ZF 9HP48: Overview and operating principle of a 9-speed transmission

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The well-known German manufacturer of automatic transmissions ZF Friedrichshafen AG launched production of new 9-speed automatic transmissions in mid-2013. The American Chrysler Group LLC also joined the production of these transmissions.

The ZF 9HP48 (948TE) is a 9-speed automatic transmission with electronic control. This transmission embodies the achievements of the latest technologies in the field of creating automatic transmissions for engines with transverse location on vehicles with both full and front wheel drive. As for the dimensions and characteristics of the 9-speed ZF automatic transmission, there are two modifications of this automatic transmission: the 9HP28 weighs 77 kg and is designed for engine torque up to 280 Nm, the 9HP48 model weighs 87 kg and is designed for an input torque of up to 480 Nm.

ZF 9HP48 sectional view
Sectional view
The stick diagram of ZF 9HP48
The stick diagram of ZF 9HP48

It's important to note that compared to the currently most common 6-speed automatic transmission for front-wheel drive vehicles with a transverse engine, the fuel economy of a car with a 9-speed automatic transmission reaches 16%, which is achieved primarily due to a higher total gear ratio of 9.84.

Features of automatic transmission ZF 9HP48 (948TE)

  • The transmission design eliminates the need for maintenance.
  • Transmission oil is filled for the entire service life.
  • The torque converter has a controlled slip function with electronically controlled locking in all gears.
  • The gearbox consists of: 4 planetary gear sets and 6 control elements.
  • The gearbox has a large overall gear ratio.
  • The control unit is adaptable and ensures high shifting quality throughout the transmission life.

ZF 9HP48 (948TE): gear ratios and specifications

ZF 9HP48 gearbox dimensions
ZF 9HP48 (948TE): Specifications
TypeAutomatic transmission OilZF Lifeguardfluid 9 / Mopar ZF 8 & 9
Number of gears9Oil volume7.2 liters
DriveFWD/AWDOil changeevery 60,000 km (≈ 37,000 miles)
Engine volumeup to 4.0 litersFilter replacementevery 60,000 km (≈ 37,000 miles)
Torqueup to 480 NmApproximate service life150,000 km (≈ 93,205 miles)
ZF 9HP48 (948TE): Gear ratios and gear steps
123456789R
Gear Ratios4.7132.8421.9091.38210.8080.699 0.5800.4793.805
Gear Steps-1.651.491.391.391.231.161.21.21-

The following table shows the clutches that are engaged to achieve the required gear ratios.

Solenoid apply chart

ZF 9HP48 (948TE) problems

  1. Refusal of automatic transmission in motion (the car does not go) — faulty control unit.
  2. Extraneous noise — shaft problems.
  3. Kicks, slipping. Mostly observed on a heated box — valve body problems.

    Other problems:

  4. There were problems with spontaneous shifting to neutral.
  5. Many cases with overhauls on runs up to 50,000 km.
  6. Rapid wear of dog clutch A.
Information about the problems of the ZF 9HP automatic transmission was taken from open sources.

ZF 9HP48 (948TE): Torque converter

The torque converter provides communication between the engine and the transmission. It is located in the torque converter housing. Power transmission from the engine crankshaft is performed hydraulically and mechanically via a torque converter to the gearbox. The torque converter is connected to the engine using a faceplate.

The torque converter has a hydraulically operated lock-up clutch, which is controlled by the control unit via an electromagnet in the valve block. The solenoid actuates the slide valves to regulate the hydraulic pressure to the clutch. This allows the control unit to operate in 3 modes of torque converter operation: unlocked, partially locked and fully locked.

Torque converters installed on gearboxes ZF 9HP48
  • 1 - turbine
  • 2 - impeller
  • 3 - stator
  • 4 - connection to the gearbox
  • 5 - one-way clutch
  • 6 - torque converter lock-up clutch
  • 7 - bolts for fastening the drive disk of the engine
  • 8 - torsion damper
  • 9 - the torque converter housing
  • A - torque converter installed on 2.0l GTDi and 2.2l TD4 engines
  • B - Torque converter mounted on Ingenium I4 2.0L diesel engine

Torque converter: One way clutch

One way clutch
1 - roller; 2 - housing; 3 - spring; 4 - inner ring;
A - Unlocked. B - Locked.

How it works: When the clutch is rotated clockwise, the rollers are sandwiched between the inner ring and the beveled surfaces of the clutch housing, forcing the inner ring to rotate, blocking clockwise stator rotation. When the clutch rotates clockwise, the rollers move away from the beveled surfaces and can rotate freely (without blocking) with the clutch housing, this allows the converter stator to rotate freely when the vehicle is braking.

