Rear end gear with 727?

Moparkrazed

Active Member
Local time
5:54 PM
Joined
May 15, 2022
Messages
44
Reaction score
16
Location
Blythewood, South carolina
Hey guys, still thinking out my 71 charger build. I’m still between a 440 and 6.4 but my question is if I go with a 727 would I be able to run 80mph without killing the motor with rpm’s. I think the car has 200 something rear end in it now. Would a 727 be ok or should I swap out to a 4 or 5 speed?
 

RemCharger

Well-Known Member
Local time
4:54 PM
Joined
Apr 5, 2014
Messages
4,828
Reaction score
4,742
Location
Sask
3.23.
Oh, and a 4 speed has the same final drive ratio as a 727. 1:1
 

Moparkrazed

Active Member
Local time
5:54 PM
Joined
May 15, 2022
Messages
44
Reaction score
16
Location
Blythewood, South carolina
Awesome. Thanks for the info! I’m still pretty far out on getting engine and trans but still want to have a direction and also learn more as I go. I appreciate your replies.
 

ruffcut

FBBO Gold Member
FBBO Gold Member
Local time
5:54 PM
Joined
Dec 26, 2016
Messages
1,230
Reaction score
1,865
Location
Elk County PA
Many drag racers use a 727 transmission with 4.56 and steeper gears with no problems. Of course they are usually beefed up for racing, but still retain the same gear ratios as a stock 727. On a side note, my max wedge clone runs a 727 and has seen mph in the mid 130's. ruffcut
 

Moparkrazed

Active Member
Local time
5:54 PM
Joined
May 15, 2022
Messages
44
Reaction score
16
Location
Blythewood, South carolina
Many drag racers use a 727 transmission with 4.56 and steeper gears with no problems. Of course they are usually beefed up for racing, but still retain the same gear ratios as a stock 727. On a side note, my max wedge clone runs a 727 and has seen mph in the mid 130's. ruffcut
I know the 727s are pretty stout transmissions. I’ve never owned one, just have my 904 in the dart and A 903 ( I think ) in my 66 valiant. But the charger I plan on using a lot more and want to do a lot of road trips. So looking for something that has top end without killing the motor with high sustained rpm’s.
 

Fran Blacker

1 of 27
FBBO Gold Member
Local time
5:54 PM
Joined
Sep 23, 2016
Messages
13,863
Reaction score
14,623
Location
Connecticut
If you run 3.23s with 26" tires I'd say 3200/3300 rpm. How big a tire do you need to get it under 3000rpm. Ran 3.54s with 26" tire 3000rpm at 70 mph.
 

Moparkrazed

Active Member
Local time
5:54 PM
Joined
May 15, 2022
Messages
44
Reaction score
16
Location
Blythewood, South carolina
If you run 3.23s with 26" tires I'd say 3200/3300 rpm. How big a tire do you need to get it under 3000rpm. Ran 3.54s with 26" tire 3000rpm at 70 mph.
Not sure on what size I’m going yet but definitely appreciate you letting know what rpm you are turning with ur tires and gear ratio. Definitely helps me out. Thanks for posting that.
 

Thrashingcows

Well-Known Member
Local time
2:54 PM
Joined
Apr 24, 2020
Messages
914
Reaction score
1,466
Location
Northern BC
I've run both 2.76 and 3.23 in my 68 T/C wagon, 440/727, and 225/70/15 tires, and while the hwy cruising with the 2.76's is a little better the in town and low end pick up is kind of poor, and having the transmission constantly jumping between gears from part throttle kick down pressure being low due to lower RPM's is really annoying. I prefer the 3.23's much nicer all around cruising and Hwy gear and the whole car seems to perform better.
 

Cranky

Banned Henchman #27
Staff member
FBBO Gold Member
Local time
4:54 PM
Joined
Dec 4, 2009
Messages
30,295
Reaction score
33,033
Location
Pasadena, Texas
904's and 727's.....and no 903's. Ran a 2.94 behind a 383 and it did good on the highway with 27" tires and wasn't bad in town being a small big block. A 4.56 behind a 340 with 29's was fun in town with a 71 Cuda. Pick your poison. I like deep gears with an OD trans....
 

fourgearsavoy

Well-Known Member
Local time
4:54 PM
Joined
Dec 26, 2011
Messages
202
Reaction score
578
Location
Rittman Ohio
I'd go with 4-speed and 3.23's with a 28" tire. Chargers look good with a larger tire to fill the well.
 

SlinktRR

Well-Known Member
Local time
5:54 PM
Joined
Aug 27, 2012
Messages
1,319
Reaction score
725
Location
Dallas TX
I use 3.23 and 3.55 with 499ci and 28" tire. I like the 3.23 most of the time, around 3000rpm at 80mph which is fine with good mufflers that don't drone. I enjoy freeway blasts with 3.23's, definitely no 2.94 or 2.76.
 

Moparkrazed

Active Member
Local time
5:54 PM
Joined
May 15, 2022
Messages
44
Reaction score
16
Location
Blythewood, South carolina
I use 3.23 and 3.55 with 499ci and 28" tire. I like the 3.23 most of the time, around 3000rpm at 80mph which is fine with good mufflers that don't drone. I enjoy freeway blasts with 3.23's, definitely no 2.94 or 2.76.
Thanks for the feedback on it. I’m leaning 440 around 530 or so hp. I do want some fun around town but don’t want to be scared to jump on the interstate to travel a few states as well.
 

SlinktRR

Well-Known Member
Local time
5:54 PM
Joined
Aug 27, 2012
Messages
1,319
Reaction score
725
Location
Dallas TX
With 500hp you will enjoy the 3.23, can keep up with modern traffic pretty effortlessly. 2.76 is just too tall for even a stout motor.
 
Top