Again I must mention that we are going to address how this references Maseratis, very specifically, Maserati Gran Sports, Quattroportes, 4200’s, and the Gran Turismo S F1. But please also know this is applicable to Ferrari and E Gear as well, their systems are not that different, and many times use the same components. Some are in different positions and look slightly different but perform the same function.
Let’s start off with a basic description of what we have in these cars as a whole. First, it’s known as a robotized gearbox control system. It is not an automatic transmission, it’s not even “Automatic” like, just because it has an “Auto” setting. The gear-box is a standard transmission gear box, it has shift forks, and is identical to a regular 3 pedal (clutch, brake, and fuel pedal) car. There isn’t any difference. The real difference is you have the highly advanced technology, or a robotized gearbox control system controlling the physical movement of the clutch engagement, and the shifting of this car. The system is composed of an electro-hydraulic servo system which manages the gearshift and clutch operation.
There are about 6 parts to this system as it relates to the actual gear box, and how it shifts:
- 1.) Gearbox housing
- 2.) High Pressure pump, commonly referred to as the F1 pump or E Gear pump. We will pair this with the Hydraulic Reservoir. As the pump receives the fluid from this.
- 3.)Power unit. This is the 6 solenoid valves, pressure sensor, pressure relief valve, check valve, and bypass screw. (The heart of the system)
- 4.)Hydraulic Pressure Accumulator (It stores the hydraulic pressure created by the F1 pump similar to the way an air compressor tank stores the air from an air compressor pump.
- 5.)Hydraulic Gearshift Actuator (This literally changes the shift forks of the gearbox as the solenoids are fired for the different gear selections of the system).
- 6.)The NCR or the Gearbox control unit, that controls the complete system by using a strategy which is based on driver inputs and various vehicle parameters.
Today we are going to be focusing on the actual Hydraulic Gearshift Actuator itself.
The function of the Actuator again is to activate the gearshift forks in order to drive the gear engagement and selection movements. Basically what this does is shift the car like you would if you were in a manual transmission car.
So say for example, you are at a stop sign sitting in neutral in a normal standard transmission car, you push the clutch in, physically with your right hand (left for UK) you move the gear shift lever over to first gear. Well the part you cannot see as you do this, are the cables/lines attached to the side of the gear box pushing or pulling the gearshift forks in the direction it needs to go for the gear you are selecting or engaging. Let’s look at some photos as it’s applicable to these cars.
The top photo is a picture of the gearbox where the hydraulic actuator mounts to it. As you can clearly see the shift forks through the opening line up with the armature of the hydraulic actuator beneath it. In this example, both the actuator and gearbox are in neutral.
Parts of the Actuator
I do not know how clear the picture above is but I think it will be enough for a bit of an overview. The parts are:
- Actuator (there is actually two actuators that the diagram above doesn’t show)
- Hairpin Duct
- Gearshift Command Shaft
As the pressurized fluid is released by the solenoids it comes through the hydraulic high pressure lines to the top part of the Hydraulic Actuator. What happens here is the least understood about the Actuator itself. Now first of all I mentioned only one actuator is titled in the diagram above. That diagram wasn’t provided to show all the internal parts of an actuator. I will show more of that below.
Here’s another thing I need to mention. I am referencing the Actuator as a whole, or the Actuators’ housing/encasing and the individual actuators that provide the function of actuating when the pressure is supplied to those chambers. Please don’t be confused.
So let me see if I can show you the two actuators that are actually inside the “Actuator” or actuators’ housing, and explain them.
A quick look at the photos above. The two brass objects you see in the photos are actually the two actuator end pieces with seals held in with “C” clips. The colored diagram above only shows the smaller of the two. The smaller of the two operates the turning/rotating action of the gearshift command shaft through the hair pin duct. This controls the selection or clocking of the Actuator finger. So for instance, if you were in a three pedal car. This would be like you going from where the “1-2” gears are at in the middle of the shift gate to pushing it over one to where “3-4” are, or all the way over to where “5-6” are. You are selecting where you what the shift finger in the shift gate to be before you engage either of those gears. We will get really indepth with this below.
Now the bigger of the actuators not shown in the diagram, controls the actual engagement, it’s the horizontal movement that engages the gear shift forks in the gear box. Again we will get into this in-depth below but to follow our example above, you selected “1-2” or “3-4”, well this actuator moves the gear command shaft itself horizontally left or right to engage 1st or 2nd gear or into 3rd or 4th gear.
Above is a photo of the actuator piece they don’t show, the bigger of the two, in the diagram. It’s the one that has the hairpin duct attached to it as shown in the lower photo of the two.
The top photo shows two brass type end caps in the middle of the photo. You’ll see the outside seals that keep the pressurized hydraulic fluid in the chamber. This actuator is still attached to the gearshift command shaft, but it actually unbolts from it right at where the inner C clip is sitting in the top photo.
The lower photo above also shows the cam of the upper actuator that turns or clocks the gearshift command shaft through the hairpin duct. Here are some photos of the upper/smaller actuator.
Basically the seals and internals as they sit inside the Actuator housing is the same for the smaller and larger one. They just provide different functions as the hydraulic fluid is applied in the chamber itself. Please note in the photo below I took off the other brass type end cap. There are two just like the bigger actuator with seals.
