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Curious What Rear Gears Everyone's Running

RJ Squirrel said:
2.94 in my Roadrunner, great for 2 lane hwy cruising. still only getting 10 MPG with the 440
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I had this same 2.94 rear combo with my 73 318/904 Roadrunner, 73 318/904 Barracuda and 73 318/904 Dart Sports. Never made a hard pass with any of them but they all ate up the highway miles, especially the Roadrunner for some reason.
 
It 100% personal opinion/preference. I have 4.10s and 3.23 in my two. I would not change either. Neither one is better than the other. What driving experiance do you want? The 4.10 is not any faster, but has a higher fun factor on the street.
 
Not a B-body, the plan is to run 4.30 gears in my '69 Dart when completed.
This is behind a 380-horse 360 Magnum crate motor and 200-4R trans. The 0.67 OD in the 200-4R gives a 2.88 final for the freeway.
Sure sounds like a win-win to me.
 
Coelacanth said:
My '70 Charger w/383 Magnum has 3.23 gears w/SureGrip. A buddy has 3.55 and 3.92 gears and I might acquire one of those pumpkins, but I'm kind of leaning towards the aftermarket 3.73's as it appears to be a good compromise between low end and highway driveability...tire diameter is 28". Appreciate anybody's thoughts and opinions on what you'd go with if you had a similar set of specs.
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I'd like to mention that, with my car previously running 3.23 with 255's instead of 275's, and now moving from 27" to 28" tire diameter, going from 3.23 to 3.55 won't make as noticeable a difference considering the tire diameter increase and only one notch stouter for the gearing...
 
Overdrives changed things for many people.
Gearing was always a compromise and in many cases, still is. When we gear it for rapid acceleration, it spins too fast on the freeway, uses too much gas and makes the car a pisser to drive on long trips.
The overdrive transmissions changed that. The overdrive manuals often had a deeper 1st gear than any 727 or 833 too so you could run a 3.55 or 3.91 for quick response from a start yet the .64 to .68 top gear takes the deep axle gearing down well under 3.00. My red car has a 3.55 and a Tremec 5 speed that has a .64 fifth gear. Yeah, that is a 2.27 final drive. I have recorded 15.1 mpg on the freeway but that was in 2022 with a different setup. I could probably beat that today. This is with a 3940 lb car with w-i-d-e tires and a 440/495 mill.

IMG_E9307.JPG
 
cosgig said:
My experience? I had a 3:91 in my 67 GTX, it came with a 3:23. I wanted more off the line performance. My times went from 14:06 to 14:17 with the change. That was totally stock. For fun the 3:91!was my choice……….
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This.
 
I think he had his numbers backwards. Going to deeper gears and his ET slowed down?
 
Kern Dog said:
I think he had his numbers backwards. Going to deeper gears and his ET slowed down?
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Usually there is no change. But yes, it can go in the opposite direction.

And in most street cars the et can vary plus or minus 0.2 seconds with no change. So the difference is likely the variability of all the things that affect et not the gear change. Especially a street car.
 
My 383 charger ( big car, small cubes, big cam) went from 13.90/13.70 with 3.23 all the way down to 13.1 with 4.56, on just one outing. Both versions trapped at 6500. The difference was one ratio used 2 gears, the other used all 3.
 
I've got 3.23 gears with a TKX but mine is the .81 overdrive option. I wasn't sure if the small block would struggle with the .68 5th gear and would require more money spent on 3.55's or 3.91's, so I went with this less common option.

It worked out well. It will torch the rear tires in 1st gear and in 5th 70 mph is approx 2,500 rpm. This is with a 25.6" rear tire. Aceleration in 5th is still strong on the motorways, pulling up hills etc.
20260605_102804.jpg
 
RemCharger said:
My 383 charger ( big car, small cubes, big cam) went from 13.90/13.70 with 3.23 all the way down to 13.1 with 4.56, on just one outing. Both versions trapped at 6500. The difference was one ratio used 2 gears, the other used all 3.
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With a street tire?
 
Normally a 295 50 firehawk, but the faster time was some kind of street strip retread. Both shorties. And both spun. The 383 seemed to enjoy some wheel speed off the line. No torque for dead hooking
 
RemCharger said:
Normally a 295 50 firehawk, but the faster time was some kind of street strip retread. Both shorties. And both spun. The 383 seemed to enjoy some wheel speed off the line. No torque for dead hooking
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Interesting. I’ve probably seen 15 gear swap tests and never seen this kind of a et change. Curious as to the change in 60 ft times. Street tire 383 cars with 3.23s will go 2.0 easy enough. That would put the 4.56 gear on street tire at 1.65. That’s pulling the front tire off the ground territory.
 
Okay..... strip/street cars:
3.91s, with a Detroit locker. 10.5"slicks, 727 4500 tc
4.57s, with a spool a 14x32 slicks. Glide, 5500 tc
4,10s, with a spool and 315/65x15 pro drag radial. T400, 4000 tc.
Strangely, all rpm about the same on the street, due to tire height differences.
Got no clue what gears are in the daily drivers. They all have at least one overdrive trans gear.
 
For an around town and 2 lane highway car I think it’s hard to beat a 3.70/3.73 rear with a 4-speed for all around fun driving and performance. For a Torqueflite car I think a 3.55 works out well with a stock or bit looser than stock converter. By the time you get up to 60 mph or so the converter is tightening up. My 2 cents.
 
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