New Rear Gears

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cwatts

cwatts

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I want to run a lower gear in my Dart. I currently have a 3.23 and 15" tires and it cruises well at 55 mph at about 2500 rpm. I'm thinking of a 3.91 or a 4.10. Anyone run gears this low on the street ? also would you suggest just buying a new ring and pinion or the whole chunk assembled ? Thanks
 
Depends on what kind of driving your doing? If your just cruising around town and a short run on a interstate rarely then go with the 4:10. If you go on long drives a lot then stick with what you got. Maybe a 3:55.
 
What does your cam require? What transmission are you using (and stall if auto)? What do you plan on doing with the car? 3.55 is a damn go balance between take off and cruising! Also know that you can now get 3.73 gear ratio for the 8.75 rear (which I'm assuming you have/are using), which also a great balance between 3.55 and 3.91. Why mopar didn't offer it from the factory I don't know.

One other thing, have you thought of using an o/d transmission?
 
I am running 4:30 on the street with a 29 tall tire and its not bad. I stay off the freeway as much as possible and take main hiway when I need to go across town. But this keeps me driving slow to avoid tickets as every time I take it out of the yard I end up with either cops behind me or some old fart wanting me to pull over to here about the one he had in his GLORY DAYS
 
If I did a lot of cruising a o/d transmission would be a no brainer. We just finished the drive train in my dad's car and he is kicking himself for going with a 4 speed.
 
I forget the specs on the cam but it is very lumpy with a great idle. Trans is a 727 with a 3000 stall. I mainly just cruise around town with minimal highway driving.
 
Go for the high gears of 4.10 or better.
If you go to Dr.Diff, or Mancini racing, you can purchase the center section all done for approx. $1000 or so dollars.
 
I have a 4.10 sure grip 489 chunk i can sell if you go that route
 
Thanks Craig, just bought new super stock springs and new offset hangers as well. I think I'm going to buy the whole chunk brand new from Mancini here in Michgan and go with the 4.10 and keep the 3.23 chunk if I'm going on a highway trip. Also eyeing up a set of roller rockers good for 25-30 horse.
 
I'm trying to do the same thing to my Cuda since I put the bigger wheel and tire combo on the back last year my actual ratio has got to be somewhere around 2.9 so I am loking for a 3.91 chunk to swap in and out with the 3.23 I have when I'm not driving too far on the highway .Either that or a 3.73 that I could probably just leave in for the highway , 28 inches is quite a bit bigger that the 245/60/14 I used to run .
 
With a 3000 TC, it would be hard for me to justify anything more than 3.55s on the street.
-Think about; Youre cruising along at 30mpg in 2nd doing just about 2000 rpm. Things are pleasant, but youre ready, no itching, to pull the trigger. You see your opportunity. Hammer down! The tranny kicks down as the TC winds up. Bam it hits. 30 mph in first is about 3500rpm. the tires light up and you are g-o-n-e.- 3.73s would up the launch to 3700. Anything more than that is overkill, IMHO, for street. I mean if you shoot a skunk dead with the first shot, why waste more bullets on it. In less tha 2 seconds you will be speeding, if you arent already.
-And 3.91s are a miserable ride at anything over about 55mph. Take your son to a car show? Maybe once. You may be having fun. Him not so much. Or the wife? Forget that! Just saying. Two-chunk system? Been there. Seemed like a good idea. That novelty gets old in a hurry. 4-speed auto? Now yer talkin!
-But I digress. I can tell from your excited responses, that you have pretty much made up your mind on the big number gears. So yeah, better to buy a complete chunk. Then you have something to fall back on when you just cant stand it any more.
-Without an O/D tranny; just to reiterate; " 3.55s are about as good as it gets" Who said that? Rusty I think.And Doogie.
 
cannucky said:
I'm trying to do the same thing to my Cuda since I put the bigger wheel and tire combo on the back last year my actual ratio has got to be somewhere around 2.9 so I am loking for a 3.91 chunk to swap in and out with the 3.23 I have when I'm not driving too far on the highway .Either that or a 3.73 that I could probably just leave in for the highway , 28 inches is quite a bit bigger that the 245/60/14 I used to run .
Click to expand...

Chris, i just bought mine from Mancini Racing here in Michigan. $1300 brand new with the Auburn posi unit. Not a bad price in my opinion.
 
$1300....WOW!! It's almost cheaper to do what I did, 2004r overdrive automatic. 3:90 gears. I can cruise down the highway at 2300 RPM doing 65/70 MPH with 29 inch tires (29 X 15 X 15). I spent about $1800 including the trans overhaul and TCI adapter. Did all the install and fabrication myself. Now I get great gas mileage (highway-20MPG) and have a pretty decent launch (only have a 1800 stall). I love it and it will save me on gas forever!!!!

treblig
 
I just had RRP do my late A body 8 1/4 with 3.73 & shur-grip. 273 W/904, stock converter and Transgo 2 shift kit. Tires TBD but will be the biggest 15" that will fit in the wheel well without rubbing the sidewall on the springs. :burnout:
 
I checked the calculator and the difference at 65 mph between my old 245/60/14 with the 3.23 and the new Nitto 275/60/15 with a 3.73 is 161 rpm -2852 to 3013 - and with a 3.91 its 307 rpm 2852 to 3159 so yeah I think I can live with either one . The 2 pig idea is for cruising long distances then swapping for a few days while I'm there then swap back for the cruise home , the 3.23 just doesn't have the oomph around town with the big tires .
 
cheaper to piece together a new chunk with new parts. I can make two chunks for 1300.
 
I'm not spending 1300 bucks thats for sure ,I traded a pair of good ready to run stock 360 LA heads with the upgraded springs and a converter to a guy for future parts and am trying to work it a third way to another guy who wants an 8 3/4 housing and a 360 block from the first guy with me throwing a cam in the deal to the third guy for a good sure grip chunk with either the 3.73 or 3.91 depending on what he can scrounge up , gotta love these no money deals -everybody gets what they are after the spare parts get used and everybody is happy -hope it comes together eh LOL !

PS yes they are both great FABO guys .
 
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