Surprise! Now what...
It pulls like a train but drops back to 2300
I run a 4spd, and so I get about 2300 rpm of 'fun' before having to shift.
Instead I wind up rowing through the gears or just skipping 2nd altogether
5800 less 2300 is 3500rpm, so I'm a lil confused.
The regular 4 speed will drop from 5800 to ~4180 or 1620 rpm
(5800less 2300)/5800 is 60% and that points straight to a very wide ratio box, and the only Mopar box I know of, that is like that, is the A833-OVERDRIVE box, which has very wide splits; and the 3.91s stack them real close together. A lower number rear gear will spread them out.
Maybe this will help;
IMO you might like one of the "regular" boxs better. the standard ratios are
2.66-1.92-1.40-1.00 and the new splits are .72-.73-.71 much tighter compared to
3.09-1.67-1.00 -.73 with splits of............ .54-.60-.73
Lets say I guessed right that you have an overdrive box. and lets put the ratios into road gears with the 3.91s. And I get;
12.08-
6.53-3.91-2.85od
The fact that you say you can skip second gear, tells me that 6.53 is too low a gear for you and first is carrying you high enough to grab 3.91 third gear. And the fact that your engine is pulling 3.91 third gear from 1850ish@38 mph, tells me that's a heck of an engine.
Ok so then, you need a properly working second gear, and my money is on something between 6.53 and 3.91. Lets try something in the 5.xx range; say 5.30. and that points to a 2.76rear gear. The new road gears would be
--7.34-5.30-3.86-2.76 compared to the current
12.08-
6.53-3.91-2.85od
Ok but 7.34 is kindof a clutch eater so lets swap to a Commando box, which has a 3.09 low gear, and the rest are the same. Your new roadgears are
--8.53-5.30-3.86-2.76... compared to the current
12.08-
6.53-3.91-2.85od There yago.
Notice how third and fourth are about the same, and second is better than the current second which you are occasionally skipping.
Ok so now, your rpms will drop to .62-.73-.71. If you shift at 5800, then these are to 3600 into second,to 4234into third, and to 4120 into fourth which will now take full power.
Yeah first will be doggier but com'on; 12.08 is a race starter-gear .
Ok so lets look at the speeds with a 5800rpm shift. First the current box with 3.91s, you will be topping out at
37-71-119-164.. From 37 to 71 is 34mph, and from 71 to 119 is 48, and from 119 to 164 is fogetabowdit. Ok so
remember 34/48/xx
Next with the Commando and 2.76s you will be topping out at
55-88-121-169.. Again third and fourth are very similar, but first gear now goes 49% higher, and second goes 24% higher. You wanted higher, right? Well here it is.
From 55 to 88 is 33mph, and from 88 to 121 is 33mph. You wanted tighter? here it is.m Now
remember 33/33/xx
Ok but say you wanna stack 'em closer together put the 3.91s back in and run the 2.66 box.
The new road gears are
10.40-7.51-5.47-3.91 compared to the current
12.08-
6.53-3.91-2.85od ..You See that 5.xx in the mix? Now it's third gear. And the roadspeeds will be
45-62-85-119 from 45 to 62 is 17mph, and from 62 to 85 is 23mph, and from 85 to 119 is 34 mph. That's pretty tight; you'll be blasting thru there so fast, you might not be able to keep up lol. Now
remember 17/23/34
Personally Ima thinking the overdrive might not be so bad for your combo, but those 3.91s are just too much. Lets see what that box looks like with 3.23s. The roadgears are
9.98-5.39-3.23-2.36 .. compared to the current
12.08-
6.53-3.91-2.85od
See; I put that 5.xx into second again. Still at 5800, the roadspeeds will be
47-86-144-***. from 47 to 86 is 39mph, and from 86 to 144 is 58mph. now
remember 39/58/xx. I was wrong; that box is just crap.... for your combo.
Just trying to be helpful here.
xxxxxxxxxxxxxx
I ran that od box behind my 367HO for one summer which was too long;and then I got me a GVod to split gears. That was a sweetheart deal on the upshifts; but with 3.55s in the back, that 367 did not like the wide ratios, and splitting All-The-Time,really became a nuisance. Plus I broke two of those od boxes. So I was done with them.
Currently I use the Commando and 3.55s. The roadgears are;
10.97-6.83-4.97-3.55 and the roadspeeds are (5800shift) 43-68-94-131. The spreads to
remember are 25,26,37mph.... Works real nice in my combo. She hit 93 in the Eighth at 3467 pounds
Happy Hotrodding
