Ordered a gear vendor, help with deciding gears
That’s what it’s about for me. Sure, I’d like to not have to do floor mods, but if I need to for the result I want to fit with what I’ve got, I’ll do it.
IMO
a 4-speed automatic with a hi-stall and loc-up. is a better idea than a GVod behind a Mopar automatic.
Yur 4-speed auto will act like a 5.5 speed.
You wanna see how?
Ok I'll give you the short version;
The Hi-stall will give you an extra bottom gear, and the loc-up will give you a half a gear for cruising, so 4 +1 +.5=5.5
But IMO, the A500 has ratios that are way too far apart, and the A518 are still too far apart.
All the gears are in the same case, so you don't have to deal with the add-on GVod. And you can never bust the GVod by backing up with it still engaged..... Like I did. If I was not a stick-man, I would open up the tunnel in a heart beat.
The A500 has a starter of 2.74 and finishes at .69 for a range of 2.74/.69=3.97, which,IMO, is too broad, and individually, the gears are a lil too far apart for performance, for a small block, but not for a stroker.
The A518 is 2.45/.69=3.55 still too far apart for a 4 speed. But the Chevy's are not much better, most are actually worse. But they are more compact and fit better in the tunnel with less mods.
Page 2
Suppose you were geared for 65=2200, which will take 3.91s with a .69od.
Lets look at what the math says; your road gears are (trans times diff)
9.58-5.67-3.91-2.70 But is that what your engine sees?
no
the convertor is in between them, adding it's ratio that varies continuously with torque input and roadspeed. At zero mph the ratio may be as high as 1.8 and at 100mph it might be as low as 1.1.. Thru each gear the ratio will vary with torque input so we will have to average the TM(Torque Multiplication) by guesswork.
Let's use
1.6 on the start line; then
1.4 thru the rest of first, then
1.3 in second gear and
1.2 in third. then
1.1 in overdrive, then
1.0 in od/locked up.
So your new ratios are ;
say average of 15.33/13.41-7.37-4.69-3.24-2.70
Count them; I see 6, but lock up is only worth 200 to 250 or so.
So I call it a 5.5
as to splits I see;
.87-.55-.64-.69-.83
So lets say you have a shift-rpm of 5500. Then on each shift, your rpm will fall to those percents. On the 1-2 to 3025, on the 2-3 to 3520,on the 3-4 to 3795, and into locup at 65 , from 2425 to 2200, or 225rpm in this case.
Of course this assumes a stall of 3025 or less.
So now
Because the 5500 shift dictates a power peak of about 5200, your powerband has to be from 3025 to 5200=2175; that's pretty big , but you can get away with smaller on the 1-2 so going by the third gear, the powerband could be as small as 5200 less 3520=1680; there yago.
But just to remind you; 5500 at the top of 1.45-second gear with 3.91s is 64 mph, so as a streeter, what do the numbers really mean?
Answer; IMO, not much. Go ahead, determine your zero to 60 times with any two rear gears you want. If the tires spin all thru first, I doubt the results will be meaningful. If you have to peddle it to get traction, yurdone.
But that does not negate cruising at 2200 in .69od versus 3200 both with 3.91s. And even if 3.91 are not quicker to 65 in real time; it will certainly feel quicker. Fix the tirespin and then it will be quicker.
My 2cents
Now you just gotta figure out how to satisfy her need for cruise-timing at 2200 rpm.
