A transmission system for vehicles, said transmission system comprising: a first set of plurality of input shafts and a second set of plurality of input shafts operatively connected to different power sources, said plurality of input shafts being concentrically disposed one within the other with the inner shafts extending with respect to the outer shafts to expose at least a portion of each of said input shafts, wherein the first set of plurality of input shafts and the second set of plurality of input shafts are disposed in a spaced-apart substantially parallel configuration; a first clutch means configured to connect the first set of plurality of input shafts to one of the power sources and a second clutch means configured to connect the second set of plurality of input shafts to a different one of the power sources, wherein each input shaft from the first set of plurality of input shafts is operatively connected to a clutch in the first clutch means, and wherein each input shaft from the second set of plurality of input shafts is operatively connected to a clutch in the second clutch means; one output shaft provided in operative communication with said input shafts (110, 116) for conveying a power output from the transmission to at least one set of wheels, wherein said output shaft is positioned substantially parallel between the first set of plurality of input shafts and the second set of plurality of input shafts; a plurality of input gears (102, 104) arranged in spaced parallel disposition on the exposed portion of each of said input shafts (110, 116), each of said input gears (102, 104) having a different pitch diameter for constituting the transmission gear ratios; dog clutch means (124, 126) disposed on the exposed portion of each of said input shafts (110, 116) and configured for locking selectively each of said input shafts (110, 116) to its respective input gears; and plurality of drive gears arranged in spaced parallel disposition on said output shaft for operatively engaging in drive relation with said input gears (102, 104), said drive gears being configured to transmit power to said output shaft from said input shafts (110, 116) by means of said input gears (102, 104); an additional clutch means provided at one end of the output shaft for selectively engaging and disengaging the transmission system with a set of wheels; wherein, when power is transmitted through any of said plurality of input shafts (110, 116) to its respective input gear, said dog clutch means (124, 126) are adapted to lock at least two input shafts with its respective input gears thereby preparing said transmission for a consecutive gear shift. a first set of plurality of input shafts and a second set of plurality of input shafts operatively connected to different power sources, said plurality of input shafts being concentrically disposed one within the other with the inner shafts extending with respect to the outer shafts to expose at least a portion of each of said input shafts, wherein the first set of plurality of input shafts and the second set of plurality of input shafts are disposed in a spaced-apart substantially parallel configuration; a first clutch means configured to connect the first set of plurality of input shafts to one of the power sources and a second clutch means configured to connect the second set of plurality of input shafts to a different one of the power sources, wherein each input shaft from the first set of plurality of input shafts is operatively connected to a clutch in the first clutch means, and wherein each input shaft from the second set of plurality of input shafts is operatively connected to a clutch in the second clutch means; one output shaft provided in operative communication with said input shafts (110, 116) for conveying a power output from the transmission to at least one set of wheels, wherein said output shaft is positioned substantially parallel between the first set of plurality of input shafts and the second set of plurality of input shafts; a plurality of input gears (102, 104) arranged in spaced parallel disposition on the exposed portion of each of said input shafts (110, 116), each of said input gears (102, 104) having a different pitch diameter for constituting the transmission gear ratios; dog clutch means (124, 126) disposed on the exposed portion of each of said input shafts (110, 116) and configured for locking selectively each of said input shafts (110, 116) to its respective input gears; and plurality of drive gears arranged in spaced parallel disposition on said output shaft for operatively engaging in drive relation with said input gears (102, 104), said drive gears being configured to transmit power to said output shaft from said input shafts (110, 116) by means of said input gears (102, 104); an additional clutch means provided at one end of the output shaft for selectively engaging and disengaging the transmission system with a set of wheels; wherein, when power is transmitted through any of said plurality of input shafts (110, 116) to its respective input gear, said dog clutch means (124, 126) are adapted to lock at least two input shafts with its respective input gears thereby preparing said transmission for a consecutive gear shift.