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Which rear gear for my setup?

  • 3.42

    Votes: 6 16.2%
  • 3.55

    Votes: 20 54.1%
  • 3.73

    Votes: 11 29.7%
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Discussion Starter #1 (Edited)
It's time for me to get the Dana 60 rebuilt. My car is a '74 with stock LS2 / 4L65E and (currently) 245-60 rear tires (will be going to 255's at some point).

The rear end came out of a drag Nova and has 4.10's in it. That's low for the street, and with the 4L65's granny first, it's *really* low - changes from 1st to 2nd at 5 MPH or less if I'm not getting on it.

Anyway, I'm changing out the gears and wanted some opinions on which ratio to go with. I've settled on 3.55, but that's not in concrete. However, I'll only consider 3.42 or 3.73 as alternates.

Car will mostly be used for cruising. The 4.10's actually haven't been bad around town, but the RPM's start climbing after 60 MPH and I don't like going past 65 MPH with the low gears.

I'm looking for a compromise that keeps that blast at takeoff while still being able to hold it at 70 MPH or so on a long trip.

I like the idea of 3.42 but I'm afraid that will take too much away from the standing starts. The 3.73 should have plenty of takeoff, but it's only a 10% reduction in RPM. So, the 3.55 seems about right. That's 15% less RPM at 60 than I see now. Does anyone feel *strongly* that I should go just a little higher or lower than this?

Please respond with your opinion on why I should go with the ratio you selected.
 

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04-06 GTOs (LS2 for 05-06) have the same trans you have and they run a 3.55 rear end gear. But a lot of guys upgrade to a 3.73 for better acceleration. Also, I think your tires (15 inch wheels?) are a little taller than the stock GTO tires.
 

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Mike - 74 Nova Baltimore, MD
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For your goals, I voted for the 3.55 gear ratio with your 4L65E transmission.
With the transmission's 1st gear ratio of 3.06, your Nova will still feel decent from a standing start... and with a .69 overdrive gear and a 26" tall tire, your RPM's will be about 2217 at 70 mph (2375 at 75 mph).
 

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My 1st gear is 3.38 and my 5th gear is .62. I just installed 3.73 gears replacing 3.42s and love it. Better in every gear. Not too low for my 3.38 1st gear and OD works great. 2nd, 3rd and 4th are great too.

My motor is putting out about 350 HP and 380 lbs tq at flywheel. My rear tires are 27". Not sure what ratios you are working with but hope this helps you evaluate.

Also here's a great tool that Deryl Atanasu shared with me.Hope it helps.

http://www.wallaceracing.com/gear-speed.php
 

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1969 Nova . . 2dr . . Chino Valley,Az USA
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rquad ...... I say/voted : 3:42

but, I'm a T 5 5speed : 3:97 = 1st .... 0.72 = 5th .... using stock 3.08 rear. (and, I know -- a 250 / 6).

But, GAS ain't going down --- and, it never will .... :eek:

with that said, I think you'll be wanting too go places in your "New Nova" ..... that means 'HiWay Driving'.
The more i drive w/my od gear & gas mileage (last month : 383 mile round trip & got 21.9 mpg) , makes me feel better. and, let me say that I still have good power on the road in the lower gears.
I have two other rear - ends (complete : 1- 8.2 : 1- 8.5) .... that if I change out my rear ... then, I'll build-up one of those units.

But, for now ... I'm liking my 'high-gears'.

you asked ... that's my story ... I'm sticking too-it .
 

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Discussion Starter #7
So far, there's a pretty good split between the three choices, which underlines the difficulty I've had in making this decision. The majority, at just under 50% so far are agreeing with me in leaning toward the 3.55's.

It's a compromise no matter what. Too bad it's so expensive to change your mind once you've made your choice.
 

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FYI Dana 60's don't have a 3.42 ratio. I voted 3.54 (3.55) gears. This is the tallest gear for the dana 60.

3.54
3.73
4.10

Miles
 

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1969 Nova . . 2dr . . Chino Valley,Az USA
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FYI Dana 60's don't have a 3.42 ratio. I voted 3.54 (3.55) gears. This is the tallest gear for the dana 60.

3.54
3.73
4.10

Miles
Miles ... thanks for the info === then, 3.36 ?

rquad ... That's what I mean by having another complete diff .... I can keep my 3.08's and not get hurt. Tho, that ain't much from a 3.08 to 3.36's. Keep thinking about it ...... you'll do good .
 

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Discussion Starter #12
FYI Dana 60's don't have a 3.42 ratio. I voted 3.54 (3.55) gears. This is the tallest gear for the dana 60.

3.54
3.73
4.10

Miles
Must be a difference in the stock Dana like I have and the Moser aftermarkets because Moser lists a 3.42 option. Regardless, looks like that reduces my choices to just 3.55 (or whatever the exact Dodge equivalent is) and 3.73. I think the 3.73's would be too low unless I could fit a really tall tire to complement them.
 

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I can only tell you what I did. I'm running a 285 x 35 x 18 rear tire with a 700r4 and I have 3.55's. After almost 4,000 miles if I had to do it over I'd do the same thing.
 

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I have a .68 OD with 255 60 15 tire and 373 and just enough rpm at 70mph for my cam.

If you're not worried about maximizing performance go with a 354.
 
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