3.23 to 3.55 swap

[wilsonlar1]

For anyone out there that has made this change, is there a noticeable difference changing from 3.23 to 3.55 gears? I will be installing a sure grip at the same time.

 

[mopar 3 B]

You will not go as fast but you will get there faster. Gas mileage wise I have gotten better with lower gears all depends on your application.

 

[Fran Blacker]

It helps. Had 8.75 w/3.23's open rear hit the gas at slow roll big trail of smoke. Went to 3.54's in a Dana w/suregrip then could put the power down that made difference. Last summer put 8.75 in w/the 3.23's after 30 years of sitting made noise pulled the 3.23's now I had a 4.10 put that in big jump. Instead of a chirp 1st to 2nd (auto trans) would spin the tires. If you drive any distance to much gear.

 

[wilsonlar1]

It helps. Had 8.75 w/3.23's open rear hit the gas at slow roll big trail of smoke. Went to 3.54's in a Dana w/suregrip then could put the power down that made difference. Last summer put 8.75 in w/the 3.23's after 30 years of sitting made noise pulled the 3.23's now I had a 4.10 put that in big jump. Instead of a chirp 1st to 2nd (auto trans) would spin the tires. If you drive any distance to much gear.

I'm looking for a setup that will give me a better jump off the line for the rare race. My engine is a 383 that is built pretty strong and I think the gears are holding it back.

 

[wilsonlar1]

You will not go as fast but you will get there faster. Gas mileage wise I have gotten better with lower gears all depends on your application.

My application is an occasional race but mostly cruising. I do like to get from one stop light to the next, quickly. I'm just wondering if the difference between the two is enough to invest in.

 

[Fran Blacker]

I had a 26" tire with 3.55's , 3000 rpm 65/68 mph. If you have an open diff now and spin right tire it will make quit a difference, IMO. Next step is 3.73's = more rpm, top end of cruising gears. I'd go to the 3.55s my opinion. Keep watching thread there will be plenty of in put.

 

[SublimeSixpack]

I think you'll like the 3.55 gears, especially at your elevation (Denver). Is it worth the money? Only you will be able to decide that. Personally if I were you I'd buy another 3rd member with the 3.55 gears and Sure Grip and slip it in and see what you think. Keep your current 3rd member with 3.23 gears in case you want to switch back. You won't have any trouble selling the 3.55 unit if you decide it's not for you.

 

[oldbee]

IMHO- jump to 3.73. 3.55 isn't much diff over 3.23.

 

[forphorty]

What torque converter do you have? A switch from a stock converter to a good performance converter will improve acceleration more than a switch from 3.23s to 3.55s. But yeah, you need a sure-grip in there.

 

[Kern Dog]

The difference is very slight. Add up the cost, too. A new Auburn LSD is almost $400. Gears, bearings and the install kit is going to be $300+. Then the labor cost to set it up...
The 3.91 ratio will make a noticeable difference though. I had a 3.23 open diff in the Charger when I first swapped in my 1st 440. The car would break loose at a 30 mph roll, spinning the one tire to 80 as long as I wanted. I had a noisy 3.91 SG that I had in the car with the stock 318. The whine was annoying so I yanked it. For fun, I swapped it in to see how the car felt. Screw it...I was hooked on the instant throttle response and sideways burnouts. I later had the diff rebuilt and went with 4.10 gears.
If you have some free time, consider searching for a rebuildable clutch type Sure Grip unit. I am sold on these! They use replaceable friction discs and can be rebuilt over and over when the clutches wear out. These differentials fit any 8.75 case.

 

[440fish]

Im swapping my 3:23 to 3:55. Got out of my car with 3:23 and immediately into my buddies challenger with 3:55s. Similar engine builds. Immediately noticed the difference.

3:55 is way snappier off the line yet still tolerable on the highway.

 

[vintage chromoly]

I'm changing from 3.23 to 3.73 at present. I didn't think 3.55 would be worth the effort.
Time will tell

 

[Ranger16]

I love my 3.23

 

[rumblefish360]

For anyone out there that has made this change, is there a noticeable difference changing from 3.23 to 3.55 gears? I will be installing a sure grip at the same time.

I did that gear swap. I think the best way to describe it is;
The difference in accelerating felt like a good tune up.
Top end slightly reduced.
Fuel consumption slightly increased because the secondary side tips in sooner. Slightly higher cruise rpm.

Would I do it again? Well that depends. 1st, am I looking for a performance gain? I say it isn't much at all. Going from a 3.23 to a 3.90 would be a noticable difference.

If I was looking to "edge" the cars performance upwards without the big changes, this would be as far as I would go for a truly good dual purpose car.
Engine mods mods (cam timing/size) would be mild. As well as a converter to match the cam.
It is still possible to run pretty fast with 3.55's. It'll just take a lot of torque. Often known as a bigger engine or supercharger. LOL!

 

[wilsonlar1]

What torque converter do you have? A switch from a stock converter to a good performance converter will improve acceleration more than a switch from 3.23s to 3.55s. But yeah, you need a sure-grip in there.

Not sure what torque converter I have. I haven't gotten inside to see what's in there.

 

[Ron H]

I did this change on my '63 Poly and have more regret than like. Yeah it's snappier off the line; but sucks on the freeway at 65-70mph. If you have a bigger motor I think this change makes perfect sense. My motor and trans are in rebuild now so might have some better results with some adjustments being made...

 

[oldbee]

Have to remember that everyone's ears are tuned to O/D gearing with todays cars.LOL

 

[Ron H]

You're correct...this is in da plan; have to chat more with the folks doing this being a pushbutton tranny...my knowledge base on this is shallow...

 

[aldal]

Not sure of your tire diameter but here are some comparisons using 29" diameter. Good luck

Using Transmission Gear Ratio: 1.1 gives these RPM data:
Engine Speed (RPM) MPH 3.23 Gear MPH 3.55 Gear MPH 3.73 Gear
8000 RPM 194.26 MPH 176.75 MPH 168.22 MPH
7500 RPM 182.12 MPH 165.70 MPH 157.70 MPH
7000 RPM 169.98 MPH 154.65 MPH 147.19 MPH
6500 RPM 157.83 MPH 143.61 MPH 136.68 MPH
6000 RPM 145.69 MPH 132.56 MPH 126.16 MPH
5500 RPM 133.55 MPH 121.51 MPH 115.65 MPH
5000 RPM 121.41 MPH 110.47 MPH 105.14 MPH
4500 RPM 109.27 MPH 99.42 MPH 94.62 MPH
4000 RPM 97.13 MPH 88.37 MPH 84.11 MPH
3500 RPM 84.99 MPH 77.33 MPH 73.60 MPH
3000 RPM 72.85 MPH 66.28 MPH 63.08 MPH
2500 RPM 60.71 MPH 55.23 MPH 52.57 MPH
2000 RPM 48.56 MPH 44.19 MPH 42.05 MPH
1500 RPM 36.42 MPH 33.14 MPH 31.54 MPH
1000 RPM 24.28 MPH 22.09 MPH 21.03 MPH