The ZF 4HP22 (part number 1043010699) is a 4-speed, longitudinal, torque-converter automatic transmission designed by ZF Friedrichshafen in Germany for rear-wheel-drive passenger vehicles. Controlled entirely via an internal hydraulic valve body rather than an electronic computer, it relies on mechanical linkages and governor pressure to dictate shift timing.

Core Internal Architecture

• Clutch Packs: Features five multi-plate friction clutch packs (labeled A through E).

• Brake Bands: Utilizes three brake bands to lock planetary gear elements.

• Overdrive Design: Built with a split-torque design where 4th gear bypasses the torque converter hydraulically for improved highway fuel efficiency.

Visual and Physical Layout

• Casing: Two-piece cast-aluminum housing consisting of a removable bellhousing and a main transmission case.

• Bellhousing: Specifically cast to bolt directly to the rear of the BMW M20 straight-six engine block.

• Identification Plate: A small metal data plate riveted to the lower side of the main housing, stamping the ZF serial number and the "1043 010 699" specification code.

• Selector Mechanism: Features a physical shift lever shaft on the side connecting directly to the cabin's floor-mounted PRND321 gear selector.

Application Details

• Vehicle Fitment: Standard factory equipment on the BMW E30 325i, 325is, and 325iX models.

• Power Rating: Rated to comfortably handle input torque of up to approximately 221 lb-ft (300 Nm).