The internals consisted of parts mainly borrowed from the Rekord E1 and later the E2, which meant cloth seats, and much plastic on the dashboard and inner doors. Even the rev counter and the tachometer was taken directly from the Rekord E models, so that when you sat in one, the feeling was not that you drove a Monza, but more that you where driving a Rekord. If that wasn't enough trouble for Opel, they also experienced gearbox problems. The engine range for the Monza A1 was the 3.0S, the 2.8S, the newly developed 3.0E and later the 2.5E (the 3.0 had 180 bhp and 248 Nm with fuel injection), gave a wide range. The three-speed Borg Warner automatic transmission from the Commodore range needed to be modified to cope with the new and improved power outputs. Opel's own four-speed manual gearboxes were not up to the job and, instead of putting in a more modern five-speed manual gearbox, Opel turned to gearbox and transmission producer Getrag, and installed the Getrag 264 four-speed manual gearbox in the early Monzas. But when people bought a big, luxurious coupé they wanted modern products as well, and Opel obliged, as soon the Getrag 240 (for the 2.5 engines) and the Getrag 265 (for the 3.0E), both 5-speed manual gearboxes, replaced the old 4-speed gearbox.