ZF 4HP18 transmission

4HP 18 (FWD & RWD & 4x4)
4HP 18 (FWD & RWD & 4x4)
Overview
Manufacturer	ZF Friedrichshafen
Production	1987 – 1998
Model years	1987 – 1998
Body and chassis
Class	4-Speed transverse and Longitudinal Automatic Transmission
Chronology
Predecessor	ZF 3HP Transmission Family
Successor	ZF 5HP Transmission Family

The ZF 4HP18 is a four-speed automatic transmission for passenger cars from ZF Friedrichshafen AG for both longitudinal and transverse installation, identifiable by the suffix Q (german quer = transverse). Introduced in 1987, and produced through 1998, it was used in a variety of cars from Alfa Romeo, Audi, Citroën, Dodge, Eagle, Fiat, Lancia, Porsche and Saab.

Specifications

Gear Teeth and Ratios		Planetary Gearset Teeth^{[lower-alpha 1]} Ravigneaux		Count	Total	Avg.

Model	Version First Delivery	${S_{.1}}$ ^{[lower-alpha 2]} ${R_{.1}}$ ^{[lower-alpha 3]}	${S_{.2}}$ ^{[lower-alpha 4]} ${R_{.2}}$ ^{[lower-alpha 5]}	Brakes Clutches	Ratio Span	Gear Step
Gear	R		1	2	3	4
Step $i_{n-1}/i_{n}$	–R : 1			1 : 2	2 : 3	3 : 4

4HP 14	1987	34 29^{[lower-alpha 6]}	29 82	2 3	3.2647	1.4835
Ratio $i_{n}$	−2.8276 $-{\tfrac {82}{29}}$		2.4118 ${\tfrac {41}{17}}$	1.3688 ${\tfrac {861}{629}}$	1.0000 ${\tfrac {1}{1}}$	0.7387 ${\tfrac {82}{111}}$
Step	1.1724			1.7619	1.3688	1.3537

4HP 18	FLE 1991	38 34^{[lower-alpha 6]}	34 98	2 3	3.4737	1.5145
Ratio $i_{n}$	−2.8824 $-{\tfrac {49}{17}}$		2.5789 ${\tfrac {49}{19}}$	1.4067 ${\tfrac {294}{209}}$	1.0000 ${\tfrac {1}{1}}$	0.7424 ${\tfrac {49}{66}}$
Step	1.1176			1.8333	1.4067	1.3469

Ratio	$-{\tfrac {R_{.2}}{S_{.2}}}$		${\tfrac {R_{.1}R_{.2}}{S_{.1}S_{.2}}}$	${\tfrac {R_{.2}(S_{.1}+R_{.1})}{S_{.1}(S_{.2}+R_{.2})}}$	${\tfrac {1}{1}}$	${\tfrac {R_{.2}}{S_{.2}+R_{.2}}}$

↑ Planetary gearset orientation: output shaft is ring .2 (ring gear of outer Ravigneaux gearset part)
↑ Sun .1: sun gear of inner Ravigneaux gearset part
↑ Ring .1: ring gear of inner Ravigneaux gearset part
↑ Sun .2: sun gear of outer Ravigneaux gearset part
↑ Ring .2: ring gear of outer Ravigneaux gearset part
1 2 inner and outer sun gears of the Ravigneaux planetary gearset are inverted

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