Selection and Engagement
Selection: The gearshift command shaft has 4 possible positions separated by 15 degree angles it can rotate to. Again see the first of the photo way above of the four shift forks. Selection is the rotary movement up or down to the individual shift forks. The smaller hydraulic actuator converts the fluid pressure supplied by triggering the gear selection solenoids or valves into a rotary movement in order to move the gearshift finger to that end. The gear selection solenoids are EV3, EV4, and EV5.
Engagement: Once the rotation of the hydraulic finger has been obtained to the desired shift fork, the gearshift command shaft must then be push forward or backward to engage the gear for that fork. Again this is done through the stored pressure activated by the solenoids to the larger of the two actuators above.
The finger has three possible positions from this point: Even number gears and reverse gear/Neutral/Odd number gears. The engagement solenoids are EV1 for Odd number gears and EV2 for Even number gears (and reverse), both of them ON together for neutral.
Reading through this you would believe this is somehow accomplished slowly but it really isn’t. It happens very quickly, abruptly, and almost simultaneously. As a matter of fact, there is always at least 580 psi or 40 bar of hydraulic pressure in the system as it operates and goes as high as 725 psi or 50 bar at the beginning of the F1 pump being cycled.
Okay lets get into the brass tacks on how all of this works and functions with some pictures.
The photo above is the top part of the Actuator where the hydraulic pressure lines are banjo bolted to it.[ Small digression, on Ferrari, and Lamborghini these Actuators are positioned upside down from how you’d see it in a Maserati. Some are slightly different shaped. That’s unimportant to how it functions as an actuator as it’s all sealed and doesn’t matter how it’s positioned. ]
Let me get you oriented for the photo above, because I am going to tell you what each hole is used for.
The black “Selespeed” dust cover is usually covering on the right side of the photo. It looks like this when it’s on:
You can see the 6mm nut size on the smaller of the actuators hanging out there. The position of the Actuator as a whole above is exactly what it would look like sitting on the side GS/4200/Quat gear box, looking down on it from the top.
You have 5 chamber banjo bolt holes. Starting at the top going left to right, the three holes are:
- The EV#3 solenoid valve high pressure line hole
- The EV#4 solenoid valve high pressure line hole
- The EV#5 solenoid valve high pressure line hole
Left to right on the bottom is
- The EV#1 solenoid valve high pressure line hole
- The EV#2 solenoid valve high pressure line hole.
Here’s how it works in the vehicle:
- In order for Neutral to be selected and engaged:
- EV#1 #2#3#5 have to be on
- In order for 1st to be selected and engaged
- EV#1#3#5 have to be on
- In order for 2nd to be selected and engaged
- EV#2#3#5 have to be on
- In order for 3rd to be selected and engaged
- EV#1#3#4 #5 have to be on
- In order for 4th to be selected and engaged
- EV#2#3#4#5 have to be on
- In order for 5th to be selected and engaged
- EV#1#4#5 have to be on
- In order for 6th to be selected and engaged
- EV#2#4#5 have to be on
- Finally in order for Reverse to be selected and engaged
- EV#2 and #3 have to be on.
As it relates to the photo above the three top holes or EV3-5 banjo bolt holes go directly to the smaller actuator that selects/clocks (up and down movement) the gearshift command shaft actuator finger.
The two holes on the bottom go to the larger actuator that engages (or gives left to right movement) the gearshift command shaft.
Since the actuator I photographed was messed up I cannot show you how the top or smaller actuator moves out and in to clock the hair pin. I can show you how the lower one moves just as a general reference.
In the middle would be “N” you can see where the bottom actuator arm is sitting. Both EV#1 and 2 have to be on to achieve this.
This would be Even gears engaged or EV#2 on pushes the Engagement Actuator all the way to the right.
This is odd gears engaged, EV#1 solenoid is “on” to achieve all odd gears.
You might be wondering, what tells the NCR or the gear box ecu that the Hydraulic Actuator is actually in the gear it selected and engaged? After all just because you open the valves doesn’t necessarily mean the actuator finger will turn. It can and does at times malfunction correct?
The hydraulic actuator is equipped with two passive type sensors designed to monitor the actual position of the actuator finger. One sensor monitors the selection stroke while the other checks the engagement stroke. Both are hall effect sensors that convert the output signal of the hall ceramic element into a 0-5V DC signal. A failure of these sensors will disable the engine from starting. If the car’s NCR doesn’t receive the appropriate signal it disables the car as a safety feature. Alternatively, this is also the signal the NCR uses to show the driver the gear the vehicle is in through the indicator window on the dash.
Here are two photos showing those potentiometers when they are removed from the Actuator housing:
Here is where they sit:
If you look at how the potentiometers” armatures sit they look quite odd, but that’s for good cause and reason. If you look at the very bottom photo there’s a groove in the gearshift command shaft where both of the armature legs sit. When the gearshift command shaft is clock/rotated this pushes on the “shift” selection Potentiometer. When the gearshift command shaft is pushed left to right this operates on the “gear” engagement potentiometer.