emba129

Hi folks,
I have a 2015 Mustang GT / Automatic. It has 3.15 gears in the rear. I drive it daily to work. This is the first automatic Mustang I own and I have some questions.

As you know there are a few driving modes which change the personality of the car. Mostly, I use Normal and there is Sport and Sport Plus. I spend most time in Normal mode since its a daily driver but I am not really happy with the shift points in the 5.0 GT. in Normal Mode. It always goes for 6th gear, even around town. At 40MPH the engine is cranking around 1200 RPM, which is annoying when bumping slight throttle to accelerate. Is feels “boggy” unless I push the accelerator to kick down, which is too much. I say it feels like my grandfathers Oldsmobile!!. At 50 MPH cruising I oftentimes switch to manual mode and hold it in 5th which is more responsive. I added a Sprint Booster V3 for improved throttle response, which helps. But it doesn't stop the fact that the tranny searches for 6th at low speeds no matter what. When I go to Sport or Sport + Mode it wakes up a bit, but holds in lower gears too long and downshifts aggressively when coming to a stop. Its cool, but annoying when driving to/from work. Sometimes in Sport mode when I’m cruising down the highway at 65 it downshifts into 5th for really no reason, which I don't like.

I rent the Ecoboost l4 Mustangs on business trips and I really like those shift points. Its very responsive and shifts perfectly for zipping around town and on the the highway. These cars have same transmissions and likely the 3.15’s, as well. The car feels much more “drivable"

I been on the forums and spoke to Ford Performance about some options. Here is what they are and what was said:

- Can I put the Ecoboost tune it the 5.0 GT so it will shift the same?. Ford performance said not possible based on many different factors between the 5.0 and the turbocharged l4.

- Change the rear axle ratio from 3.15 to 3.55 or 3.73. I cannot see how the shift points would change, but higher RPMs would get the engine RPM up a bit which may make it more responsive. But the 3.15's are probably OK for the transmission gearing, especially 1st and 2nd which are pretty tall. And on long trips I really like the MPG I get with the 3.15s especially when I have cruise control set for 3 hours!. I don't really want to compromise that. Plus, does it really address the issue?

- Consider a custom tune. This could adjust shift points I think, but I’m not interested in hard shift points or aggressive downshifts like I see in Sport or Sport + modes. Im not looking for a drag strip tune or crisp, wheel chirping shifts. What I am only looking for is more responsive and better shift points and a better mapping for my daily drives, in Normal Mode. (like the Ecoboost Mustang). I don't want to keep shifting to manual mode. or pushing the pedal for downshifts just to have it go right back to 6th when I’m going for a gallon of milk!!

- Does a tuner from SCT/Bama help? Are there canned tunes or will these guys be able to help address the issue, which Im sure other Mustang enthusiasts have encountered. This ay I would get a tuner and be able to have more options for performance tunes as desired. Or are these tunes too generic to help.

Im trying to get an idea where to best spend the money to meet the objective.

Thanks folks.

wanted33

I wish I could help you with the top questions, but I'm sorry I can't. I will say any canned tune you put on the car will void your entire powertrain warranty. Just giving you some food for thought.

5.M0NSTER

I'd say go full CAI/Tune combo from Steeda or something along these lines, or just drive in sport mode.

I'm in 6th all the time at speeds near 45mph too, but all it takes is clutch in + throttle blip and a shift to 3rd to get gone.

woody24

I did a Steeda CAI and Tune from Brenspeed for my automatic 2006 GT. I loved how it shifted after that. At normal cruising, the shift points were nice and crisp, but weren't too aggressive. But put your foot down, and it was barking the tires up through 80mph.

BUT... I'm now pretty sure it may have destroyed my transmission over time. Last year, at 9 years of ownership, and about 7 years with the CAI and Tune, my transmission went out. The guy at the shop said he'd never seen anything so worn before, and asked if I'd been taking it out to the drag strip every week. Nope for the most part I was driving it like a daily driver. But might have gotten on it a couple times a week to be able to slip in a tight merge spot on the interstate. And that was about it.

But after just getting a 2017, I really miss the way my old one shifted. The '17 just feels sluggish. Even in all the driving modes to me.

So I'm in a predicament too. Keep it stock and keep the transmission safe, or risk that it may go out in 7-8 years and enjoy the hell out of the car until then?

5.M0NSTER

Well, I say drive it like you stole it. These cars love to be abused. Red line a day keeps the mechanics away.

The new trans has more gears than your 06 did, and it's rated for a lot more power too. So I wouldn't worry about it with just a CAI and tune. Good luck!

Bert

To the OP, I think you need a tune to take care of it; and you should be able to get the tune adjusted to shift the way you want, not overly harsh. I think I would probably talk to Brenspeed for starters.

And yes there is some potential to cause warranty problems; however the Ford aftermarket modifications troubleshooting guide was recently posted on another site and shows that the failure needs to be reasonably tied to the modification.

berzerk_1980

Before computerized transmissions, this was a fact of life with overdrive transmissions. In overdrive mode, the gearing was just barely enough torque to use cruise control on approximately level roads at highway speeds. We all trained ourselves to put the pedal to the floor briefly to force the transmission out of overdrive when passing or approaching a hill. It became muscle memory. So you might just find it's easy enough to get used to while your warranty is in force, then maybe go get a tune later to set the shift points where you want them for the different drive modes.

