OK guys, this has been asked (and answered) at least a dozen times already, even by me, but hear goes.

Concerning the Charger: 4,200 pounds, 440 modified to a bit over 500 HP, modified TF 727, 3000 stall converter. Currently running 3.23 rear.

Odds are slim the car will be raced again.
Primarily a cruiser / street car seeing highway time.

The engine's power band is approximately between 3000 - 6000 rpm.
Normal street cruising and highway rpm = 2000- 2500.

Clearly not usually getting into the power band.
Seriously considering going to 3.91 gears.

Street would be about 1877 rpm @ 40 mph,
highway, about 2815 @ 60 and 3284 @ 70 mph.
Theoretical top end about 132 @ 6200 rpm.

The car is still fun to drive, but with the 3000 rpm power-band and stall, it can be a little "sluggish", until you get on it - then all hell breaks loose.

Not too worried about the drop in gas mileage (only average about 1,000 miles per year), but more about wear and tear on the engine.
(Yes, the engine was properly balanced and blue-printed.)

And thoughts would be appreciated.

Archer

 

Have fun ! put a 3.91 in it .. & some 29" tires

 

I would do the 4.10 and leave everything else alone... Just my 2 cents...

 

I think tires and overdrive when I think final drive ratio.

If you stay with a 3.23 going to smaller tires to get quicker take off is not possible. That much power will eat them.

With the 3.91 you can go bigger to get lower highway rpm's and better fuel economy.

 

Guys -

Thanks, I think the L60s / 275s are the biggest that will comfortably fit without clearance problems. Going smaller just doesn't fill the wheel wells enough (like I said, it's a cruiser, so looks count).

The concern about the 3.91s would be over revving the engine, especially on the highway.

Coronet - the OD would solve the problem, but that's out of my budget right now.
The gear change is do-able.

Any recommendations on brands to look at/avoid?

Thanks,

Archer

 

Guys -

Just catching up.
Can't believe this thread is 4 years old.

Finally pulled the trigger on the 3.91's last year, and after driving around for a while, all I can say, is I should have done it sooner.
Doing about 3K @ 60mph on the highway and the motor seems very happy.

Bob -

You were probably right, the 4.10s wouldn't have been a problem.

Archer

 

3.91's is a good safe choice.... 4.10 Maybe just a little more of a neck snap from the stop light...
Glad your happy with the change.... That's really all that matters.... Rite?

 

I agree, I'd go 4.10's.

 

A little late to the party here, just reading up on some old posts, as I just joined.

I read a lot about 3.91's, 4.10's and similar ratios being too much for the street. Heck, they were factory installed when muscle cars were new! In the late 70's, I had a 70 Challenger R/T, 4spd and factory 3.91's. I guess it depends on the roads in your area, but I loved it. I lived in Philadelphia (Roads kinda limited.), plus the speed limit back then was 55.
If I lived somewhere, like say, Wyoming, I can see a longer gear being nice. I used a 2.93 for road trips. Gas mileage was much better. It ran 14.40's with the 3.91 and 15.20's with the 2.93, on L60-15 street tires.

Newer cars have us spoiled, having overdrive transmissions. Plus newer cars have a lower torque curve to take advantage of the OD. It seems like they're revving too high if not in OD. I would've killed for a 833 with a overdrive 5th!

And yes, the Challenger is the one that got away. :-(

 

Speed -

To be honest, on the STREET, the difference between the 3.23s and 3.90s is almost hard to notice. But on the highway, the 500 rpm bump is noticeable. However, so are the burnouts, err..I mean launches.

Welcome aboard.

Archer