74 Duster 408 Daily Drivability with 3.73 Gears Vs Stock 3.21 Question.

[2xabody]

Guy that installed the 3.73's lives in a good sized town with the main drag minutes away. I live in a very small town a highway runs thru so I'm a good 15 minutes from a good sized town. With the 3.73's I'm really turning the R's down the highway. I've had 3.55's in other cars and they also seem to tach a bit high. I was really worrying about take off also, clutch chatter possibilities etc... going back to the 3.21's. I don't plan to drag race it so trying to tame it down some with the stroker still in the car. I will need to take a look at cam size.

Tires can change everything

 

[273]

Tires can change everything

2-3" is like moving a step in gear ratio.

 

[65 Cuda 340]

Going from 26 inch tall tires to 28 will give you a new effective gear ratio that is 26/28 of the old one. I.e., 26/28 times 3.73 gives you 3.46. 25/29 times 3.73 equals 3.34.

 

[jbc426]

Trying to go back to as close to stock as you can? I am going to have to quit following this thread.

Sorry, but I just don't need that kind of negativity in my life.

 

[crazydog]

Here is a great calculator for comparing changes to gearing/transmissions/tire sizes in a nice side by side view.

Gear Ratio Calculator

 

[AJ/FormS]

The original 4-speed should have the T/A ratios. namely; 2.47-1.77-1.34-1.00.
This is a close ratio unit, sooooo you gotta watch your rpm Second gear is not too low.
With 3.23s and 27" tires, yur gunna get about 14mph per 1000 rpm so
2000rpm =28mph, and 32mph=2290.
If yur planning on installing a stock lo-compression 360 in front of that, the Wallace calculator predicts that factory 360 will have pressure near 133psi@730ft elevation, and feel about like a 318Magnum..... below about 3000rpm.
It's a good thing yur not looking for performance.
But, at that pressure, and geared at 65=2600 (3.23s); yur also not gunna get much for fuel-economy; even after you fix the cruise-timing.

If yur looking for max fuel economy, that factory 360 needs to be pumped up to near 200 psi, which cannot be run with iron heads and pumpgas. But can, with alloy heads. This will take about 10.8 Scr with the factory cam. and it will be a killer street-engine..........
Except for the rather modest factory cam, that's about what I run.

Be advised tho, that with 3.23s and a 2.47 first gear, the starter gear is just 7.98, and about the slowest you will be able to drive, without slipping the clutch, will be about 6mph@600rpm.... no Parading for you.

A better combo for you, might be the A833overdrive and say with 3.73s.
The ratios are 3.09-1.67-1.00-.73od.
With 3.73s the starter gear is 11.52 for 550rpm=3.8mph, now yur talking!and
65mph= 2200, which with a stock type cam is very cruisable, and you can almost give it max cruise timing. By 70/75 you'd be in.
As for second , 1.67 x 3.73= 6.23 and 32mph will be ~2480, and your 10.8 360 would easily motor away with that gear.

BTW-1
1.67 x 3.73=6.23 is the same Second Roadgear as as the standard Second gear, 1.92 x 3.23=6.24, so yur right in the Ballpark there.
BTW-2
I ran a combo like that, with 3.55s, with a 270/276/110 cam for several years. I liked it ok but when the cam dropped lobes, I went for the next bigger one. Bad idea, I've been waiting for this cam to die, since ~2005.

HappyHotRodding

 

[273]

The original 4-speed should have the T/A ratios. namely; 2.47-1.77-1.34-1.00.
This is a close ratio unit, sooooo you gotta watch your rpm Second gear is not too low.
With 3.23s and 27" tires, yur gunna get about 14mph per 1000 rpm so
2000rpm =28mph, and 32mph=2290.
If yur planning on installing a stock lo-compression 360 in front of that, the Wallace calculator predicts that factory 360 will have pressure near 133psi@730ft elevation, and feel about like a 318Magnum..... below about 3000rpm.
It's a good thing yur not looking for performance.
But, at that pressure, and geared at 65=2600 (3.23s); yur also not gunna get much for fuel-economy; even after you fix the cruise-timing.

