question about transmissions

hello A series friends my 1969 dodge a100 corey cruiser had motor and trans replaced before i saved it from crushing with a car engine and trans. my question is ..... is there a difference in the a727 torque flight and the a727 load flight output ratios. with the 391 rear gear the engine is screaming at 55 mph with the 14 in tires only able to get 65 out of it with 295 50 15s any help and advice greatly appreciated. thanks in advance

the 391 was used in the 225/6 with a 3 speed
with a auto it should have a 323 rear gear

dix is right. The 3.91 is way too short. I have a 3.23 behind my 727 and I'm running approx. 65mph @ 3000rpm.
That's basically the same as with a passenger car, same ratio at the output.

Get a 3.23 or longer rear axle and you're happy. That should be exactly the same 8.75 as with pass cars as well, IIRC, so you're fine if you just swap the inside of the diff. At least, the pass versions are fine for the A100 load as well. It's not a heavy truck

The output of the third gear is one to one on both transmissions, got to change out the ring and pinion to something more freeway friendly.

well per the id tag on van the 69 corey came with 318 auto and 391 gears but then again it might not be a 727 in it now because the engine and trans came from a new yorker or some such car that the junk yard had

Like Keith said, it doesn't matter b/c there's no overdrive. It's 1:1 in 3rd. Your rear gear is to low for your setup. 3.91 is a pretty short gear. My van came with 3.5 and it would scream at 55+ with the 3 speed, still 1:1 in 3rd. I have a 3.70 rear gear now but with .67:1 overdrive. With 25.5" tires it runs around 2300 at highway speed now instead of 3k+.

With 225/60R15 tires, @ 1:1 and a 3.91 rear end you'll be running 3K at 55mph. It's great for off the line around town though. But you'd be better off with something in the 3.2-3.5 range or lower if you do alot of highway miles and need to keep the rpm's down for your own sanity. It will still scream above 60 though b/c the final ratio is a compromise between get up and go and comfort and economy. Mostly you're stuck with that 1:1 and 2 other gears until you swap to a better transmission. Overdrive is like the best of both worlds and the more gears the better.

http://www.grimmjeeper.com/gears.html

If you want a freeway cruiser and don't mind it being slow off the line get yourself a set of "poor man's overdrive" 2:94 gear ratio gears.

They are no longer available new but you can find them used in good shape on Craigslist or other places.