A modular transmission for an electric drive system that includes multiple individual drive modules configured to each provide two forward and two reverse gear ratios. The individual drive modules optionally include separate and distinct housings at least partially enclosing a planetary gearset. A shifting assembly is optionally included for each drive module that is operable to selectively couple the ring gear either to the carrier, the sun gear, or to ground to achieve two different gear ratios. Multiple drive modules may be coupled together using corresponding mount points of the housings thus allowing a transmission and drive system to be formulated quickly, or to be modified or repaired, without undue time and expense. An electric motor may be arranged upstream, or downstream of the multiple individual drive modules, or positioned between modules.

A hybrid electric gas turbine engine two speed transmission for a low spool drive including an accessory gearbox in operative communication with a low speed spool motor-generator; a transmission in operative communication with the accessory gearbox and the low speed spool motor-generator; a low speed spool angled gearbox in operative communication with the transmission; and a low speed spool in operative communication with the low speed spool angled gearbox.

In a transmission of the present invention, a transmission case has a peripheral wall with an opening sized to allow an HST to be other than a main plate of the HST. The HST has the main plate and a sub-plate sandwiching members out of a center section, a pump-side holder and a motor-side holder that face to each other with the pump main body and the motor main body being arranged between the members. The sub-plate has an engaging portion, and the transmission case has a mounting seat with which the engaging portion is engaged in a slidable manner so that the HST is guided until an installation position.

A gearbox includes a housing, input shaft, and a geartrain. An input gear fixed to the input shaft is rotatable about an input axis. An idler gear is rotatable about an idler gear axis and supported by a mount. Output gear(s) are rotated from the idler gear. The mount includes a mount pin extending along a mount axis through the idler gear and an opening in the housing, and an eccentric bushing positioned around the mount pin and centrally within the idler gear. The eccentric bushing is rotatable about the mount axis to alter an offset between the input axis and the idler gear axis. A fastener can lock a position of the bushing in relation to the housing. The fastener is engageable in a first/second hole of the housing to accommodate a first/second gear ratio between the input gear and the output gear(s).

A hybrid electric gas turbine engine two speed transmission for a low spool drive including an accessory gearbox in operative communication with a low speed spool motor-generator; a transmission in operative communication with the accessory gearbox and the low speed spool motor-generator; a low speed spool angled gearbox in operative communication with the transmission; and a low speed spool in operative communication with the low speed spool angled gearbox.