The following will be the engineering process to design and build the transmission internals including input and output shafts, gears, and shifter mechanism to include 7 forward gears and one reverse in my project Subaru Justy.
Design Specifications:
1) Seven Forward gears
2) Granny low gear.
3)Taller than stock first gear.
4)Low rpm cruising sixth gear.
5) Lower than stock reverse Gear.
6) Sequential Gear Selection.
7) 300 ft-lb capability.
8) Fit into original transmission casting with minimal modifications.
Current Configuration:
Five forward gears
"H" pattern shifter
Current Ratios in Justy.
Research:
Desired gear ratios for all eight gears including final drive calculations.
Desired gear tooth option for each gear.
The following will be a comparison of the desired gear ratio versus the stock gearing with relative speeds. Assumed maximum engine rpm is 6000 rpm plus or minus 500 rpm.
Blue band being desired gear ratio and green band being current configuration.
Low gear would have a usable rpm range from below 2 up to 7+ mph
First gear will be taller with a usable speed range from about 8 mph up past 35 mph.
Second gear will be usable from below 15 mph up to 55 mph
Third Gear will be usable from about 15 mph to 70+ mph.
Fourth gear will be usable from below 25 mph up to 95 mph.
Fifth Gear will be usable from 30 mph up past 125 mph.
Sixth Gear will be usable from 45 mph up to over 140 mph.
Reverse will be lower than stock and have a speed range from around 4 mph up to 15 mph.
Component Design:
Input Shaft
Output Shaft
Low Gear
Input
Output
First Gear
Input
Output
Second Gear
Input
Output
Third Gear
Input
Output
Fourth Gear
Input
Output
Fifth Gear
Input
Output
Sixth Gear
Input
Output
Reverse Gear.
Input
Output
Component Testing with FEA: