I am a little surprised at that, too. But, then I suppose he will be using a Radial T/A type tire that is more for show than grip and that should keep the 8.75" OK for now.

I think this sums it up very well. The car will not be any faster or et any better with a gear change. First gear will be crisper, but other than that, the only difference is what gear you choose to be in.

I did notice that you used the word "optimize", probably not by accident. So if you don't like the engine rpm when you are cruising down the freeway (i.e. it is too low) then a numerically higher gear ratio make good sense.

To determine your final OD engine rpm simply put your information into your favorite online calculator, then multiply the rpm by the OD ratio, i.e. 0.64.

To me much depends on how much street and or race you plan to use it. And as many said with that big Hemi you dont need as much gear as it should have the torque to pull about the same et with lower number gears. Of course if you plan to race it and put sticky tires on it then I would go with a Dana or Ford 9" with the manual trans. I also agree it will work better with a taller tire. I run a 30" tall tire on my 63 with a 440/493 wedge that I am sure makes alot les power then your Hemi and the 30" tires work nice for me at the track and on the street. If you plan to race alot I would go with about a 30" tire and run 3.91's with your combo. Good luck what ever you decide on. Ron

Just say no to a phord 9" in a Mopar.

Danas are super cool and tough and if the OP is gonna beat on the thing hard with sticky tires, it is the ultimate rear. But his 8 3/4 will handle most duties. I have had an 8 3/4 in my Cuda with a 500" Wedge for more than a decade. And now have a 540 Hemi in front of it.

I have hurt a couple of gear sets over the years but that still doesn't amount to the cost of a Dana.

We run 3.91s. Mostly because they are a good compromise between fun and hiway cruising. If we ran more hiway, we would have higher gears. If we raced more, we would have lower gears. But 3.91s are a good match for the way we run our cars.

I also run an 8-3/4 but behind a Hemi with a manual trans if I was going to race it with stickies I would definetly upgrade the 8-3/4 as I think it may break in time behind that combo in a manual trans. I believe the Dana's are actually cheaper then the Ford 9" but I do like a Jackpot rear when it comes to working on them as I like that you can take the jackpot out and work on it on the bench. I want to upgrade to a Dana myself one day if I ever get the money. Ron

I have that tranny in my Dart.

Smallblock stroker,28 inch tire,253/255 @.050
solid cam,RPM Intake.

Started out with 3.91 then swapped to 4.30

My motor is happier at highway cruise with
the 4.30's

Mike

My 2 cents...... 3.91 gear ratio.... And the next time you buy tires go with a 28" or 29"... That should put that 528" motor in the sweet spot...