Land Rover and Jeep demonstrated the world's first nine-speed automatic transmissions for passenger cars at the 2013 Geneva Motor Show.[2] The 2014 Jeep Cherokee featured the world's first nine-speed automatic transmission for a passenger vehicle to market.
Specifications
Basic Concept
The 9HP is only 0.24 inches (6 mm) longer than, and weighs 16.5 lbs (7.5 kg) 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,[3] which replace bulkier conventional clutch packs, and a nested gear set.[2] 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 207 lb⋅ft (280 N⋅m) and 354 lb⋅ft (480 N⋅m).[1]
^Layout • Input and output are on the same side • Planetary gearset 4 is on the input (turbine) side • Input shafts are, if actuated, S1, R1 + S3, and C3 (planetary gear carrier of gearset 1) + R4 • Output shaft is C4 (planetary gear carrier of gearset 4)
^ abStandard 50/50: 50/50 are above/below average step With consistently falling gear steps (row highlighted in yellow), the lower half of them (rounded down, here the first four) is always larger and the upper half of them (rounded up, here the last four) is always smaller than the average gear step (cell highlighted in yellow two rows above). Deviating gear steps (red bold) indicate an unfavorable gearset selection
^ abcStandard REV: reverse gear is similar to 1st gear Reverse and 1st gear should have the same ratio. Plus 11 % minus 10 % compared to 1st gear is good, plus 25 % minus 20 % is acceptable (red); even larger deviations (bold) can impair the driving experience, especially when towing a trailer. A torque converter can only partially compensate for this deficiency
^ abcStandard FIRST: gear step 1st to 2nd gear With consistently falling gear steps, the largest gear step is the one from the 1st to the 2nd gear, although it should be limited for a smooth gear shift. A ratio step of up to 5 : 3 (1.6667 : 1) is good, up to 7 : 4 (1.7500 : 1) is acceptable (red); above (bold) is unsatisfactory
^ abcdefStandard SECOND: 2nd degree steps above 1 With consistently rising (from right to left) gear steps, each 2nd degree step (first row highlighted in green) is larger than 1. Smaller than its predecessor is acceptable (red); smaller than 1 (bold) is unsatisfactory
^ abcdStandard SPEED: shaft speed difference increase One difference that runs counter to the consistent increase in shaft speed differences (second row highlighted in green) is acceptable (red); two consecutive ones (bold) indicate an unfavorable gearset selection
^C1, C2, and R3 share a common shaft S3 and S4 share a common shaft C3 and R4 share a common shaft
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 (carrier of planetary gearset 4) follows closely to those of the actual transmission. Note that elements A and F are labelled swapped (cf. legend below).
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 (+ reverse), 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 (carrier of the fourth planetary gearset) follows closely those of the actual transmission. This advantageous geometric construction sets us free from Willis' 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 10 gear ratios.
Legend
A: Dog brake (blocks S3 and S4) C: Brake (blocks S1) D: Brake (blocks R2) B: Clutch (couples S1 with input shaft) E: Clutch (couples C3 (carrier 3) and R4 with input shaft) F: Dog clutch (couples R1 and S2 with input shaft)
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.[7]
Chrysler issued Technical Service Bulletins (TSB) for the 2014 Jeep Cherokee to "fix rough and delayed gearshifts", and Acura has issued transmission-related recalls for the 2015 Acura TLX.[8][9]
Production
Production of the 9HP started in 2013 at ZF's Gray Court facility in Laurens, South Carolina. 400,000 units are produced per year.[10]
Production of the 9HP for Fiat and Chrysler vehicles began in May 2013 at Indiana Transmission Plant I (ITPI), followed by Tipton Transmission Plant in Tipton County, Indiana in May 2014.[11]