive it for a day or two. Hopefully he can figure out what is wrong. The tuner’s only remedy was reloading the stock shift points. He was recommended as the best tuner in my area. I don’t know much about tuning etc., and don’t know if there is anywhere else to have my car tuned in my area.