Transmission for vehicle

A transmission for a vehicle, comprising:

• a first input shaft continuously receiving rotational power from a power source;
• a second input shaft selectively receiving the rotational power of the power source through a clutch;
• a first counter shaft and a second counter shaft connected to the first input shaft and the second input shaft through transfer gear pairs, respectively;
• a controlling device selecting the transfer gear pairs to transfer the rotational power from the first input shaft to the first counter shaft or to transfer the rotational power from the second input shaft to the second counter shaft;
• a one-way clutch allowing the rotational power provided to the first input shaft to be transferred only from the first input shaft toward the first counter shaft;
• and
• a shifting device part including a plurality of shifting gear pairs provided on the first counter shaft, the second counter shaft, and an output shaft thereamong, selecting a shifting gear pair appropriate for a driving speed by one of synchronous devices, and transmitting the power provided from the power source to the output shaft,
• wherein the shifting gear pairs include:
• a plurality of sub-shifting gear pairs provided on the first counter shaft and the output shaft to have different gear ratios;
• and
• a plurality of main-shifting gear pairs provided on the second counter shaft and the output shaft to have different gear ratios,
• the shifting gear pairs are configured so that same gear ratios are present between total gear ratios from the first input shaft to the output shaft through the sub-shifting gear pairs and total gear ratios from the second input shaft to the output shaft through the main-shifting gear pairs, and
• the synchronous devices include:
• a 1 and 4-stage sub-shifting synchronous device selecting a 1-stage sub-shifting gear pair or a 4-stage sub-shifting gear pair;
• a 2 and 3-stage sub-shifting synchronous device selecting a 2-stage sub-shifting gear pair or a 3-stage sub-shifting gear pair;
• a 1 and R-stage main-shifting synchronous device selecting a 1-stage main-shifting gear pair or an R-stage main-shifting gear pair;
• a 2 and 3-stage main-shifting synchronous device selecting a 2-stage main-shifting gear pair or a 3-stage main-shifting gear pair;
• and
• a 4 and 5-stage main-shifting synchronous device selecting a 4-stage main-shifting gear pair or a 5-stage main-shifting gear pair.