Friend claims he controls the shift points of automatic Mustang GT by using throttle

[sugarwood]

He said:
In a straight drag race with an automatic transmission, you get a great start and let the transmission take care of the rest by hitting the redline in each gear. It’s basically idiot proof. I consistently have the transmission shift around 3500 for daily driving. If it’s spirited driving, 4500 at the max, any more and your just spinning it, which is pointless if you’re not drag racing.

I said:
Wait, how do you have control over the shift points with the auto ?

He said:
Throttle. I look at the tach far more than I look at the speedometer.

I said:
Never heard of this capability in any auto car.
If you want it to shift at 4500, what do you do differently with the throttle ?
(compared to what you do if you just let it shift at factory preset 3000)

He said:
Push the throttle lower and it’ll rev higher. I can get it to shift at any RPM below 6000 I want just based on my muscle memory of the location of the pedal.

I said:
Interesting. You need to show this to me. Every auto car I’ve ever driven shifts at a fixed RPM, regardless of what you do to throttle. If the car is programmed to shift at 3000, you’re saying you give more throttle? In my experience, all that does is make the car reach 3000 sooner, and then it shifts at 3000 anyway.

He said:
By that logic, flooring it would cause it to only rev to 3k in each gear, instead of redline, wouldn’t it? That’s definitely not the case in the three Mustangs I’ve driven. The car only shifts at 3000ish if I drive it like a typical driver, which is almost never. I know a lot of drag racers like to use automatic transmissions because it can shift faster than a driver can if there’s a significant amount of power. There is more control in turns with a manual transmission, but I can drive better and hold my own with an automatic because of my bum left leg. I’ll take you for a ride whenever you’re up to it.

I said:
Yea, that’s exactly what ever auto I’ve ever driven does.
If I FLOOR the gas on a straight way, and never lift my foot, it will still shift at 3000 in every gear.



Again, he is not talking about simply mashing the gas pedal in order to induce a downshift. I never knew this was possible. What is this called ?

[stomachmonkey]

Auto trans are a lot more complicated today.

They combine input from a variety of sensors.

It's not unreasonable to think you can't work out various TPS and WSS scenarios that would affect shift point.

But I don't think that is using the trans to it's potential.

[mattdavis11]

True stuff. The only way I could bark the tires on the dodge p/u 318 w/ 727 torque flight was to make the tranny shift when I wanted it too. I'm not talking about manually shifting it, just mash the pedal, let off, hammer the pedal, chirp.


Same goes for every automatic I've driven. I've never driven an auto that always shifts at a certain RPM. My Land Cruiser will hit final gear at 51mph, but not if I have my foot in it.

[Jrboulder]

My 2002 ford explorer was like that. Getting on the freeway at WOT the shift point was almost at the redline. Around town it was much lower. I thought all automatics were like that?

[masraum]

Originally Posted by sugarwood

I said:
Interesting. You need to show this to me. Every auto car I’ve ever driven shifts at a fixed RPM, regardless of what you do to throttle. If the car is programmed to shift at 3000, you’re saying you give more throttle? In my experience, all that does is make the car reach 3000 sooner, and then it shifts at 3000 anyway.

What? I've never had an auto in any vehicle that had fixed shift points. Every auto car that I've ever had has varied the shift point based on throttle position, even more so with modern computer controlled cars.

In my experience, you you are very light on the throttle, it'll shift at very low rpms, if you are more moderate on the throttle, it'll shift at mid-range rpms and if you are heavy on the throttle it'll go to high rpms until full throttle means redline. I've never had any auto car work differently.

[MysticLlama]

I've never had an *old* car, but even my 1980 Thunderchicken shifted like that, as has every auto I've ever had.

Give it more gas it holds the gear longer.

A fancier example, the '02 M3 SMG adjusts how fast it shifts gears when called for and then actuates the clutch at different speeds based on throttle position.

I think the auto working how he says is totally normal.

[mikesride]

Be pretty hard (and dangerous) to try and pass anybody if your car always shifted at 3K.

[gduke2010]

They always called it passing gear?

