2.76 vs 2.94 gearing

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1968 Dart 270

1968 Dart 270

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Hi,how much difference (if any) would I see in performance and mileage switching from a 7 1/4" with 2.94 rear to one with 2.76 gears? This is in a 68 dart with 273 and torqueflite . Not doing this because I want to,but because there's something wrong with the original rear end. Anybody who's experienced both I'd be interested in hearing your opinions. This is obviously not a hot rod,just a daily driver being driven as Chrysler intended jt to be. I'm thinking the difference would be negligible,but I've been happy with the 2.94 gears
 
Those are cruiser gears. By going that direction you will be save a few hundred RPM when your at cruse vs what you currently have. But to me the cost is not worth it. If you want a little bit more pep out of the car and don’t care about gas MPG I would go the other direction and go to 3.23.

This and others will help explain.

 
It shouldn't be too big of a difference, maybe a little less acceleration but slightly better highway/cruise rpm. I changed my Demon from 3.91 to 2.94 for a road trip. Now that was a BIG difference. Cruise was amazing. Here is a link to Wallace Racing Calculators. Calculate GEAR, RPM, MPH, TIRE DIAMETER

Looking at 26" tire, 1:1 trans ratio, 2.94 gear and 60mph (5% slip figured in for converter) - 2395 rpm
Looking at 26" tire, 1:1 trans ratio, 2.76 gear and 60mph (5% slip figured in for converter) - 2247 rpm
 
The difference will be bigger than you think. You will be in each gear longer before shifting, will hurt acceleration and mileage. I run 2.94 in many cars, but the 2.76 in small engine hurts the drivability and fuel mileage.

Tell us about you and your car, what's been done to the engine for more power? How do you drive it? Freeway, around town, any hills or is it flat there. What size rear tires are on it?

Remember riding a 10 speed bike. Starting out in 8-10th gear is hard to get it moving compared to 2nd gear. Same power & weight, same machine, different gearing

I bought a 4000lb car with a 440+6, 2500 converter amd 2.76. It was not good from a stop, rpm high and working engine to get it going. Then changed to 3.23 and it drives out easily and converter doesn't flash up so high to move the car.
 
The difference?
Slightly less acceleration and slightly more mileage.
That’s it. If you cruise the car, you’ll like the 2.76 better.

I had that ratio, the 2.76, in my ‘79 Magnum w/a 360/904 on 26” tires and I was able to get up to 20 mpg’s. No headers, dual exhaust off of the exhaust manifolds @ 2-1/4 inch. The car was pretty loaded. A/C, PS, PB, electric windows, etc….
 
This is not that complicated, just do the 2:76. May have to change your speedo gear. OP says he has a problem with his current rear end , he's going to change it.
I have 2:76's in my Dart, it's a driver, not a hot rod, it will get around just fine.
 
413 said:
The difference will be bigger than you think. You will be in each gear longer before shifting, will hurt acceleration and mileage. I run 2.94 in many cars, but the 2.76 in small engine hurts the drivability and fuel mileage.

Tell us about you and your car, what's been done to the engine for more power? How do you drive it? Freeway, around town, any hills or is it flat there. What size rear tires are on it?

Remember riding a 10 speed bike. Starting out in 8-10th gear is hard to get it moving compared to 2nd gear. Same power & weight, same machine, different gearing

I bought a 4000lb car with a 440+6, 2500 converter amd 2.76. It was not good from a stop, rpm high and working engine to get it going. Then changed to 3.23 and it drives out easily and converter doesn't flash up so high to move the car.
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It's an entirely stock 68 dart with 273 2bbl and torqueflite. It's a daily driver. I drive it like Ward Cleaver not Mario Andretti. LOL. I do city and freeway driving.
 
1968 Dart 270 said:
It's an entirely stock 68 dart with 273 2bbl and torqueflite. It's a daily driver. I drive it like Ward Cleaver not Mario Andretti. LOL. I do city and freeway driving.
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It will be fine, they made many with 2.76. You will need to change speedo gear for it to be accurate.

