The ZF 9HP is a nine-speed automatic transmission built by ZF Friedrichshafen AG subsidiary ZF Transmissions in Gray Court, South Carolina. It is a front-transverse transmission, used in front-wheel drive and all-wheel drive vehicles. ZF claims that it is able to save an average of 16% in fuel compared with current 6-speed automatic transmissions. The gear ratio spread is 9.81:1. The transmission has a torque range between 280 and 480 Nm. The 9HP is only 0.24 inches longer than, and weighs 16.5 lbs less than, the outgoing six-speed transmission. The compact packaging is achieved by using a number of innovative design features: a new compact hydraulic vane-type pump, two patented dog clutches, which replace bulkier conventional clutch packs, and a nested gear set. Land Rover and Jeep demonstrated the world's first nine-speed automatic transmissions for passenger cars at the 2013 Geneva Motor Show. The 2014 Jeep Cherokee featured the world's first nine-speed automatic transmission for a passenger vehicle to market. The transmission has been problematic, as customers of Jeep, Chrysler, and Acura models equipped with the transmission have experienced problems in their vehicles regarding slow shifting and noisy operation. ZF has said this is due to software problems, not mechanical issues.
How It Works
An Animated Drive Line Schematic & A Rotational Speeds Nomogram These ordinates are positioned on the abscissa in strict accordance with the proportions of the sun gears' teeth numbers relative to those of their rings. Consequently, the output ratios on the ordinate C4 follows closely to those of the actual transmission. Note that elements A and F are labelled interchanged.
9HP Nomogram
This interactive nomogram is a real geometric calculator exactly representing the rotational speeds of the transmission's 3x4 = 12 internal shafts for each of its 9 ratios, grouped according to their 5 permanent coupling on 4 joint ordinates and 3 independent ordinates. These ordinates are positioned on the abscissa in strict accordance with the proportions of the sun gears' teeth numbers relative to those of their rings. Consequently, the output ratios on the 6th ordinate follows closely those of the actual transmission. This advantageous geometric construction sets us free from famous and tedious formula, because all calculations are exclusively determined by lengths ratios, respectively teeth numbers on the abscissa for the 4 epicyclic ratios, and of rotational speeds on the 6th ordinate for the 10gear ratios. Legend:
Chrysler issued Technical Service Bulletins for the 2014 Jeep Cherokee to "fix rough and delayed gearshifts", and Acura has issued transmission-related recalls for the 2015 Acura TLX.
