Any and all thoughts are welcomed
Whoa hold your horses boys, lol.
2500@50mph points to 3.91s
The following are my opinions based on 4 years of trying to be happy with it.
1) 2500 is nearly ideal for fuel economy. Any slower and with the factory type distributor, you cannot give the engine the cruise-timing it wants, to get optimum fuel-economy.
But I gotta agree, 100 miles at 50 mph pretty much sucks.
2) I can tell you that, in the the NON-od gears it easily puts up with 430 hp, and even in the factory Alloy box, altho I fixed the anti-rattle front pin-hole.
3) Another thing that I can tell you, is that any high-winding engine will NOT like the wide gear ratios, at lower rpms. You are gonna need plenty of cylinder pressure to be satisfied.
4) the ratios are; 3.09-1.67-1.00-.73od
the splits are .54-.60-.73
That means that whatever you rev it to, on the shifts the rpm will drop to these percents.
If you are used to the ~.72 splits of the Standard A833, and have a torquey SBM, then you re probably used to shifting at ~2800 around town. If yes then the Rs will fall to .72 x 2800= ~2000. So your engine needs a good amount of torque, to make that doable in each successive gear.
But with the od box, shifting at 2800, the Rs drop to; 1500/1700/and 2050, but you gotta baby it into od, lest that gear shatters. I broke a couple of them before I smartened up. So if your engine has no balls at 1500 to 1700, you are gonna have to rev it higher before shifting. For instance, to come in at the same 2000 as with the Standard box, you would have to rev it to 3700 on the 1-2, and to 3330 on the 2-3 shift.
With 3.91s your roadspeeds are 24mph at 3700 in first and 41 at 3330 in second. 65mph is ~2300
For me, that trans sucked.
At that time, I had an 11.3Scr alloy-headed 367 making about 185psi, with a
[email protected] cam, and was trying desperately to run 3.55s, for 65=2100.
If you are worried about the overdrive box, Passon sold me one of his boxes and side covers, which I have not been able to break
My Opinion is to swap the 3.91s to 3.23s, and get a Commando gearset. It has ratios of 3.09-1.92-1.40-1.00, and splits of .62-.73-.72 super nice.
If you currently have a Standard box with ratios of 2.66-1.92-1.40-1.00 you are already familiar with these splits. And your starter gear is 2.66 x 3.91=10.40 which is quite nice.
To get the same starter with the Commando, you could use 10.40/3.09=3.37s which could be rounded down to 3.23s or up to 3.55s.
3.23s will get you about 65=2600, with a starter gear of 9.98 which is a hardly noticeable difference from 10.40.
At 2600, you can almost give an SBM the cruise-timing it wants, which could be as high as 56*. You can modify the Vcan for 24*, and run an initial of 14* and another 14 centrifugal; for a total of 52*, that's dang close.
I love my Commando box. I got the gearset from Passon. They come up for sale here from time to time.
I wanna say that I would not run this box with a 3.31 stroke engine, but behind my winter engine, a low-compression 318 it wasn't all that bad, lol. But I wasn't looking for performance...... either.