You will notice it drives different. If you have any hills you will notice them
If you pass on a 2 lane highway it will be more of a dog thatn before.
 
play around with the speed calculator.. Speed/Tire/RPM calculator


26" tires

2.76 @ 3000 RPM = about 84 MPH
2.94 @ 3000 RPM = about 78 MPH

for my 4000 mile trip i'm gonna try to put a 2.76 in our dart. once finished the trip i'm going 2.94. love the 2.94 gears..





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I like the 2.94 gears too. That's why I was curious as to how dramatic the difference would be.
 
I have just put a 2.94 gear set in my 68 dart convertible with the 225 slant six. I just had 2.76's in it last summer. Now I also changed some ignition stuff and only had the car out once so far due to all this rain. But on high ways and hills (which is what I drive to work) I really didnt "feel" any major difference when it came to performance. No idea about fuel mileage, but I am sure it would be similar enough that I dont care about the change.
 
You'll lose 7% in torque multiplication, basically like losing around 20 lbs-ft across the board at the crank.
 
carfreak6970 said:
I have just put a 2.94 gear set in my 68 dart convertible with the 225 slant six. I just had 2.76's in it last summer. Now I also changed some ignition stuff and only had the car out once so far due to all this rain. But on high ways and hills (which is what I drive to work) I really didnt "feel" any major difference when it came to performance. No idea about fuel mileage, but I am sure it would be similar enough that I dont care about the change.
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That's kind of what I was assuming but wasnt sure.some of the replies made it sound like the difference would be more dramatic. I'd like to find 2.94's but the 2.76 rear is what's near and available so far.
 
1968 Dart 270 said:
I like the 2.94 gears too. That's why I was curious as to how dramatic the difference would be.
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If you had the town you live in listed instead of USA, someone close to you may have something to help you. When I see a member looking for a part and their location is close to mine, I try to help out.
I may have a 2.94 axle but it is in a '76 model car with the bigger bolt pattern.
 
I went from 2.93 to 3.23 there was a slight improvement in 1/4 mile.

But regular driving I do not notice any difference.

Rear end swap is pretty straight forward and easy so go for the 2.76 and if you end up not liking it there are always 7.25s that come up for free or 100.00 bucks.

Or save up to do an 8-3/4 swap.
 
1968 Dart 270 said:
That's kind of what I was assuming but wasnt sure.some of the replies made it sound like the difference would be more dramatic. I'd like to find 2.94's but the 2.76 rear is what's near and available so far.
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I imagine you 273 powerband is fairly flat, so even with less rpm per mph you'll have similar hp available to you at the same general road speeds.
 
something about forests and trees...

with 273 2bbl backed by a 904 with 7.25 in a dart as a daily grocery getter, the answer is half a gnats ***. or practically nothing.

swap it and roll till it pukes its guts out, rinse and repeat.
 
People, it's more than freeway RPM, it is torque multiplication, and a 273 doesn't have much to spare.

2.76 gears killed a 383-2bbl for me.

Remember your 10 speed bike?
 
Are we still talking about a 6.2% change in ratio? It is 9% going from his currently bad 2.94 to 3.23 but he doesn't have those. Run it
 
Thanks for all the input guys. Like 71GssDemon said,iI'm Just going to go for it and keep looking for an 8 3/4" eventually.
 
Kern Dog said:
If you had the town you live in listed instead of USA, someone close to you may have something to help you. When I see a member looking for a part and their location is close to mine, I try to help out.
I may have a 2.94 axle but it is in a '76 model car with the bigger bolt pattern.
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too bad you're in CA, as I'd be all over that for my duster since I just did a factory disc conversion on my drum car and need to change the rear bolt pattern on my car, but I'm in west Michigan.
 
The 7 1/4" big bolt rear axle is great for that.
AS long as you're not hammering the throttle, the 7 1/4" axle lasts and lasts. A few things that kill them is sudden shock loads like peeling out on a loose surface then onto pavement. The rotational movement suddenly slows way down when you gain traction and all that momentum can blow out the differential. Manual transmission and 7 1/4" axles are not a good combination if you're making any power.
 
Your car will be super slow, and you will have your foot down on the pedal getting it to move of the line I wouldn’t run 2.76 unless you were driving highway only.
 
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