4 speed vs. 5 speed for stocker

[SSDiv6]

Any manual transmission, either 4-speed or 5-speed, needs proper gear ratio selection for optimum performance based on the power band of the engine. Engines with narrow power bands, benefit with 5-speeds.

The gear ratio selection needs to be optimized to allow the engine to recover and stay in its power band through all gears.

In order to keep their engines in the power band, I have known of SS racers with small CID engines, that must run a 4-speed, put a 1.1 or 1.2 high gear on their 4-speeds.

[Jim Caughlin]

The only way that I know to get a high gear of anything other than 1:1 would be to use a 5 speed as a 4 speed. All 4 and 5 speeds that are currently being used in Stock and SS 'lock' the main shaft in high gear and therefore have to be 1:1. Trust me, if there was an easy way to underdrive one of these, I would be doing it. I run a 4 cylinder in SS/FS with 6.50 gears and 28" tall tires and would love to have more RPM but that's all that is reasonably available. In the past, I have run 7.17's in a Dana 60 but they have a limited life. In the good old days of Doug Nash transmissions, there was a bolt on input underdrive unit available but nothing for our current transmissions. Not that I in any way miss my Doug Nash. The other drawback in my combination is the tiny input gear required for the low 1st gear ratios, the distance from the root of the tooth to the outside of the spline makes them capable of exploding, this leaves you with 5th gear only for a very fast trip back to the pits, probably exceded the 15 MPH speed limit...

Jim Caughlin
6019 SS/FS

[SSDiv6]

Originally Posted by Jim Caughlin

The only way that I know to get a high gear of anything other than 1:1 would be to use a 5 speed as a 4 speed. All 4 and 5 speeds that are currently being used in Stock and SS 'lock' the main shaft in high gear and therefore have to be 1:1. Trust me, if there was an easy way to underdrive one of these, I would be doing it. I run a 4 cylinder in SS/FS with 6.50 gears and 28" tall tires and would love to have more RPM but that's all that is reasonably available. In the past, I have run 7.17's in a Dana 60 but they have a limited life. In the good old days of Doug Nash transmissions, there was a bolt on input underdrive unit available but nothing for our current transmissions. Not that I in any way miss my Doug Nash. The other drawback in my combination is the tiny input gear required for the low 1st gear ratios, the distance from the root of the tooth to the outside of the spline makes them capable of exploding, this leaves you with 5th gear only for a very fast trip back to the pits, probably exceded the 15 MPH speed limit...

Jim Caughlin
6019 SS/FS

Yes, you are correct. The guys that have run a 1.1 or 1.2 have converted 5-speeds in to 4-speeds.