I thought about the same thing....2500 is approx 70MPH now. In texrock (texas) our tolls are posted 85mph now so lower gears would be awful for me without an overdrive.
70@3100 with 4.11 /31's
56@2500 with 4.11 /31's
The cam in your 401 sounds fairly mild which means that sucker should be cranking a ton of low end TQ out. I would think that 4.11 with an Overdrive will be great. My thoughts are on a 700r4 or a 4L80E with the .71 OD gear, the lower 1st gear in the 700r4 would add even more off the line punch especially if coupled with a good 2400 stall and triple disc lockup clutch. Then we would have all the power through the gears plus can kick up to OD/lockup in 4th.
700r4 has a 3.06 1st gear compared to our 727's 2.45
OD is .70
plus the 700r4 has lockup in 2nd,3rd,4th gears eliminated all friction and losses in the converter at speed, this lops another 2-300 rpm off especially below stall speed.
So in OD with lockup engaged your 3100 rpm would reach approx 105mph with 33's
2200rpm would cruise all day at 75. The grunt of that 401 should have no issue pushing the jeep along comfortably at 75.
Figure a stock 360 made 285tq@1500 rpm so the 401 built will kill that@2200
Another option i looked at is swapping the gear sets inside the 727 for a 2.7 first gear unit.
I mean right now our 2.45 first will hit 55mph@5000 RPM in 1st!
So for most of us that means we mash the go pedal in 1st and then let out just skipping 2nd to 3rd to cruise.
A 2:45 1st combined with the 4.11 rear will hit 45mph@5000
Swap in a 2.7 gearset with a 3.73 gives us the same 45@5000 in 1st. But lets us retain 3.73 ratio for the highway.
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