Stutter between gear shifts under WOT

TSS · May 12, 2017, 10:15:55 AM

I personally don't notice any difference other than the lack of stutter. I already change my transmission fluid every 18000- 20,000 miles with the B&G service at the dealer. Also change the PTU fluid at the dealer regularly. That also had no effect on the stutter. The only thing that fixed it was the softer version shift tune.

Unlike Bruce, mine did it from day one of the tune. The only way to get rid of it was to put the car back to stock at that time. And recently, I inadvertently loaded the old version after service at the dealer. The first time I did a wide open throttle from a stop, I immediately knew I had loaded the wrong tune because the stutter was back.

I have not added any extra transmission fluid as was suggested at one time as a remedy. I just did not want to do that. I wanted to resolve the issue using the correct manufacturer specified volume of transmission fluid.

StealBlueSho · May 12, 2017, 12:36:19 PM

This answers my questions. No need to worry about PTU/Transmission stuff..... yet...... eventually the piper will get his payday...

16MagSport · May 14, 2017, 11:52:06 AM

What exactly does this stutter feel like? It isn't just hopping the front tires on the shift is it. Our Explorer did that with a hot tune. It felt pretty violent and I was worried about the trans holding up. It also detonated though so I didn't run the tune.

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StealBlueSho · May 14, 2017, 12:10:47 PM

Quote from: 16MagSport on May 14, 2017, 11:52:06 AM
What exactly does this stutter feel like? It isn't just hopping the front tires on the shift is it. Our Explorer did that with a hot tune. It felt pretty violent and I was worried about the trans holding up. It also detonated though so I didn't run the tune.

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It's not wheel hop, although it does feel similar...I would say it's wheel hop if I hadn't datalogged the event or had it happen on the 2-3 gear shift too.

On a side note... did a KAM reset after I loaded the standard 4+X Race tune... hasn't stuttered yet... temps are also in the mid 60s... now high 70's... gonna keep an eye on it...

Gjkrisa · May 14, 2017, 01:09:09 PM

Quote from: StealBlueSho on May 14, 2017, 12:10:47 PM
Quote from: 16MagSport on May 14, 2017, 11:52:06 AM
What exactly does this stutter feel like? It isn't just hopping the front tires on the shift is it. Our Explorer did that with a hot tune. It felt pretty violent and I was worried about the trans holding up. It also detonated though so I didn't run the tune.

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It's not wheel hop, although it does feel similar...I would say it's wheel hop if I hadn't datalogged the event or had it happen on the 2-3 gear shift too.

On a side note... did a KAM reset after I loaded the standard 4+X Race tune... hasn't stuttered yet... temps are also in the mid 60s... now high 70's... gonna keep an eye on it...

What did you select for logging?

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StealBlueSho · May 14, 2017, 01:14:15 PM

Torque Source...

16MagSport · May 16, 2017, 03:45:16 PM

What did the log show? Did the advance and/or throttle blade angle drop or swing wildly at the time, differently than a smooth shift? Sure sounds like wheel hope since it goes away with a softer shift. Did you feel torque steer on the shift as well?

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StealBlueSho · May 16, 2017, 08:55:41 PM

Quote from: 16MagSport on May 16, 2017, 03:45:16 PM
What did the log show? Did the advance and/or throttle blade angle drop or swing wildly at the time, differently than a smooth shift? Sure sounds like wheel hope since it goes away with a softer shift. Did you feel torque steer on the shift as well?

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Hmmm, well... LMS doesn't eliminate all of the torque management, so at shift there is a torque source of 7 I believe? Don't have the logs in front of me.. but it's the source torque for shift modulation... but this is at every shift... Brad utilizes it as well since it takes care of adjusting spark at shift as well.. this is what Brad has mentioned to me...

Also, LMS uses the throttle to manage load, the the throttle does quite a bit of dipping through out a run... mainly I am sure to help with fuel pressure and boost spikes...

Honestly, besides the slightly extended torque source reading, and the quick period where the RPMs stay flat... nothing out of the ordinary...

But it doesn't feel like traditional wheel hop to me... the front end isn't bouncing around etc... it just stutters like it's not fully engaged in the gear...also does it once in awhile from 2nd to 3rd... and there shouldn't be wheel there...

I run BFgoodrich Sport Comp 2 summer performance tires...sticky tires...plenty of tread life...

