3.91's too much?

[Bandit72]

i have recently found the 8 3/4 housing for my charger, and i already have a set a 3.91 suregrip chunk for it...i was just wondering if this might be too much gear for my stock 400, it has been rebuilt about 20,000 miles ago and will probably only see 100 occasionally (less than once a month) and probably not any faster than that...i mostly want some more "umph" out of the hole  and still be able to pass people on the highway without over revving my engine....what do you all think. (In about a year the 400 will be replaced with a mildy build 413 or a really well build 451 stroker...)

later 

[Ghoste]

Use it.  I have 4:10's with a 383 and I'm happy.

[70kracken]

i have 4 10's in a dana in my charger, and i'm real happy with them.  if you're wanting some freeway action, 3 91's may be a bit to much for you.

[RD]

i have 4 10's in a dana in my charger, and i'm real happy with them.  if you're wanting some freeway action, 3 91's may be a bit to much for you.

freeway's!!! in Kansas!!! BWHAHAHAHHAHAHHA!!!

j/k... 3.91's equate to 2800 rpm at 60 mph.  You ready for that?

[phat69charger]

Try this, calculate what you have!   http://users.erols.com/dmapes/GEARCLC.HTM

[sext7366]

yeah randys ring and pinion has a good calculator also www.ring-pinion.com I would calculate what you have now then see the difference with 3.91's I have heard a 3.73 is about as high as you'd want to go if about half of your driving will be on the highway. 3.55's are a good compromise but I think I'd go with the 3.73's personally just so I am not dissappointed.

[Brightyellow69rtse]

4.10s here in the dana, i switched from 235 60 15s to 275 60 15;s in the rear and i was happy with the difference it made on the highway  .......Mike

[firefighter3931]

Yep, 3.91 or 4.10 is a great street gear...especially with a 28in tire. 

Ron

[8WHEELER]

I have been back and forth on this fence. If you can stay at 60 and not have to maintain a steady
speed for just short periods of times, 391 are a great gear I also run 275 60x15. But when I run from
here to Canada over 100mi each way, and most of the people I drive with have 5sp and 6sp with
overdrives and like to run 70 and 75 the hole time. Well I got tired of running over 3k just to keep
up and there doing 2k and getting much better mileage. So I put my 355 back in. It does depend
on how you drive and who you drive with you have to consider as well.

Dan

[firefighter3931]

I have been back and forth on this fence. If you can stay at 60 and not have to maintain a steady
speed for just short periods of times, 391 are a great gear I also run 275 60x15. But when I run from
here to Canada over 100mi each way, and most of the people I drive with have 5sp and 6sp with
overdrives and like to run 70 and 75 the hole time. Well I got tired of running over 3k just to keep
up and there doing 2k and getting much better mileage. So I put my 355 back in. It does depend
on how you drive and who you drive with you have to consider as well.

Dan

Those are good points. I just wonder what it was like back when these cars were new and evryone ran stock 26in tires ? Were people really freaked out by 3k engine speeds cruising down the highway ? I like the 3.91's with a 28in tire because it yields a 3.63 final drive ratio which is pretty close to the factory 3.55 with 26in tire combination. Engine speed doesn't bother me ; most of mine are happier above 2500 rpm anyway. If it gets too loud i just crank up the Aerosmith 

Ron

[Fore40]

I switched from 3.55 to 3.91's with a 26.5" tall close to stock size tire, this combo is not good if you like to take longer trips like 30 min or more on the freeway. The 3.91's were fine around town but hated them on the big road after a few hundred miles I switched back to the 3.55's.