IMO
on the street; as in a city-car;
I have had the most fun with cars that were geared correctly for what I have wanted to do, and had the governor pressure cranked up, and then I can shift the trans with the gas pedal. And with adequate governor pressure, the trans will downshift 2-1 very willingly. This leaves my hands free to concentrate on steering.
On the street, you are limited to using mostly Second gear, occasionally First.
At any particular rpm, your engine is wanting a particular gear ratio, and it doesn't care how you get it. It can be a deep rear and a hi trans gear or vice versa. For example; with a 2.66 low and 3.73s the overall ratio is 9.92. But you can just as easily get about that, with a 3.09 low and 3.23s. The engine does not care how you get that ratio at a particular rpm.
And the rpm to gear, ratio, is linear, so if you are at 2000 rpm with that 9.98 ratio, then your speed will be ~16mph.... so at 4000rpm, your speed will be ~32mph, and at 6000 it will be ~48mph.
With a 318/904, I like to be in the fat part of the torque curve, in Second gear, at about 30/35 mph. This will produce an almost flat power delivery with no peakiness. The stock cam makes peak torque VERY early, say 2800rpm. So with a 1.45 second gear, I need a 4.10 rear, for 2800=32mph at 15% slip. This in theory, would allow me to run to 64mph at 5600, but the slip will be down to say 10% so 5260rpm, which is a stretch for a stock-cammed 318. So I put some valve springs on it just to be sure it goes there.
In reality, with that 318, I run a 4.30, cuz that just really wakes her up. And I run a 2800TC. And I run the A999ratios, lol. And a 4bbl with headers and dual 3inch sewer pipes all the way. So I cannot hit 64 mph in Second, which is no big deal; I can still hit 60@5500, but as you can imagine, the smoggerteen quit pulling a long time ago,lol. But with 4.30s it winds up pretty quick, so it's hard to notice .....
The power of the smoggerteen also comes in quite early, perhaps 4200. Which with 4.30s is about 48 mph. And the shift rpm might be 4500rpm/51mph. So my powerband in Second gear, is from 32mph to ~50 mph. I want the trans to stay in Second gear. I won't be up-shifting it. And I don't want the governor to throw a surprise downshift at me either.
These are all things to think about when you plan your application.
Now; 1.54 x 4.30=6.62 ratio. That will be my ratio of choice. With a 904, you can do this in 2.45 first gear; with a rear gear of 6.62/2.45=2.70, rounds to 2.76s..... but taking off in 6.62ratio, with a low-compression 318, and a stock stall .....is a tad um sluggish; even with a 2800. And the big surprise comes when you shift into second and that .59 split hits you. Outshifting first at 4500/48 mph, the Rs will drop to 2660, and there you are, gasping and wheezing, until the engine gets back up on the cam. The A999 ratios make it even worse, dropping to 2530. Lord help you if the vacuum secondaries slam shut.
But the 2-3 split in the 904, is .69, so the rpm only drops to 4500 x.69=3100. It is for this reason that I run the 4.30s. In the A999 the 2-3 split is a reasonable split of.65, so the Rs drop to 2920; still a long way from 2530.
So the cure for that sluggishness is more cylinder pressure and/or a higher stall, or some combination of those two; and a mechanical-secondary carb. Or, if you just can't see running 4.30s or 2.76s; then run a very hi-stall, or a bigger engine. I have run a hi-compression 340 fully dressed as a 318 including the cam, and it was a blast for sure. I ran it with a 904. And altho I never checked, I suspect the rear gear was no bigger than 3.23s; probably less.
But for the guy who just likes or needs to point and shoot, I guess a full manual-shift automatic might be all right............. for the ONE WOT upshift (on the street) you might be doing in the zero-to 60 time-trial. But for me, if I gotta shift it like a manual, ALL the time; then I'm getting an actual manual trans with the extra gear(s), and an actual clutch that is able to act like a "variable stall".
But I'm more of an autocross kind of guy. I like slammin' it around, slipping, sliding, drifting, with a generous amount of full lock stuff, and 360s; including accidental ones to make it interesting.
Who's got time to manually shift it?
I just stick it in second, set the rev-limiter to 60 mph, and let her buck. And I've got the traffic tickets to prove it..... lol. NO speeding tickets in this car ever.
These are my experiences interlaced with a bit of opinion, and the opinion parts is/are clearly stated as they occur.
