From those with experience, any input good or bad is appreciated.
It's not a bolt-in, but as far as HotRodding goes, it's a cakewalk.
Previous posts here are correct. Except:
In my 68 Barracuda, even after clearancing, the unit hung a tad low to install the Crossmember. (my engine has been slightly raised for header fit.) So I got me one from a 73-up with a poly mount, and slotted the holes until the mount was as low as it would go, then slotted the holes in the crossmember just a lil. Because the GV is hung on the back and sticks back roughly 20/23 inches (guessing), this dropped the back of the unit, and changed the driveline angle, which, because my car is lowered a few inches, caused a modest vibration that took me a few weeks to minimize. But I never really got rid of it 100%. Not to worry, in my combo 65=2240, so at hiway speed it's as good as unnoticeable, and, in any case, is less than the stinking sticking CenterForce flyweights.
Ok so that got it installed.
Now, my 3" TTI H-pipe wouldn't fit, so I had to deal with that. I cut it out, and immediately my little 367 lost low-rpm torque, so I had to deal with that. My solution ended with installing the Commando 3.09 low gear set.
Now I had to deal with my 3"sewer pipe cooking the shift solenoid. I fabricated a shield.
Finally came the electrics. Mine came with effing huge switch that looked like it belonged in a hiway tractor. But I dutifully installed it and off I went for a roadtest. Holycrap, I said to myself, this thing shifts soooooo slow; there's no way that's gonna work for splitting!
So I rigged up a computer bypass for testing purposes..... and holycrap I said to myself, this thing shifts like lightning!
So out came the computer and out came that graintruck shifter. And in went a micro switch, a relay, and a dash-lite indicator to tell me when it was engaged. And I got used to softening the hit with a lil toe on the clutch.
Now, all that remained was to finalize the rear gear choice.
I had about every gear from 2.76 to 4.30s except not 3.73s. and a few others besides. Already installed were the 3.55s, and with the Commando 3.09low, this was very nice. I tries a few others but kept coming back to the 3.55s, and eventually that's were it stayed.
Here's why: My new ratios were;
3.09-1.92-1.40-1.00-.78od in Roadgears with 3.55s; this is;
10.97-6.82-4.97-3.55-2.77 This is a range of 10.97/2.77=3.96 or about 400%. Furthermore, the splits are;
62%-73%-71%-78% But I hit the od after third so my splits are;
62-73-78-71 into Final-Drive
IMO there is almost no finer spread amongst any of the commonly available aftermarket transmissions. 400% is just right.
Furthermore, when I split-shift, I split the 1-2 and, again after Second, then hit 4od like this
3.09-2.41-1.92-1.50-.78od the splits are
.78-.80-.78.-52
1.50 ratio gets me 93mph@6170
My power peak is at around 5200, and I shift at anywhere between 5500 and 7000. At 5500 the .78split drops the Rs to 4290, which is a powerband of 1210; need I say more? the little 367 is a rocket turning 93, in the Eighth.
But hang on, it gets better;
with 3.55s I can hit 60@5100 in Second, or 6400 in First over.
But it gets even better; With the Commando, and my 230* cam, I can hit 4mph@550rpm, or 3.66@500rpm.
And these are the reasons I run 3.55s
Now, as to would I do it again? the answer is probably not. The GV is not without faults: such as
1) The biggest is that if you accidentally leave the unit engaged in reverse, you will instantly break it. And you cannot buy the tools to take it apart yourself, and it will cost you 60% of retail plus shipping both ways, to get it fixed. So I suggest that you install the shifter with a ground-interupt relay off the back-up lights.
2) you cannot down-shift with the unit engaged, see above.
3) shifting at full power with stock-type clutch-discs, will destroy clutch hubs, or shred the discs. I have accumulated a pile of them. So I have learned to toe the clutch at the shift
4) the unit does not shift instantly; there is a tiny lag, which you have to learn to anticipate, and it seems to change with driveshaft rpm.
5) The unit will not hold pressure thru a stoplite, and the car will have to move ahead for one to two carlengths, depending on your reargear, to build enough pressure to re-engage, all the while, slipping. I found this out, with the 4.30s, trying to start out in First-over which is a roadgear of 10.36, which ratio, IMO, is about ideal for my combo.
On a different note;
If yur running a cam, with more than about 50* of overlap(@.008tappet), then there is a very real possibility of trying to run a cruise rpm that is too low for optimum fuel economy. Too low and the intake charge gets messed up and headers will pull A/F charge right across the pistons and out the back door it goes. 2200 is about the lower limit. The more overlap your cam has, the higher the limit gets. Also, below ~2400rpm it becomes extremely difficult to give the engine the ignition timing it craves. My engine at a Dcr of ~8.8, and pressure if ~180psi, likes 60 degrees@65=2240. But I can only give her 56* with the current set-up. It is what it is.
So, if there was ever a next project for me, I would spring for a proper 5 speed, with a similar 400% gain.
Actually; I'd probably switch to a 4-speed auto, with a modest stall, a lock up, and an SBM with a more modest than 230*cam, but with more than 180psi cylinder pressure ......... lol. Such a combo will perform like a 5.5 speed having a 2-speed convertor and a half a gear in the LU.
Now, I think it's worth saying that with a Commando 4-speed and a high pressure 360, honestly; if your cruise speed is limited to 65, you could easily build a clutched engine to work very well with 3.23s for 65=2600, or with 2.94s for 75=2700
I myself ran many years with 3.55s, @55=2650 with short tires.
These are easy rpms for which to supply max cruise-timing.
The Commando has a 16% lower first gear, so it's possible to take that same 16% out of the back, which means that 3.23s start like 3.73s, or 2.94s like 3.41s.
Here is a Roadgear comparison of a 70 Swinger340 that came with the T/A box and 3.55s, to the Commando with 3.23s/2.94s
8.77-6.28-4.76-3.55 (The T/A)
9.98-6.20-4.52-3.23 (the 2.66 box would have a 8.59 starter)
9.08-5.64-4.12-2.94, (the 2.66 is a 7.82 starter)
11.52-6.23-3.73-2.72 (The A833od with 3.73s)
From 6.28 to 5.64 (the Second gears) is a loss of 10%, but a 360 easily makes that up, in that it is 6% bigger, and makes inherently more torque. I have run 2.94s behind my 367/Commando, and can attest that, it was no slouch, in the bottom two gears.
This Commando/2.94 combo, is, IMO, a far better combo than the A833od with say 3.73s, see chart.
With a 360 I'd recommend a starter of no more than 11.52, and not less than 9.08 with a 230* cam. Smaller cams can use less starter as can engines with more pressure.
For a streeter, Second gear is where it's at. IMO, 6.82(3.55 x 1.92) is about ideal for a stout SBM, and with a hi-pressure 367 is simply funtastic. But yes, down to 6.20 will still be fun.
But once you get into the 5.xxs; forget the smaller or lower-pressure engines, else just live with it.
At one time I had the seemingly bright idea to run 28s on the hiway and 24/25s in the city. But those small tires just went up in smoke all the time, and because they do not come in wide sizes, my car kept spinning out with the tiniest bit too much throttle. That bs took 295s to cure, which are about 27" tall, so that ended that experiment. From the tallest to the shortest tires is about 10% which is about one rear gear size, but only about a third of a trans gear-size; which are about 36%
Ok so there you have my experiences, have at 'er.
