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so which gearing to choose for a rear end?

Started by Drache, February 13, 2012, 01:42:05 PM

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Drache

So I picked up an 8 3/4 rear end for the dart, now I just need to figure out what gearing I need for the Dart. The car doesn't do a whole lot of highway driving although I do drive it from one show to the next. I am planning on taking the car to the strip here this year just for shits and giggles. What do the gurus think?  :shruggy:
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FLG

Need more info..what engine, cam, transmission, and if auto what converter?

Drache

Quote from: FLG on February 13, 2012, 02:01:26 PM
Need more info..what engine, cam, transmission, and if auto what converter?

currently 318 with 904 although the 904 is being swapped to 727 next year. No idea of cam or converter as those were installed before I got the car.
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Nacho-RT74

IMHO, 3.55 uses to be the best all around gear
Venezuelan RT 74 400 4bbl, 727, 8.75 3.23 open. Now stroked with 440 crank and 3.55 SG. Here is the History and how is actually: http://www.dodgecharger.com/forum/index.php/topic,7603.0/all.html
http://www.dodgecharger.com/forum/index.php/topic,25060.0.html

404NOTFOUND

That's the kind of use my Charger gets. I've got 3.54 gears and find them perfect overall.
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Chryco Psycho

the best way to do this is make sure where the car is used the most it is in the powerband of the engine , you should be able to feel where it is happy rpm wise , & then mathmatically knowing tires size & RPM you need to run at determine the best gear choice at the speed u usually travel

68X426

Quote from: Chryco Psycho on February 16, 2012, 10:54:55 AM
the best way to do this is make sure where the car is used the most it is in the powerband of the engine , you should be able to fell where it is happy rpm wise , & then mathmatically knowing tires size & RPM you need to run at determine the best gear choice at the speed u usually travel

http://vexer.com/automotive-tools/speed-rpm-calculator




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64dartgt

I had Motive 3.55's, which were noisy as hell and swapped in a good set of used 3.23's and am much happier.  Quieter and much better for all around cruising.  I felt like the 3.55's were a bit much and the car really isn't a tire smoking monster anyway (rebuilt 71 Hi Po 340 probably making about 300 hp tops).  Of course I know I have a rebuilt stock converter in the rebuilt 904, so I might be limited there.  If I were you I would pass on the 727 and go for the OD upgrade.  I was debating it when I have my 904 rebuilt, but it seemed like too much of a challenge.  Since then the tranny mount has been worked out by several people and from a clearance perspective you really just need a BF hammer and five minutes of attention to the tunnel.  Then pick your gear set.  In hindsight I really wish I had taken that path, but oh well.  I will murder the 904 in a few years and move on.

471_Magnum

I'm always amused by folk who are willing to give gear ratio advice with no supporting information given. ::)

As stated previously, tire size, converter stall, cam, performance goals and intended use all factor in to the calculation.

3.55s are a great gear for a car with 28" tires that sees occasional extended highway use with moderate cam and converter. I currently run them in my Roadrunner... with 27" tires, a 2800 stall converter, and a well balanced motor. It'll have 2.76's in it for the Power Tour though.

You can make up the difference between 3.23s and 3.55s with tire size selection. Running 3.23s with typical A-body size (26") tires is about the same as running  3.55 with 28" tires (popular on B-bodies).

~3200 rpm seems to be the approximate threshold for sanity when it comes to cruising rpm. It's by no means a rule though. Engine balance, exhaust resonance factor in.

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