If yur looking for max fuel economy, that factory 360 needs to be pumped up to near 200 psi, which cannot be run with iron heads and pumpgas. But can, with alloy heads. This will take about 10.8 Scr with the factory cam. and it will be a killer street-engine..........
Except for the rather modest factory cam, that's about what I run.

Be advised tho, that with 3.23s and a 2.47 first gear, the starter gear is just 7.98, and about the slowest you will be able to drive, without slipping the clutch, will be about 6mph@600rpm.... no Parading for you.

A better combo for you, might be the A833overdrive and say with 3.73s.
The ratios are 3.09-1.67-1.00-.73od.
With 3.73s the starter gear is 11.52 for 550rpm=3.8mph, now yur talking!and
65mph= 2200, which with a stock type cam is very cruisable, and you can almost give it max cruise timing. By 70/75 you'd be in.
As for second , 1.67 x 3.73= 6.23 and 32mph will be ~2480, and your 10.8 360 would easily motor away with that gear.

BTW-1
1.67 x 3.73=6.23 is the same Second Roadgear as as the standard Second gear, 1.92 x 3.23=6.24, so yur right in the Ballpark there.
BTW-2
I ran a combo like that, with 3.55s, with a 270/276/110 cam for several years. I liked it ok but when the cam dropped lobes, I went for the next bigger one. Bad idea, I've been waiting for this cam to die, since ~2005.

HappyHotRodding

The OP has 408

 

[TimS]

Trying to go back to as close to stock as you can? I am going to have to quit following this thread.

Sorry, but I just don't need that kind of negativity in my life.

Yes. My ultimate interest is going back to the original drivetrain and most likely sell the 408. To each his own. All thru my darn near 50 years of restoring Mopars, my enjoyment is centered around original cars. I still want to drive the Duster while I'm working on the #'s 360.

 

[jbc426]

Yes. My ultimate interest is going back to the original drivetrain and most likely sell the 408. To each his own. All thru my darn near 50 years of restoring Mopars, my enjoyment is centered around original cars. I still want to drive the Duster while I'm working on the #'s 360.

I was just teasing, and I'm actually glad there are those restoring these gems to original.

I'm pretty sure my ongoing quest for higher performance, comfort and convenience is some kind of a syndrome or disorder I caught when I rode in the back of what is my now my first car at 10 years old. I remember being pinned to the back seat while accelerating onto the highway and looking at the texture on the vinyl on the seat-back.

FWIW: My preferred style is stock appearing inside and out with bigger back tires and the enhanced sound modified motors produce, and under the hood is open for creative interpretation.

 

[Demonracer]

For an around town driver, I'd go with the 3.55 gear. It has decent street manners and stop light to stop light can be fun. For a dual purpose highway/street, or mostly highway, I'd go with the 3.23 gear. I've run many different ratios on the street and I pretty much always go with the 3.23 or 3.55 depending on where I'm going to be driving.

 

[michiganpat]

I considered it.

A lot more involved and its an expensive venture.

GV only offers one option for A-Body's and requires mods.

Buy Now - Gearvendors

could look at an iron case A833 OD. my duster has one with 3.23's and I love love love it. gears are a bit wide spaced (3.09/1.67/1/.73) but cruising 70 mph at 2100 RPM is wonderful, and with a moderate cam (thinking 224-230@.050), a 408 should have no problem with the gear spacing and running at that RPM in 4th..

 

[TimS]

For an around town driver, I'd go with the 3.55 gear. It has decent street manners and stop light to stop light can be fun. For a dual purpose highway/street, or mostly highway, I'd go with the 3.23 gear. I've run many different ratios on the street and I pretty much always go with the 3.23 or 3.55 depending on where I'm going to be driving.

I fall under the highway/street, mostly highway scenerio and why I'm going back to the original 3.21SG and removing the 3.73SG in the 8 1/4.

 

[jbc426]

I fall under the highway/street, mostly highway scenerio and why I'm going back to the original 3.21SG and removing the 3.73SG in the 8 1/4.

Match that gearing change with a high-quality torque converter, and never look back.

 

[65 Cuda 340]

Match that gearing change with a high-quality torque converter, and never look back.

View attachment 1716475250

His trans is a 4 speed.

Good looking Barracuda convertible. Roll bar?