Thanks Deuce Coupe. That is some interesting info. In the late 70s I think there was a school of thought at GM that said use a deep first gear, would work the same for performance with a higher rear gear .the 700r4 is an example. Another example would be Lifeguards Camaro with a 3.50 first gear three speed.i am still tossing around a trans swap. The 200 is the easy fit, next would be a 200r4. A 700r 4 would be more work but might be worth it. For about $500 a 3.06 first can be had for the th350 but the jump to second would still be 1.52. I have a 2.73 rear axle so the OD won't help much even with a low rpm cam that I plan to run. If I had a power glide car a th350 or th200 or a 200r4. Would one of the first things I would do. The first two are almost a bolt in for some cars, not sure about an early nova. Looking at your nova, the 60' gain is huge. Driving on the street would be mor fun too. Some time ago, you ran my car through the famous Gonkulator and said the gain for going to a 2.74 first from 2.52 wouldn't be worth it. Jay
Yeah, I think you were on to something when you recommended the 4spd for my application instead of the 3spd, when I mentioned how hard it is to find a good speed from a stoplight to go from 1st to 2nd. With my 3.50:1 first gear (2.73 "perf" ratio in open carrier), the jump from that to 1.89 in 2nd is pretty steep. Breaking that shifting up into 2.47 and 1.65 would ease the transition. Or just going to a 3.11:1 1st gear 3spd (or 4spd might be better than a 3spd). When you get to the standard 2.85:1 3spd of pre-'75, there seems little point in shift twice rather than once before direct drive. The deeper first allowed a higher rear end ratio, which is a stop-gap fix on their way to overdrive transmissions. The Gonkulator gave me a 0.2 second 1/4 mile improvement from changing 3.5-3spd to a 3.5-4spd. But there was no improvement for the 3.11-4spd (maybe I should have had him run the 3.11-3spd too?). And changing to a 3.08 rear would be marginal improvement. Here, this is probably simpler:
3.5-3spd/2.73 = 3.5-4spd/2.56 = 3.11-4spd/2.73 < 3.5-4spd/2.73 = 3.5-4spd/3.08 = 3.11-4spd/3.08
The deeper the first gear, the more gears you need in-between to smooth transition. That's why a deep 3.06 1st in a TH350 was probably never attempted. But once you have OD, you don't need a real deep first. With the 4 gears on a 700 or 200, the 200's first gear makes more sense with a deeper rear end gear being the advantage of the OD 4th.
I looked at how GM changed 1st gear and rear end ratios over the years and the pattern I saw was:
2.85/3spd - 3.08/std - 3.42/perf - (3.73/hi-perf?)
3.11/3spd - 2.73/sted - 3.08/perf - (3.42/hi-perf?)
3.50/3spd - 2.56/std - 2.73/perf - (3.08/hi-perf?)
The TH350 kept getting the lower gear as the 3spd without changing the 1st gear. So it had a 3:08 pre '76, then a 2.73 pre '79, and finally ending up with the 2.56. So sounds like from the Gonkulator a TH350 with 2.73 is ok, but if going to a 200, then a 3:08 rear should be used?
