2.76 vs 2.94 gearing

-
Now this is my opinion.
3.21/3.23 are what I consider great balance gears, decent off the line with some highway ability.
2.76/2.93 are great freeway gears, but it will leave off some pep off the line, and as you've stated here would be good since you're just cruisin' and do a lot of freeway drivin'
Some would even consider 3.55 as great balanced gears, to some extend it is (again IMO) but at 70+ mph it'll be a bit buzzy.

I have a pretty hot 360 and I have 3.21 gears (8.25 axle). And I've done a few 500+ mile trips with it.
With 26 inch diameter tires at 3000 rpm's I go about 71-72 mph, The absolute best was a little over 17 mpg. Mostly hung between 15-16 mpg.
Now I can imagine what would happen if I had 2.76 (about a 15% reduction in RPM) going the same speed but only doing about 2500 rpm...

That being said I have a 3.55 8.75 axle I'm going to be putting in soon *sigh* I guess I am a glutton for punishment... But maybe it'll motivate me to start my OD project sooner.
 
Depending on your current power output and how you drive it you may actually get less mileage with the 2.76 gears than the 2.94 ratio because the engine will have to work harder trying to pull on those taller gears (numerically lower).

Tom
 
You said freway driving, that means 2.76. My 67 Dart 273 2bbl 2.71 gears, 225-70-15 rear tires. Get 20-21 mpg. A big help would be the A&A Transmission part throttle kickdown kit, it helps drivability a bunch.
.
 
lemondana said:
You said freway driving, that means 2.76. My 67 Dart 273 2bbl 2.71 gears, 225-70-15 rear tires. Get 20-21 mpg. A big help would be the A&A Transmission part throttle kickdown kit, it helps drivability a bunch.
.
Click to expand...
It's free to manually downshift at any time you feel it's needed.
 
1968 Dart 270 said:
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.
Click to expand...
Why? If you drive like Ward Cleaver, there's zero need for the 8.75.
 
RustyRatRod said:
Why? If you drive like Ward Cleaver, there's zero need for the 8.75.
Click to expand...
exactly! you can buy at least 10 7.25's for the price of a 8.75 and then we get to have the discussion about the difference in power between a 2.45 and a 2.76 the next time.

i see this as a win-win
 
At one time
I had every rear end chunk, pre-set and ready to go, from 2.76 to 5.38; except 3.73s, 4.56s, 5.13s..
And I had a GVod (still do). So I could run anything. and I did. with a 4-speed. Which, ties the engine directly to the road. So I notice even the half-gear changes.

With the auto, the only places I feel the difference are, at zero mph, at WOT, and of course at the Cruize-rpm.
What I discovered was that a higher stall easily made up for any power/torque loss in first gear.
So I ran a 2800 stall with 2.94s one winter, and 2.76s in another.
With the 2800, the 2.76s were fine. The difference going down from 2.94s is 6.5%, so the cruise rpm dropped from 2380@zero-slip, to 2234. not that big a difference
But, when you stomp it at 30 mph, with 2.76s, and it goes into first@2780 rpm, don't hold your breath. But hang on; 2.94s was only 2960, so I mean, what's the big deal, the 273 is choked either way, and the difference is like 6>7 horsepower.
By the way, I ran a low-compression 318 with a 4bbl/ with a 2800; and I liked the 2.76s better, lol.
 
junkyardhero said:
exactly! you can buy at least 10 7.25's for the price of a 8.75 and then we get to have the discussion about the difference in power between a 2.45 and a 2.76 the next time.

i see this as a win-win
Click to expand...
Hey,if nothing else at least some entertainment came out of my misfortune. Lol. And it's interesting to hear one person say there will be a huge difference and others say it won't matter. I drive it gently because I have read so many threads here where people claim the 7 1/4" is "as fragile as glass" and "can't even stand up to the power of a 273 or 318 driven normally". Also I see no reason to abuse and beat on a car. Why? These arent easy to find in decent shape anymore,and I see boneheads on youtube and in real life destroying and crashing their cars driving recklessly and doing burnouts in traffic. Im not a kid trying to impress anyone. Gas is also $5 a gallon out here so I don't care about having a big motor. To me the enjoyment is just driving them,not breaking and ruining them and then constantly spending thousands to fix sometning that need not have happened in the first place.but to each his own. Im mostly into the finned Chrysler products which arent about speed anyway,so im used to driving like Ward Cleaver. :) So if down the road I find a 8 3/4" reasonably priced or one in a junkyard or in cheap 4 dr then I'll swap it out for that so I won't ever have to worry about it again. I just found a 68 in a junkyard locally and got my ac vents and a ton of other parts for peanuts. (Rear end was already gone) You just have to be patient
After all the parts flippers aren't paying their asking prices for the things they are reselling either. I once got a Chrysler Highway HiFi off craiglist for $25 bucks.