Also back then (1980s), and in many cars arrive then, most overdrive transmissions had a separate position that would turn off overdrive if you didn't want this behavior (at the expense of fuel economy). I've seen this in various incarnations over the years. My 1984 Impala had a D and OD position on the shifter, and my 2001 RAV4 had a button for "O/D off". Do you have anything like these?

Note, I have a '14 manual, so I'm not familiar with the peculiarities of the '17 auto. Apologies if I'm out in left field.

8905GT

So for the 2015 Mustang GT auto models, it is normal when in sports mode plus when the car is down shifting for the engine to rev up on every down shift?
This is the reason I do not like the sport+, I hate when I slow down for a stop light and every down shift my car revs then engine and the RPM goes up 500 so it is enging braking. I feel like everyone thinks I am trying show off my exhaust!
I just thought the sport+ mode was just not working correctly. I mean when it is down shifting like this I can feel the car jerk forward a little which makes stopping harder on my brakes~

5.M0NSTER

The car is helping preserve your tq converter. Yes, it should rev up for a down shift. In a well driven manual you don't feel a chance in decel, but that's because the driver adjusts over time to all the small factors that make the difference, like how worn the pads are, the sensitivity of throttle, the natural drag of drive train, etc. An Auto is programmed the same regardless and it is blind to many other factors, so some will drag more, some will make you fell like you're loosing decel.

8905GT

​​​​​​Hmm.. That's crazy, Today I was paying attention to my rpms on the down shift and it should go up 500-700 rpms! So annoying! Can't believe this is normal.

5.M0NSTER

Perhaps I'm not understanding your complaint. Are you talking about the 500-700rpm rev up on downshift, or the effect of it, like a surge forward when it occurs?

8905GT

Both, I don't like hearing my engine (exhaust) rev up every time I slow down to stop and I don't like how the car surges when it does down shift.

The car feels like a dog in normal mode and makes my axle backs drone since it always shifts in a higher gear.
​​​​​​Not sure what's worse. Drone and a slow car or annoying down shifting in sport mode. If this is normal I'll probably start using the paddle shifters exclusively.

SpectreH

- Can I put the Ecoboost tune it the 5.0 GT so it will shift the same?. Ford performance said not possible based on many different factors between the 5.0 and the turbocharged l4.
Ford is correct. You can't put the Ecoboost tune in. Apples to Oranges

- Change the rear axle ratio from 3.15 to 3.55 or 3.73. I cannot see how the shift points would change, but higher RPMs would get the engine RPM up a bit which may make it more responsive. But the 3.15's are probably OK for the transmission gearing, especially 1st and 2nd which are pretty tall. And on long trips I really like the MPG I get with the 3.15s especially when I have cruise control set for 3 hours!. I don't really want to compromise that. Plus, does it really address the issue?
Other than impacting mileage, the gear swap might be a good idea. I wouldn't go above 3.55, but that is just me.

- Consider a custom tune. This could adjust shift points I think, but I’m not interested in hard shift points or aggressive downshifts like I see in Sport or Sport + modes. Im not looking for a drag strip tune or crisp, wheel chirping shifts. What I am only looking for is more responsive and better shift points and a better mapping for my daily drives, in Normal Mode. (like the Ecoboost Mustang). I don't want to keep shifting to manual mode. or pushing the pedal for downshifts just to have it go right back to 6th when I’m going for a gallon of milk!!
A custom tune with altered shift logic might get you exactly what you want.

- Does a tuner from SCT/Bama help? Are there canned tunes or will these guys be able to help address the issue, which Im sure other Mustang enthusiasts have encountered. This ay I would get a tuner and be able to have more options for performance tunes as desired. Or are these tunes too generic to help.
I'd talk to Steeda or Brenspeed about a custom tune.
A canned tune might not get you what you want. Your's is the first complaint I've heard about the shift logic.

I will add that I like the logic in my '13 as long as I don't baby it. It would learn some bad habits if the car was driven too gently. Of course my '13 does not have all of the modes your car has so it is not a direct comparison.

5.M0NSTER

If you've driven a manual you know you're supposed to rev-match on down shifts. This will cause at least the noise if you're good at it, and noise and a surge(if too much throttle) or drag (if not enough throttle) if you're not.

During braking in a manual good drivers will heal-and-toe. Right foot on the brake, left foot onto the clutch, blip the throttle with the right wile braking, left foot off the clutch. When done right it's rewarding as hell and the engine rev sounds great with no change in decel. When not done correctly it's jerky.

Auto does the same thing. Except instead of a clutch the power goes through a torque converter. When lower gear engages it's got to be at the right RPM.

8905GT

Thanks for the thorough explanation. At least I know now it is Normal, Makes sense. To bad this is my first auto Mustang. I always driven a manual Mustang. An 89 and 05 GT. I would never down shift when slowing down to stop, I would always put it in neutral and coast and use brake to stop.

5.M0NSTER

No worries. I clearly don't know how bad the noise or jerk is in your car, and there may be room to improve by drivetrain/powertrain calibration.