Torque Monster !
They can be shifted while moving. However you have to take your foot off the throttle, then shift, then get back into it. Not ideal, but I can plan ahead and shift before pulling a grade that may need it.
Yes but, from memory, the reduction is about the same as simply downshifting the main trans. About 33%; which turns a 5.56 into a 7.39, and rpm will jump from 2400 to 3200. Whereas a downshift from overdrive to "Drive "is 3480. I don't see a 2-speed particularly useful in this case.
But I do see it, if you do NOT have an overdrive trans, and worked the rear backwards like an overdrive.
Now for comparison, 4.56 x.69od in the A518, =3.15 for 70=2400
To equal that with a two-speed operating in reverse mode. would require
3.15 x1.33=4.20s in the back.
But say you found one with 3.91s.....
then, the planetary speed will be 3.91 x1.33=5.20 Now you could be in low range for take-off, hitting 4000 in drive at about 65mph, then into high range the Rs would drop to 4000 x 1/1.33=3000@ 65mph. Then into lock-up the Rs fall to 2550, still at 65; and 70 would then be 2750. Still in 3.91 Hi-range in the diff.
For comparison, 1/1.33= .75 or 75% That is a nice progression for the A727, which would be
2.45-1.45-1.00-.75"overdrive" ; with splits of
.59-.69-.75 just what your rig needs. I like it.
Looking at it in roadgears, with a 3.91 C&P starting out in 1.33 low-range, I get
12.74-7.54-5.20-3.91 and loc-up. And 70=2750
Compare that to the A518 and 4.56s;
11.17-6.61-4.56-3.15 and loc-up. And 70=2400
In "fourth gear" the 2-speed 3.91 is 24% better than A518.
With 400 ftlbs on tap, this amounts to
an extra 100 ftlbs available for climbing/etc without downshifting... which is a good thing, cuz those 2-speed units do not like to be downshifted at speed. Once you get to cruise-speed, you want to leave the two-speed in high range.
But as you can see, even with 3.91s your starter gear is 14% better for about a half-gear jump off the line.
In both cases, the TC will add it's own multiplier, varying perhaps from 1.8 to 1.1 ,with load and rpm.
I don't see a bad side to this idea.
You don't need an A518 nor adapters. Theoretically speaking, if you could find smaller than 3.91s for the back, you wouldn't need a loc-up either, But IDK if that is possible nor even desireable.
But then, you wouldn't need the 413 either, a stout 360........ like mine lol, would do the trick, you might just want to shift it a lil higher than 4000 and wait until 70 to hit Hi-Range.
Oh I can hear that Thermoquad-360 screaming thru the dual 3inchers already, lol.
360s can make 400 tq as well, they just can't give it to you from 2000 to 4000 rpm lol. But with a progressive shifting combo like the 2-speed delivers, it doesn't need to.
But hey, I know you got your sights set on the 413, and I can certainly see the attraction in cruising at 2400, with the engine sitting right there beside you. But to do that with a 2-speed would require a rear C&P of 3.36s, AND a loc-up besides.....if I am right about the 33% planetary ratio increase, going from memory, lol. (I used to build those for a living,back in the 80s)
More spitballing;
The more I think about this, Especially that short progressive shift out of Lo-range, the more I think how a Hi-pressure 360 could easily pull that with a a hi-stall/loc-up, and a short-period cam, and with only 4" pistons, and a long stroke(relatively speaking), Fuel Economy is a shoo-in. Ima thinking up to a 218/223 cam, alloy heads and 185/190psi minimum cranking cylinder pressure.
But hey, now the A518 bolts on....................
Are you thinking what I'm thinking?
Heck-ya. Run both the A518 AND the 2-speed.
Say Hello to 70= 2020 in od on the flat close to sealevel, but 2920 at altitude in Drive. And getaload of the take-off power in low range! with 4.10s now, your road gears could be
13.36-7.91-5.45-4.10-2.83, lo-range in red, hi-range in blue.
Count them; 5 speeds not including loc-up.
And nice progressive splits of .59-.69-.75-.69od
Yeah, no; the thermoquad on the 360, IDK if it can pull 70mph in 2.83rear gear, on the teensey primaries,lol. But if it did! now yur all set up, for mpgs.
BTW,
13.36 as above, with 33" tires is the same as;
10.73 with 26.5s, and 4.05s.,
With the TC adding it's multiplier and say a 2800 stall this would make a killer take-off in a 4000 pound car....... Yeah OK I get that your Travco will be a tad heavier than 4000, but you are not likely to ever floor your 413 from a standing stop either.
Ok now, suppose you did floor your 413, and it exploded into 4.56s at all 400 ftlbs. That maths out to 4469 ftlbs thru 2.45 first gear, into the rear axles.
But the 360 into 4.10s x1.33 will need only 335 ftlbs (84%) to match it.
Going back to the 100hp theoretical chassis requirement to cruise at 70mph. At 2020 the 360 would need 260 ftlbs to cruise on the flat. Your 413 at 2400 requires a lil less, at 219. But the 360 is not working all that much harder. And, taking it out of loc-up, might get you say 2376 rpm and now the requirement is 221 ftlbs...... lol.
I love this;
13.36-7.91-5.45-4.10-2.83, lo-range in red, hi-range in blue.
Count them; 5 speeds not including loc-up.
And nice progressive splits of .59-.69-.75-.69od
What do I mean without lock up?
Well the TC adds torque to every gear, depending on the torque going into it from the crank, and the resistance of the chassis to accelerating.
The ratio varies continuouslt between a possible hi of 1.8 to a possible low of 1.1. The multiplier is greatest at zero mph and least when cruising.
So then on the start-line, this 13.36 could be as high as 24:1 !! but as soon as the vehicle starts to move, this multiplier begins to diminish.
Lets say in first gear it averages 1.4, and let's say in second it averages 1.3 and in drive under load it averages 1.2, and when you put it into hi-range, 1.1
Ok your new ratios, which you will be seeing on the tach, reflect this
18.70-10.28-8.63-4.51/4.10locked-up, and 3.11/2.83locked up. Count them; I get 6 or 7,lol, ratios, depending on when you use loc-up. Good stuff.
Fun with math.
