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Discussion Starter #1
Getting close to being done with my LS build. 1970 Nova LS3 (441rwhp/404rwtq) tko 600 (2.87 1st/.64 5th) 28” tire, 8.5 inch 10 bolt. I currently have 3.42s in the car. Definitely seems like 1st gear is a little long and I want a little more pop off the line. The car is a street car, will never see the drag strip. I’m leaning towards 3.90’s. I also considered 4.10s. Leaning towards the 3.90s more though (although they might whine), I don’t want to be spinning hard every time I punch it off the line. Any thoughts/suggestions/advice? Anyone with a similar set-up? Likes/dislikes?

thanks!
 

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With an overdrive like that I would definitely go 4.10. You should still be able to run a low rpm down the highway in 5th gear.
 

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2004R with lockup, .68 4th gear. 27" rear tire dia. Went to 4.10 from 3.73 and I like it. 2500 - 2600 ish RPM at freeway speeds. I live in an area where I'm on 2 lane roads a lot, my motor feels happier.
 

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Depends on how you use it. But I'd say 4.30 or 4.56.

The overdrive negates the deep gear for highway driving, but a good 3.5" aluminum driveshaft is needed to keep thngs smooth. And given the 6500+ rpm potential of a cammed LS, the deeper rear gears let the engine get in the meat of the power (say, 3800-6800) and rip.
 

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Discussion Starter #6
Pmotion.... what engine are you running and is 1st gear usable? Spinning tires at every throttle blip or are you hooking up?
Thanks!
 

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I've got a 350 Vortec style small block crate motor, it's a ZZ430 clone. Low gear ratio is 2.74 with a 2600 rpm stall converter. It goes thru 1st gear very quickly. I don't have wheel spin problems unless I WOT from a stop. My car has Cal Tracs bars and springs. My rear wheel HP is more like 300.
 

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I’d start out with the 3.42s and see how it runs and take it from there.. I don’t know what you had for an engine previously but with a nearly square 400+ hp/tq numbers that thing should not have a problem taking off.. I would just wait and see how it behaves with the new mill before swapping gears. It might be just right.. What size tires are the rears going to be? I know you stated 28” diameter but what’s the actual tire size?
 

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For reference I had a 2010 Corvette for a while. It had a LS3, 6 speed with a 0.50 overdrive, and a 3.42 rear. Car felt right and I could get 29 mpg of easy commuting. Obviously aero plays into that a large amount.

With all that being said my 67 is getting a 5.3, t56, and 4.11s. Can't go with 3.73 or 4.11 in my opinion.
 

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Rear Gear

My 66 Chevy II weighs 3059 lbs. LS3 with 4L65E overdrive. Coan lock up TQ. 12 bolt 3.73. 245/45/17 rear tire (25.8" dia.) 2180 engine rpm at 70 MPH. 22 MPG.
 

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My 66 Chevy II weighs 3059 lbs. LS3 with 4L65E overdrive. Coan lock up TQ. 12 bolt 3.73. 245/45/17 rear tire (25.8" dia.) 2180 engine rpm at 70 MPH. 22 MPG.
What’s the 1st gear and overdrive gear ratio on the 4L65E..? I know that 700R4 and the 4L60 share the same gear ratios. 2180rpm cruising at 70 is awesome..
 

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Overdrive Trans

What’s the 1st gear and overdrive gear ratio on the 4L65E..? I know that 700R4 and the 4L60 share the same gear ratios. 2180rpm cruising at 70 is awesome..
Same as 700R4 and 4L60E. 3.06 First Gear and .70 Fourth Gear. Engine and trans require a tune by someone who knows what the hell their doing !
 

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My 08 corvette with ls3, 6spd. auto (4.03 1st gear) 27 in tire and stock 2.56 rear gear. Will toast the tires from a stop without traction control. At 90 mph i'm turning 1950 rpm. Cruising 70 mph it gets 31 mph. C6 advertised 12.9s in the quarter. Seat of pants, it feels faster tan my Nova in the quarter (it's never been at the track). My Nova at the track runs 12.07, with 4.10s and gets 21.7 mpg cruising 70 mph.
 

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My wife had a 11 (LS3) 2SS M6 with 3.42's and currently has a 16 (LT1) 2SS M6 convertible with 3.73's.

I like the 3.73's better. Better everywhere in every gear, less having to downshift. :yes:

I have a 4L80E and locked up with 4.30's and 275/60 MT ET Pro's at 75/80 I'm in the 2800's.
Big change over the 3 speed th350 that was like 50's.:D
 
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