2:91 or 3:55?

-
I ran 3.55’s with 26” tall rear tires in my Duster when I had the 833. I run around on the freeway a decent amount and they still worked ok, 75mph was like around 3,600 rpm. Not crazy, not something I’d want to run for 6 hours either. But it worked ok.
 
a friend installed 2.94's in his stock lo compression 74 360 duster along with a 904 modified with the later transmission lo first and second gears.
said it had tremendous low end and cruised smooth on the highway with no noise or high rev harmonics.
 
In my cars, I like a 2.94 or a 3.23 with 14" tires & a 3.55 with 15" tires.
 
my68barracuda said:
spends about 75% of it's time under 55mph with 1-2 times a month at 75-80 for a few hours.

without getting into some serious tire swapping, the effect of the gear change on the vehicles pull away will come down to a gut decision.
However you can simulate the engine noise / car feel with the gear options. Use one of the online gear ratio / rpm calculators to determine the engine rpm at say 55 mph and at 75 to 80 mph with your existing tire size. Then perhaps using a lower gear in the transmission hit that engine rpm in highway conditions for each gear set. You won't be doing the actual MPH that you listed, but the engine will be spinning like it was, so you can get a feel for it.
Click to expand...
I agree on your Siri but there's also the wind noise as well to take into consideration? As the speed picks up and that a body flying Brick of hours can start a pretty good disturbance as we get going above certain speeds? Just food for discussion...
 
my68barracuda said:
spends about 75% of it's time under 55mph with 1-2 times a month at 75-80 for a few hours.

without getting into some serious tire swapping, the effect of the gear change on the vehicles pull away will come down to a gut decision.
However you can simulate the engine noise / car feel with the gear options. Use one of the online gear ratio / rpm calculators to determine the engine rpm at say 55 mph and at 75 to 80 mph with your existing tire size. Then perhaps using a lower gear in the transmission hit that engine rpm in highway conditions for each gear set. You won't be doing the actual MPH that you listed, but the engine will be spinning like it was, so you can get a feel for it.
Click to expand...

Yep, did that and it turns out to be about 2,800 at 75mph in OD and I can totally handle that.
Thank you for the input on it.
The 3:55 gears are already part way done. (tore it all down and changed the ring over)
Went to a buddies house today and pressed in the new 2" wheel studs to compensate for the discs on the original A body axles.
I just need the large end M802048 cone, M802011 cup and the 2881041 pinion seal.
I have everything else including a crush sleeve eliminator kit with shim selection.
 
ir3333 said:
a friend installed 2.94's in his stock lo compression 74 360 duster along with a 904 modified with the later transmission lo first and second gears.
said it had tremendous low end and cruised smooth on the highway with no noise or high rev harmonics.
Click to expand...
lol... exact same drive train as my '76 Duster, except my tranny is stock. Low end torque is not a problem, and it cruises so nice at 60 mph going to the dragway.
 
No one else has said it yet so I’ll go ahead and play devil’s advocate. If you got an overdrive, find some 4.56’s and drive something else for the high speed stuff.
 
I used to think 3.55s were ideal . But with todays high speed interstates I find myself running 3800 rpms just to keep up with traffic !
I installed a set of 2.76s for a roadtrip and have yet to take them out. Now its a pooch on acceleration.
I wanna OD !
 
Add a 2nd identical car that way no one would know the difference but you :rofl:
 
Seriously, though. What transmission are you using, what’s your rear tire size and what engine mods do you have. The closer to stock you are with a 1:1 final drive, the best gear for what you describe is 3.23:1.
 
Garrett Ellison said:
Seriously, though. What transmission are you using, what’s your rear tire size and what engine mods do you have. The closer to stock you are with a 1:1 final drive, the best gear for what you describe is 3.23:1.
Click to expand...

5.9 Magnum with EQ heads/1.92 intakes, Oregon cam grinders 214/224, 1 5/8 long tubes, Edelbrock dual plane, Edelbrock 600 electric, HEI ignition and distributor advance mods.

Trans is a 42RH overdrive with converter lockup, 2:73 rear gears and 245/40 18 Nitto Extreme performance tires at 25 inches tall.
Soon to be 8.25 Sure Grip 3:55 geared disc brake rear end.

It's obviously a top end car right now that I did a lot of interstate driving with, but in the process of making it more of an around towns car now.
I can put up with the higher R's on the freeways and have it quicker in the here and there average driving stuff purely for the fun of it.

show.jpg
 
That sounds like a happy build combination, that’s a very slick looking car! With the .69:1 overdrive and lockup, 3.55s, no question. That’s equivalent to 2.45s in overdrive, which will have you 2000 rpm at 60 and at 2600 rpm cruise (right were the torque is starting to really happen) at 80 accounting for tire growth at that speed. Happy Motoring! The 2.74:1 low will probably be a challenge for traction, but the 1.54 second will give enough rpm drop to help recover and get things rolling.
 
Last edited:
mbaird said:
@TrailBeast
Is that the original color ?
Looks awesome !
Click to expand...

Thanks guys.
That is basically the original color, but repainted


Garrett Ellison said:
That sounds like a happy build combination, that’s a very slick looking car! With the .69:1 overdrive and lockup, 3.55s, no question. That’s equivalent to 2.45s in overdrive, which will have you 2000 rpm at 60 and at 2600 rpm cruise (right were the torque is starting to really happen) at 80 accounting for tire growth at that speed. Happy Motoring! The 2.74:1 low will probably be a challenge for traction, but the 1.54 second will give enough rpm drop to help recover and get things rolling.
Click to expand...

You got that right about first gear, as it will probably hit second about when the rear tires hit the second line of a crosswalk.
It tries to break loose in second accelerating hard as it is.
It's been a great car and reliable as can be, and now it's time to change it up a bit.

These Nitto tires are pretty sticky, so we'll see how it does.
It should leave the line in a hurry.
 
Of course being a Swinger interior never came in white and was supposed to have a black top.
But I just could not live with black during our 100 degree summers.
And I like the White/ Red contrast !

You understand being in AZ
 
Last edited:
You must log in or register to reply here.
-

Back
Top