Will it make much of a difference? 3.73 vs 4.10 gear

[UOP]

Ok, last weekend my stock rear differential grenaded during a wot 1-2 shift and I think it took the trans with it. It now makes weird noises and leaks when it never did before.

Anyway, this gives me a chance to upgrade and I've decided to go with a 8.8 rear and A500 trans. The problem is that I'm not 100% sure which gear ratio I should go with. On one hand, I plan on racing this car alot over the next few years (plan on running full bracket season) so I would like the best accelerating gearset, but on the other hand I love to drive my car and it would be nice to get better mileage with less wear and tear on my engine. I did some math using the gears I'm considering and this is what I came with.

Current (old) setup with A999 trans and 3.91 gears:

Tire size: 26"
1st gear ratio: 2.74
2nd gear ratio: 1.54
3rd gear ratio: 1.00

Shift RPM: 5500
Speed at 1-2 shift: 39.73 mph
Speed at 2-3 shift: 70.68 mph

Cruise RPM at 65 mph: 3285 (SUCK!)
Cruise RPM at 75 mph: LOL!! (3790 if you're curious)



Proposed setup 1 with A500 and 4.10 gears:

Tire size: 26"
1st gear ratio: 2.74
2nd gear ratio: 1.54
3rd gear ratio: 1.00
OD ratio: .69

Shift RPM: 5500
Speed at 1-2 shift: 37.89 mph
Speed at 2-3 shift: 67.41 mph

Cruise RPM at 65 mph: 2380 RPM
Cruise RPM at 75 mph: 2745 RPM


Proposed setup 2 with A500 and 3:73 gears:

Tire size: 26"
1st gear ratio: 2.74
2nd gear ratio: 1.54
3rd gear ratio: 1.00
OD ratio: .69

Shift RPM: 5500
Speed at 1-2 shift: 41.64 mph
Speed at 2-3 shift: 74.09 mph

Cruise RPM at 65 mph: 2165
Cruise RPM at 75 mph: 2495


Right now I'm leaning toward the 3.73's because I don't think there will be a noticeable difference between the two on the track, and if there is it will be minimal. Plus, that's what my currently have (not that a set of 4.10's would put me in the poor house) Looking at the math I'm starting to wonder if I'm over thinking this whole thing. There's only a 4 mph difference in 1st gear shift points and just a few hundred rpm difference in cruising situations. However, this is my "race" car. The whole reason I built the thing was to go racing, I only recently fell in love with just driving it around town.


What are your thoughts?
Sorry for the long post................

 

[67Dart273]

I don't know, but I had a HELL of a time figuring out the Mopar/ Mazda avatar until I scrolled down......................

Have ta give you credit for that one!!

 

[moper]

It seems like with 4.10s you're already a tremendous improvement in cruise and acceleration. I'd go with them. Plus, you can get two IRS diffs and swap just like the 8 3/4. It's not like they are huge money.

 

[mrfttmuscle]

I myself have always been a big fan of the 3.73 gear ratio,one thing I do know is it can be tough to build something that is dubbed street and race , also you talk about getting some more fuel economy.The 3.73 gear is a great all around gear for both the street highway and the track , I had a 71 Road-Runner with a very lightly built 383 that had 4.56 in the rear I can tell you it accelerated to 98 miles an hour very quickly but drank the heck out of gas, back in those days a Texas credit card was needed to be able to have gas to cruise.The cars best E.T. in high school was a 12.2 thru the mufflers and MT street tires. Sorry I got swept up in memories,go with the 3.73 and if you decide it isn't what you want you can always change it at a later date.