According to my service manual: 3 speed Dearborn was used as the standard transmission for full size Pontiac and as heavy duty transmission on Tempest and Firebird. Fully synchronized. Gear ratio 1st...2.42:1, 2nd...1.61:1, 3rd....1.00:1.
3 speed Saginaw was the standard transmission on Tempest and Firebird (except 400ci V8 engine). (Not synchronized). Gear ratio 6 cyl 1st....2.85:1, 2nd....1.68:1, 3rd....3.00:1 V8 (all but 400) 1st....2.54:1, 2nd....1.50:1, 3rd....1.00:1
4 speed Saginaw was used on ALL 4 speed Tempest and Firebird 6 cyl. engines. Fully synchronizes. Gear ratio (Firebirds) 1st....3.11:1, 2nd....2.20:1, 3rd....1.47:1, 4th 1.00:1. (Tempest ratios slightly lower.
4 speed Muncie is used with all v8 engines in full size Pontiacs, Tempests and Firebirds. Fully synchronized. Both Std and close ratios available. Gear ratios (std) 1st....2.52:1, 2nd....1.88:1, 3rd....1.46:1, 4th....1.00:1. (close ratio) 1st....2.20:1, 2nd....1.64:1, 3rd....1.28:1, 4th....1.00:1.
With this said, it is the low 1st gear on my Saginaw 4 speed that is realy too low (3.11:1 compared to the Muncie 2.52:1, or 2.20:1) I can really get off the line fast, but there is a huge gap going into 2nd gear.