These two guys are an example of more money than brains.
 
Last edited:
Rug_Trucker said:
I did a few Bonzi runs in my day Naples, to Nashville and back in the 198 Duster. 82mph with 3:23's (it came new with those) and the 3 speed manual. 22mpg.
Click to expand...
Wow! That's pretty good. I've always wondered if the feather duster really got the mileage they advertised
 
RustyRatRod said:
Why? If you drive like Ward Cleaver, there's zero need for the 8.75.
Click to expand...
The comment was meant somewhat jokingly. I just meant im not beating on the car and breaking the tires loose at every light. I drive extra gentle with the car because all I ever hear is that these 7 1/4" rears are junk and will "grenade" behind even a 273 Especially if you accelerate going into a turn. Hell,some claim they break behind a slant six. Plus isnt not in my nature to beat on classic cars or show off. Going to a 8.75 eliminates the risk of breaking the rear.
 
the 7.25 gets a bum rap for a few reasons. it was a lightweight axle to begin with, and people tend to forget these cars were built as basic disposable transportation back then. ma mopar didn't intend for these axles to last 40, 50, 60 years.

another part of it is that as people upgraded they quickly exceeded the limits of the components. from the start they weren't intended to take that much power. then you add bigger tires with more traction and now you've just pulled the pin on a grenade.

a final piece of the puzzle is that these rear ends have been in service for-ev-er. underneath bread and butter hand me down cars that every teen and 20 something (and 40 something) takes great delight in doing brake stand burnouts and half a block long one wheel peels.

is it any wonder that they break after that much abuse? you have something that's far exceeded its intended application in use, time and power level-- and been doing so well past the whole "best by date".

to me, 7.25 is just a stop gap. sure you can go get another one for $10 and a burrito. and then one afternoon you're making a right and dip your 205/70-14 into some water at the curb, goose it a little to get in front of the on coming bus and she sizzles just a little, hits the dry pavement and suddenly it sounds like two robots ******* in a dumpster and all the toofs of them gears is in the bottom of the housing and you're back in the same boat again.
 
1968 Dart 270 said:
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
Click to expand...
I have experience with the opposite. My '79 Aspen wagon had 2.71 gears and I needed the axle rebuilt and couldn't tie the car up while it was being done. So I popped a 2.94 in it while the rebuilt was being done. I lost about 2-3mpg in fuel economy and saw a very slight increase in off the line acceleration - with a A999 deep gear set T/F and a lockup torque converter. So, you need to decide what your priorities are. My focus is my wallet. The less I spend to run the car, the better I like it. 27.5mpg on the highway is better than 24.
 
Just so you know;
Back in about 74 I installed a 340 into a 65 Valiant wagon that had been home to a slanty.
I used an A904 that I unbolted from a 273.
I left the 7.25 in the back. Hey nobody told me they were weak. I was 22ish at the time, maybe 21.
Only the short block was 340.
The entire top end was 318, including the cam and induction.
I installed some Hooker Fenderwell headers, the easiest way to hook that up.
To say that the 340 was a torque-monster would not do it justice.
I drove that car for three summers I think, peg-leging the ever-loving crap out of that baby.
And then the trans blew up.
I took the powertrain out, and gave the car to my little brother, who put the slanty back in, and drove it for several more years.
I still have that engine and trans. The car went AWOL, a long ago time ago. The brother is dead.

The point is that the 7.25, in my case at least, was NOT made of glass.
 