[Jeff Higgins]

Sugarwood, I'm afraid you are confused. The answers above pretty well outline how automatic transmissions behave. There is nothing magic about your friend's driving technique, nor anything special about his car. No automatics I'm aware of are "programmed" to always shift at the same rpm. The shift point is throttle position and load dependent. In the old days, this was accomplished with linkage between the carburetor and transmission working on an internal valve body in that transmission. Today it's all pretty much electronically controlled and is far more precise as a result. The effect is the same, though, with the shift point being tailored to the demands being placed upon the engine. It's always been that way.

[wdfifteen]

Originally Posted by sugarwood

You need to show this to me. Every auto car I’ve ever driven shifts at a fixed RPM, regardless of what you do to throttle.

I've never had an automatic that behaved that way. Shift points are determined by speed, throttle position, load, engine coolant temp, and probably a lot more data points.

[Noah930]

Originally Posted by mattdavis11

True stuff. The only way I could bark the tires on the dodge p/u 318 w/ 727 torque flight was to make the tranny shift when I wanted it too. I'm not talking about manually shifting it, just mash the pedal, let off, hammer the pedal, chirp.


Same goes for every automatic I've driven. I've never driven an auto that always shifts at a certain RPM. My Land Cruiser will hit final gear at 51mph, but not if I have my foot in it.

Agree with Matt. My first car as a teenager was a '75 Benz. Even in that car, without modern electronics, it was the same technique: floor it (or at least accelerate aggressively) to hold the gear, and when you want it to shift to the next higher gear, just breathe the throttle a crack (slush box will shift up) and immediately get back on it.

[ckelly78z]

In my Diesel Ford truck, when pulling a heavy load, it sometimes wants to linger in the 3000 RPM range. I often lift off the throttle for a second to make it shift into the next gear thus getting into the meat of the torque curve (1500-2500 RPM) and it will acceleate faster at lower RPM. I don't know that this applies for higher revving gas motors, but it does on the diesel.

[911SauCy]

I can see it being true in the case of a 727, where shifting is predicated by hydraulic pressure influenced by engine RPM.

However, I'm not totally buying it with a new car. As mentioned, there are a lot of electronics an computers at play, and most cars entire power trains try to learn your driving style now. Perhaps that just it, he and the car are in great tune with one another.

Heck a human designed it, so why couldn't another human manipulate it?

Or...you can just use the stick in the console, called a shifter. Almost all auto cars now have some laughable version of tiptronic, manumatic..autocrapbomb etc

[jyl]

Even old US slush boxes will delay upshifts to higher rpm if you are at WOT.

[flipper35]

Our 2014 will vary the upshift depending on throttle position so they still work off the same concept/principal but with different sensors providing the upshift timing. Also, a quick stab of the throttle will have the car downshift quickly even if you don't go full throttle. At least on ours.

It also says in the manual it learns the drivers and adapts from there.

[wildthing]

My minivan does that. It's a 2011. Not a smooth and fast shift, but shifts later if more throttle is applied, release and it shifts higher even more.

More fun on the VW DSG...

[gprsh924]

OP is either trolling us because be can't believe his friend seemed impressed by being able to make an auto trans shift at different RPMs or he has exclusively driven cars with broken transmissions.

[Norm K]

Originally Posted by sugarwood

I said:
Every auto car I’ve ever driven shifts at a fixed RPM, regardless of what you do to throttle.

Uh oh, better get AAMCO!

[Laneco]

I have old cars, middle-aged cars, and because I travel so much (like twice per month), I get brand new cars as rentals.

How many shift at exactly the same point regardless of throttle input? ZERO.

That includes basically all combinations of mechanical/hydraulic/vacuum control and fancy-pants new-school all-electronic. The shift points vary based on mode for newer transmissions (sport versus econo) and throttle input. That lets you mosey along in traffic with a low shift point for fuel economy or stay in the existing gear to at/near the redline for spirited driving.

angela

[sugarwood]

Ok, I must have had a case of distorted memory. The auto does shift at a much higher point at WOT. I must have been confused, since I have gotten so conditioned to every shift at 3000 b/c I am never at WOT when approaching 3k.

So, is it fair to say an auto is comparable to a manual gearbox for straight line drag racing (ignoring the fluid coupler torque converter inefficiency) and the real difference is navigating turns? His throttle technique can maintain high RPM in straight lines. But, when you slow down before a turn, an auto can't maintain high RPMs (lower gear) while giving zero throttle.