3.09 4 Speed Gear Set Strength

Long ago I spent some time trying to get the most power possible thru the Saginaw 4spd.
Ratios available were...
2.54/1.81/1.44/1.00
2.84/2.01/1.35/1.00
3.11/2.20/1.47/1.00
3.50/2.16/1.45/1.00
3.50/2.47/1.65/1.00
The thing that might surprise some is that the actual 1st gear in all the above gearsets were all exactly the same, and interchangeable among all the different Saginaw 3 and 4 spd gearsets. The actual difference in the overall 1st gear ratios was in the front of the box, the input shaft and front cluster gear tooth count/ratio.

So at least in the case of my Saginaw example, the actual torque that gets applied to 1st/2nd/3rd gears depends on what ratio was at the front of the box. If you apply 500ftlbs to the input of the 2.54 gearset, 1st gear on the cluster would receive 660ftlbs. Apply that same 500ftlbs to the input of the 3.50 gearset, an identical 1st gear on the cluster would receive 906ftlbs.
...On the 3.50 gearsets, it was always the smaller input shaft gear that failed first.
...On the 2.54 gearsets, it was the small 1st gear end of the cluster that failed first.

Keep in mind that all those Saginaw gearsets use exactly the same 1st gear. If you were able to somehow "beef-up" the gears on the front of the 3.50 gearset to the point that 1st gear would then become the failure point for both gearsets, you would be able to send about 37% more torque to the 2.54 before reaching 1st gear's breaking point.

Even though all the gears themselves may be of equal strength, the ratio at the front of the box makes a difference in how much torque you can apply to the input shaft before reaching the failure point of 1st/2nd/3rd gears.

Grant