1968 Dart 270 said:
Hey,if nothing else at least some entertainment came out of my misfortune. Lol. And it's interesting to hear one person say there will be a huge difference and others say it won't matter. I drive it gently because I have read so many threads here where people claim the 7 1/4" is "as fragile as glass" and "can't even stand up to the power of a 273 or 318 driven normally". Also I see no reason to abuse and beat on a car. Why? These arent easy to find in decent shape anymore,and I see boneheads on youtube and in real life destroying and crashing their cars driving recklessly and doing burnouts in traffic. Im not a kid trying to impress anyone. Gas is also $5 a gallon out here so I don't care about having a big motor. To me the enjoyment is just driving them,not breaking and ruining them and then constantly spending thousands to fix sometning that need not have happened in the first place.but to each his own. Im mostly into the finned Chrysler products which arent about speed anyway,so im used to driving like Ward Cleaver. :) So if down the road I find a 8 3/4" reasonably priced or one in a junkyard or in cheap 4 dr then I'll swap it out for that so I won't ever have to worry about it again. I just found a 68 in a junkyard locally and got my ac vents and a ton of other parts for peanuts. (Rear end was already gone) You just have to be patient
After all the parts flippers aren't paying their asking prices for the things they are reselling either. I once got a Chrysler Highway HiFi off craiglist for $25 bucks.

These two guys are an example of more money than brains.
Click to expand...

The one person (or people) who say there'll be a big difference are simply wrong.
 
1968 Dart 270 said:
The comment was meant somewhat jokingly. I just meant im not beating on the car and breaking the tires loose at every light. I drive extra gentle with the car because all I ever hear is that these 7 1/4" rears are junk and will "grenade" behind even a 273 Especially if you accelerate going into a turn. Hell,some claim they break behind a slant six. Plus isnt not in my nature to beat on classic cars or show off. Going to a 8.75 eliminates the risk of breaking the rear.
Click to expand...
Go for it.
 
AJ/FormS said:
Just so you know;
Back in about 74 I installed a 340 into a 65 Valiant wagon that had been home to a slanty.
I used an A904 that I unbolted from a 273.
I left the 7.25 in the back. Hey nobody told me they were weak. I was 22ish at the time, maybe 21.
Only the short block was 340.
The entire top end was 318, including the cam and induction.
I installed some Hooker Fenderwell headers, the easiest way to hook that up.
To say that the 340 was a torque-monster would not do it justice.
I drove that car for three summers I think, peg-leging the ever-loving crap out of that baby.
And then the trans blew up.
I took the powertrain out, and gave the car to my little brother, who put the slanty back in, and drove it for several more years.
I still have that engine and trans. The car went AWOL, a long ago time ago. The brother is dead.

The point is that the 7.25, in my case at least, was NOT made of glass.
Click to expand...
at the time, how many miles were on that 10 year old rear end? and what size were the tires?
 
I don't know how strong they are, I've had the 7 1/4" spider gears go a few times behind slant 6's but never a ring and pinion and or axles go.
 
1968 Dart 270 said:
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
Click to expand...
I have a 2.94 geared open diff complete 7.25 out of a 67 Dart in Ohio I'd sell to you. PM me if interested.
 
AJ/FormS said:
Just so you know;
Back in about 74 I installed a 340 into a 65 Valiant wagon that had been home to a slanty.
I used an A904 that I unbolted from a 273.
I left the 7.25 in the back. Hey nobody told me they were weak. I was 22ish at the time, maybe 21.
Only the short block was 340.
The entire top end was 318, including the cam and induction.
I installed some Hooker Fenderwell headers, the easiest way to hook that up.
To say that the 340 was a torque-monster would not do it justice.
I drove that car for three summers I think, peg-leging the ever-loving crap out of that baby.
And then the trans blew up.
I took the powertrain out, and gave the car to my little brother, who put the slanty back in, and drove it for several more years.
I still have that engine and trans. The car went AWOL, a long ago time ago. The brother is dead.

The point is that the 7.25, in my case at least, was NOT made of glass.
Click to expand...
It's refreshing to hear something positive about the 7 1/4". Wish mine had held up like that,but I don't know.how it was driven before I bought it. Hope the next one holds up like yours did.
 
RustyRatRod said:
For 2 bucks, no less!
Click to expand...
Yep,that's what Junkyardhero and others were saying. Nobody wants them and you can usually get them for super cheap or free. Too bad that ones in Ohio. $2 bucks is even cheaper than this one. That's a price even Jack Benny can't grouse about! Lol.
 
My 7/14 lasted 323,000 miles behind a 273 2bbl and 904.

It would still be in use today but it was run dry (leak or not refilled at last lube change) for up to 20,000 miles.
 
Last edited:
You must log in or register to reply here.
-

Back
Top