When I said, "determine your shift points", I wasn't thinking of creating new internal transmission ratios. I should have said "see or visualize your shift points". The graph shows three slopes. The more vertical the slope the less time you have to do your shifting in the power band. At least this is how I see it. Hopefully someone will speak up if I'm in the ditch.
The graph can be used to help visualize, in a very rough way, the transmission you have now and the transmission you thinking about going to. Based on past conversations we have 3 speed, 3 speed O/D, 4 speed (SM420), 4 speed Hydramatic, conversions with 3 and 4 speed Saginaw transmissions, Tremec versions, T-5 and others. I've heard it said that you don't need a T5. A 4 speed Saginaw with a 3:11 first gear and a ?? rear axle ratio with ?? tire size will give you the same results.
To continue on, we figured out the cruising speed but what about launching this heavy metal truck to get it moving? As a general rule you want the launching gear ratio times the rear axle ratio to be around 9. A plain 3 speed with first gear of 2.85 times 2.70 (gas saving Camaro rear axle) = 7.7. You have to ride the clutch to get the truck to move. Ask me how I know. A 4 speed Saginaw with first gear of 3.50 times 4.11 (generic truck axle) = 14.4. Jack rabbit starts. A few dragstrip pulls then failure.
Looking back at 52Carl's setup. First gear is a granny so it is given that you launch in second gear of 2.37 (I am assuming this is the correct ratio for his transmission) times 4.64 = 11. That is on the stout side. He probably gives it light pedal to get it moving "pulling stumps down the road".
Last edited by buoymaker; 10/15/2022 9:47 PM.