ZF 9HP48 (948TE): Automatic Transmission Fluid Pump

The ATF pump is located in an intermediate plate inside the main gearbox housing. The intermediate plate is attached to the inside of the transmission main housing with studs and nuts behind the converter. The converter housing contains and drives a drive gear with an integral sprocket, which moves the drive roller chain to drive the ATF pump. Thus, the drive gear rotates at the engine speed.

The transmission fluid pump is a vane pump that can deliver pressure between 3.5 and 44.0 bar (50 and 638 psi). The pump can operate at speeds from 700 to 7800 rpm with a maximum speed of 8600 rpm.

Transmission pump installed on ZF 9HP48
  • 1 - ATF filter
  • 2 - intermediate plate
  • 3 - the leading gear wheel
  • 4 - stator shaft
  • 5 - drive chain
  • 6 - ATF pump

ZF 9HP48 (948TE): Dog clutches

The gearbox uses two dog clutches. Dog clutch A connects the input shaft to sun gear S2 and ring gear R1, and dog clutch F connects sun gears S3 and S4 to a centering plate installed in the gearbox housing.

Both dog clutches work in a similar way. Each clutch is controlled by ATF pressure acting on a double-acting piston to engage and disengage the dog clutch.

Dog clutch - A

Dog clutch A is located at the end of the input shaft and is controlled by a double-acting piston located inside the input shaft.

The double-acting piston is located inside the input shaft and can move inside the shaft when the ATF pressure is applied. The piston is connected to the dog clutch A by a pin that moves in the groove of the input shaft.

Dog clutch A of ZF 9HP48
  • 1 - planetary gear 1
  • 2 - measuring piston
  • 3 - Latch A
  • 4 - supply of ATF pressure for disengaging dog clutch A
  • 5 - input shaft
  • 6 - piston
  • 7 - planetary gear carrier
  • 8 - supply of ATF pressure for engaging dog clutch A

Latch A has two positions: "open" and "closed". The piston cannot determine if latch A is fully engaged or disengaged with the ring gear housing or remains in an intermediate position. Therefore, the piston is equipped with a measuring piston that allows the ATF pressure to be measured using a pressure sensor in the sensor block.

Dog clutch - F

Dog clutch F is located between multi-plate clutch E and planetary gear 4. Dog clutch F is controlled by a double-acting piston located in the bearing support housing.

Dog clutch F of ZF 9HP48
  • 1 - ATF supply - off
  • 2 - spur gear
  • 3 - a ring of an angular ball bearing
  • 4 - ATF supply - on
  • 5 - pressure measuring hole
  • 6 - sun gear 3 and 4
  • 7 - latch F
  • 8 - bearing support housing

Latch F is a sleeve with internal and external splines. The latch is constantly in engagement with the splines of the bearing support housing, which, in turn, is rigidly fixed in the gearbox housing. When the latch F is moved to the closed position, it acts as a brake for sun gears 3 and 4 in planetary gear 4.

How it works: If the ATF pressure acts on the right side of the piston, the piston is pushed to the left. During piston movement, a slight leakage of ATF pressure occurs through the measuring hole. This leakage pressure is measured from the left side of the piston by a pressure sensor in the sensor block. When the piston has moved fully to the left and reached its end position, leakage through the measuring hole is blocked. The differential pressure on the left side of the piston is recorded and the control unit can determine that dog clutch F is in full engagement with sun gears 3 and 4.

ZF 9HP48 (948TE): Transmission control module (TCM)

TCM is located at the top of the automatic transmission housing and is connected to the high speed CAN bus of the powertrain systems to communicate with other systems in the vehicle. TCM generates output signals to activate the transmission solenoid valves to control the transmission.

The engine control module (ECM) transmits engine control data over the powertrain high speed CAN bus. To effectively control the automatic transmission TCM requires engine data such as crankshaft torque, crankshaft speed, accelerator pedal angle, engine temperature, etc.

TCM processes signals from the transmission output speed sensor and from the temperature sensor, ECM and other vehicle systems. Based on the received signals and preprogrammed values, TCM calculates the required gear, torque converter clutch setting and optimum settings for controlling the shifting and locking clutch.

Transmission control module (TCM) of ZF 9HP

Towing a vehicle with ZF 9HP transmission

If the engine cannot operate while the vehicle is being towed, the steering and brake boosters will not work. This will require a lot of effort when steering or braking the vehicle.

The vehicle should not be towed further than is required to be loaded onto a trailer or tow truck. The recommended evacuation method is on a trailer or on a tow truck.

If evacuation on a trailer or tow truck is not possible (for example, a car off-road), the car can be towed with all 4 wheels on the ground for a distance of no more than 10 km (≈ 6 miles) at a speed of no more than 25 km/h (≈ 15 mph). Use the Parking Lock Service Release (SPR) procedure to deactivate the parking lock.

Useful information about the ZF 9HP: Service manual, research

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