A/T - Overview and Performance Information: Overview
90bmw17 Group 24 Automatic TransmissionBulletin Number 24 01 90 (2111)
Woodcliff Lake, NJ October 1990 Service Engineering
SUBJECT: Overview of THM-R1 Transmission
MODEL: 525iA
Together with the introduction of the M50 four-valve engine in the E34, a new automatic transmission will be used for the first time. The transmission, designated THM-R1, is manufactured in Strasbourg, France by Hydra-Matic.
The THM-R1 is an electronically controlled four-speed automatic transmission with a lock-up clutch type converter. Two planetary gear sets, five multiple disc clutches, one sprag and one roller clutch, and a brake band are used to provide four forward speeds and reverse. Shift control is hydraulic, whereas shift pattern, shift quality, and lock-up clutch are controlled electronically through 5 solenoid valves.