Manual Transmission - AutoZone Refer to the manual transmission fluid recommendations for the proper viscosity of engine oil, or type of transmission fluid to be used for the T5R and NV1500 transmissions. Fill the transmission by pouring the new fluid through the fill plug hole in the side of the transmission. Fill until the fluid starts to dribble out of the filler hole. Isuzu Pickup Manual Transmission Fluid Change Cost The average cost for an Isuzu Pickup manual transmission fluid change is between $58 and $106. Labor costs are estimated between $26 and $34 while parts are priced between $32 and $72.