We claim:
1. A counter shaft disconnect mechanism for truck transmission in lower gears, wherein the mechanism comprises a split counter-shaft assembly configured with an assembly of primary shaft and a hollow shaft, which can be selectively connected to each other for low-gear operation or disconnected from each other for highway-like running conditions.
2. Counter shaft disconnect mechanism as claimed in claim 1, wherein the split counter-shaft assembly comprises:

• a primary shaft;
• a hub fitted on the primary shaft adjacent the input shaft end thereof;
• a sleeve mounted on the hub;
• a hollow shaft mounted on the primary shaft for transferring radial loads acting thereon through roller bearings placed between the primary and hollow shafts, and a dog-clutch with a plurality of teeth is made on the common driven gear on the hollow shaft;
• a respective set of thrust washers and bearings fitted at each end of the hollow shaft for absorbing any axial load transferred between the primary and hollow shafts;
wherein the mechanism can be selectively toggled between a disconnect mode, in which, the power is transferred via input gear, hollow shaft, through the selected gear to the output shaft for highway-like running conditions; and a normal mode, in which, the power is transferred via the input gear and split counter shaft assembly to the output shaft in the conventional manner.
3. Counter shaft disconnect mechanism as claimed in claim 2, wherein a
selection switch is provided adjacent the driver’s seat for selecting the
transmission to be operated either in disconnect mode for highway-like running
conditions or in a normal mode to enable the driver to access the reverse gear
and first driven gear positions for starting and reverse gear operation.

4. Counter shaft disconnect mechanism as claimed in claim 1, wherein the primary shaft comprises a hub and sleeve arrangement for making its connection to the dog-clutch teeth made on fifth gear on the hollow shaft in the normal mode of the mechanism and for disconnecting the primary shaft from the dog-clutch teeth in disconnect mode of the mechanism.
5. Counter shaft disconnect mechanism as claimed in claim 1, wherein the primary shaft is made integral with first driven gear and reverse gear.
6. Counter shaft disconnect mechanism as claimed in claim 1, wherein the hollow shaft is made with the third gear and the drive gear of second gear either integral thereto or press-fitted thereon and the fourth, fifth and sixth gears are made integral to the hollow shaft.
7. Counter shaft disconnect mechanism as claimed in claim 2, wherein the hollow shaft is mounted on the primary shaft by placing a respective roller bearing at either end thereof and the remaining fourth, fifth and sixth gears integrally made on the hollow shaft.
8. Counter shaft disconnect mechanism as claimed in claim 4, wherein the mechanism facilitates the sleeve mounted on the hub to be disconnected from the dog-clutch teeth of the hollow shaft in the disconnect mode thereof, to transfer engine power via the input gear, hollow shaft, through the selected gear, to the output shaft for operating in highway-like running conditions.
9. Counter shaft disconnect mechanism as claimed in claim 4, wherein the mechanism facilitates the sleeve mounted on the hub to be engaged with the dog-clutch teeth of the hollow shaft in the normal mode thereof, to transfer engine power via input gear, hollow shaft, dog clutch and primary shaft of the split counter shaft assembly to the output shaft for the starting and reverse gear operation thereof.

10. A method of operating the counter shaft disconnect mechanism for truck
transmission in lower gears as claimed in claims 1 to 9, wherein the method comprises the steps of:
• Starting the truck with the counter shaft disconnect mechanism in the switched-off mode thereof;
• Shifting the transmission into first gear, second gear and then in third gear;
• Activating the disconnect mode operation of the mechanism on exceeding the threshold speed of about 30 kmph in 3rd gear;
• Shifting the transmission into 4th, 5th and 6th gears to continue running the truck at high-speed in highway-like conditions by disconnecting first driven gear, reverse gear and PTO from the output shaft;
• Downshifting by returning the truck to about 30 kmph speed and shifting the transmission in 3rd gear and deactivating the disconnect mode of the mechanism by truck driver; and
• Slowing down the truck and shifting the transmission into 2nd gear, then 1st gear for stopping the truck, whenever required.