1960- explain the PRND21L shifter concept

[dmurphy44]

Seen this on a number of selectors but I have little understanding of what differentiates the D2, D1 and Low. I obviously understand Low, and I’m guessing that D2 uses all gears in the given transmission, but what’s with the D1? Saw it once on a ‘64 Fleetwood and have been unsuccessful in finding an answer online. The attached picture is of a ‘60 Bird.

Regards,
dmurphy44

 

[Ward 57]

If I remember correctly some manufactures even labeled D1 as 'S' for snow.It locked it into 2nd gear so there was less torque to the wheels so less likely of spinning the tires. 'L' locked it into 1st gear and D2 let it run through all the gears.
I don't know why the Fordomatic starts out in 2nd gear but these 'Y' blocks have so much torque it really doesn't matter. T-Birds were a personal luxury car so maybe less shifting was desired but 1st was available if wanted.

 

[74 Harley]

In my '61, D2 starts off in 2nd gear. D1 starts in first. L is low gear hold.

 

[dmurphy44]

If I remember correctly some manufactures even labeled D1 as 'S' for snow.It locked it into 2nd gear so there was less torque to the wheels so less likely of spinning the tires. 'L' locked it into 1st gear and D2 let it run through all the gears.
I don't know why the Fordomatic starts out in 2nd gear but these 'Y' blocks have so much torque it really doesn't matter. T-Birds were a personal luxury car so maybe less shifting was desired but 1st was available if wanted.

Thanks! Do you find one to be more ergonomical/practical than the other when driving?

 

[Ward 57]

Thanks! Do you find one to be more ergonomical/practical than the other when driving?

Just leave it in D2. The other options were for special circumstances. You have to remember the roads were not as good at that time and you needed options and they were available. Even my Colorado PU with auto trans allows me to pick the gear I want.

 

[doug7740]

Seen this on a number of selectors but I have little understanding of what differentiates the D2, D1 and Low. I obviously understand Low, and I’m guessing that D2 uses all gears in the given transmission, but what’s with the D1? Saw it once on a ‘64 Fleetwood and have been unsuccessful in finding an answer online. The attached picture is of a ‘60 Bird.

Regards,
dmurphy44

Cruise-O-Matic transmissions arrived in 1958. Cruise-O-Matic transmissions have a shift pattern of Low - D1 - D2. These transmissions start in Low in the D1 (Drive 1) position, but start in second in the D2 (Drive 2) position. The D2 position was there to allow starting in sand or snow in second gear to help prevent rear wheel slippage. D1 is the normal operation of the Cruise-O-Matic transmission. This allows the transmission to automatically shift from low to second to third. The Cruise-O-Matic had a 2.40-to-1 first gear ratio, 1.47-to-1 second gear and a 1.00-to-1 direct gear third.

Doug7740
1955 Thunderbird Blue