Since I have done a KAM reset, driven it normally with the occasional WOT trying to give the learning portion time to catch up it has not done it....so I dunno... it's also much warmer so that could be a part of it...

16MagSport · May 17, 2017, 12:47:46 AM

Much warmer means the tires are softer. They'll hook harder but if they do spin it may be smoother. Pay attention to the road conditions too when it happens. Some roads are stickier than others. Did you have torque steer? I know my wife's Explorer hopped and would jerk with torque steer. That tune had all torque management removed and huge boost spikes. Brad's is nice and smooth. I like that because I can go WOT with the fam onto the highway and it is smooth and I don't get yelled at. If it was hopping and jerking, the wife would be a little upset. I was disappointed that it did this hopping. The damn AWD should keep that from happening. If it was locked in a 50/50 power split then it couldn't hop the front tires. I wish it wouldn't let the fronts spin faster than the rears when at WOT.

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StealBlueSho · May 17, 2017, 12:45:33 PM

Quote from: 16MagSport on May 17, 2017, 12:47:46 AM
Much warmer means the tires are softer. They'll hook harder but if they do spin it may be smoother. Pay attention to the road conditions too when it happens. Some roads are stickier than others. Did you have torque steer? I know my wife's Explorer hopped and would jerk with torque steer. That tune had all torque management removed and huge boost spikes. Brad's is nice and smooth. I like that because I can go WOT with the fam onto the highway and it is smooth and I don't get yelled at. If it was hopping and jerking, the wife would be a little upset. I was disappointed that it did this hopping. The damn AWD should keep that from happening. If it was locked in a 50/50 power split then it couldn't hop the front tires. I wish it wouldn't let the fronts spin faster than the rears when at WOT.

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No torque steer that I can remember. I am fully aware of the difference between cold tires/road vs warm tires/road...different types of asphalt etc...

Thanks!

TSS · May 17, 2017, 06:48:43 PM

The stutter feels like the car tries to switch gears but misses it (doesnt catch)on the first or second try. I know that's not very descriptive, but it's an awful feeling that makes you think something really bad is happening.

StealBlueSho · May 17, 2017, 07:46:15 PM

Quote from: TSS on May 17, 2017, 06:48:43 PM
The stutter feels like the car tries to switch gears but misses it (doesnt catch)on the first or second try. I know that's not very descriptive, but it's an awful feeling that makes you think something really bad is happening.

Yea, like your stop is gonna be a transmission shop...

16MagSport · May 17, 2017, 10:23:09 PM

Strange. If you didn't feel anything in the wheel then it wasn't hopping. Well, I would just run the softer shifting tune and not worry about it. Hopefully it just means that it is unhappy with that higher pressure. Makes you kind of wonder if the pressure should be dropped more for some safety margin.

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StealBlueSho · May 17, 2017, 11:52:43 PM

Quote from: 16MagSport on May 17, 2017, 10:23:09 PM
Strange. If you didn't feel anything in the wheel then it wasn't hopping. Well, I would just run the softer shifting tune and not worry about it. Hopefully it just means that it is unhappy with that higher pressure. Makes you kind of wonder if the pressure should be dropped more for some safety margin.

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Well... who knows right? I know they dial up the transmission shift speed and pressures to very edge... I believe that is self evident with some who can run it and some who can't...

If they are pushing it to the point where mechanical tolerance between builds makes a difference then maybe there is something to be said about running on the ragged edge...

BUT... if say 85-90 percent of the cars can run it without problems and there is enough advantage to running the tune that way... the other 10-15 percent are just gonna be anomalies you deal with...which means taking it to Ford to get a new transmission and/or PTU may NOT solve the issue..

For me personally there is NOTHING to indicate there is a mechanical deficiency in my car... no codes, fluids look good, shift great on other tunes or those with a slightly lowered pressure...

I will say with the rise in temps to an average of 70F along with the KAM reset I have not had an issue yet...

Brucelinc · May 18, 2017, 09:27:07 AM

The stutter has been described as the car attempting to shift - not shifting - attempting to shift - not shifting and then shifting - all of this in a split second. It is a bit of a mystery why some cars do it with high shift pressure and some do not. It is also odd that in several cases, new fresh fluid eliminates the issue and in other cases, it has no effect.

As Todd and I have both confirmed, lowering the pressure to prevent it does not hurt acceleration.