carrman
Senior Member
Thank you sir, ignore the PM I just sent asking your opinion....;-)
A question of rear ends.
- Thread starter carrman
- Start date
yes the 2.76 and 3.23 comparison above is what I have noticed. I have no need for a 2.76. Doesn’t matter how much power, better wit a 2.94 or 3.23
They have 3 different size yokes, and they can come on anything regardless of the housing number.
They have 3 different size yokes, and they can come on anything regardless of the housing number.
carrman
Senior Member
Guess I won't know what yoke to get until I get the case thats going to be built and get my car on a lift to see what u-joint it has now.
I had my gears changed on my 73 Imperial from 2.76 to 3.91. Huge difference, however it was too much. The car isn’t pleasant to be driven on highways anym. I’m planning to go back to 3.23 or 3.55. Whatever you pick keep in mind to get an assembled rear end or go deep in research for the gear brand. An experienced mechanic changed the gears twice and I still have whining at 40 mph.
Gerald Morris
Senior Member
For the city, a 3.23 seems ideal. If I cruised the highway, I'd want a 2.94 or 2.76 even. My fuel economy was marginally better with the 2.XY rear end we ran on Mathilda, and I might deploy it short term again, while rebuilding the 3.23 I now run on Gertrude. IFF we do that job, I'll set some Sure Grip system up. I like the modern stuff I see at Dr. Diff.: Mopar 8 3/4" (8.75) Clutch Type Sure-Grip ("Powr-lok") If one is to rebuild the rear end nowadaze, I reckon this is the way to go.
RemCharger
Active Member
Possibly from a long haired passenger?
I've had that before.
SF_James
New Member
I need to make a decision in the next week on gear ratios for a 1964 Chrysler 300K.
Now this car is taking over the daily driving duties, we do not own a "modern" car, from our 1947 Desoto Suburban after 20 years. The wife wants power steering and AC in retirement.
The car has 742 factory 3.23, no power loc. I have a spare 742 with 2.76.
On paper, using the 1959 dyno runs of a 413 and looking at the fuel use at highway RPM in a theoretical 3000 mile coast to coast trip the car would use about 140 more gallons with a 3.23 than a 2.76.
I have noted however in this thread that the people who tried it have noticed that the car bogs down so much that they have to hit the throttle hard to accelerate and the like thus negating the paper improvement in mileage.
I would appreciate any comments from more folks that have played mix and match and the real world differences in fuel use. A lot of cross country traveling with current fuel prices makes this more than an intellectual exercise.
Of course we could buy a new car, but we like traveling in truly American Made Cars.
Thanks for the thoughts. James
Now this car is taking over the daily driving duties, we do not own a "modern" car, from our 1947 Desoto Suburban after 20 years. The wife wants power steering and AC in retirement.
The car has 742 factory 3.23, no power loc. I have a spare 742 with 2.76.
On paper, using the 1959 dyno runs of a 413 and looking at the fuel use at highway RPM in a theoretical 3000 mile coast to coast trip the car would use about 140 more gallons with a 3.23 than a 2.76.
I have noted however in this thread that the people who tried it have noticed that the car bogs down so much that they have to hit the throttle hard to accelerate and the like thus negating the paper improvement in mileage.
I would appreciate any comments from more folks that have played mix and match and the real world differences in fuel use. A lot of cross country traveling with current fuel prices makes this more than an intellectual exercise.
Of course we could buy a new car, but we like traveling in truly American Made Cars.
Thanks for the thoughts. James
Personally the 3.23 is perfect With 15” tires, 2.76 is too much in the wrong direction. I like the 2.94 if you want to lower freeway rpm but still have some torque.
Rear end gears are about torque multiplication. And the 2.76 gears kill the torque. what car need torque? Trailer towing. What was the gear ratio on a Chrysler corp trailer tow package? 3.23
Rear end gears are about torque multiplication. And the 2.76 gears kill the torque. what car need torque? Trailer towing. What was the gear ratio on a Chrysler corp trailer tow package? 3.23
SF_James
New Member
Thank you. I do recognize what you are saying. What i am trying to find out is from people who have tried multiple gears on the same car is what is a good, if such a thing exists, between torque and gas mileage for daily driver - cross country car.
We need to know how fast you drive, how much weight is in the car and the height of your rear tires, it all makes a difference.
I’ve done it and had all the ratios from 2.76 to 3.91.
I go with the 2.94 for cross country driving. the 2.76 actually made the gas mileage go down in a 383. Turned it into a dog.
SF_James
New Member
A 1964 300K is about 4400 pounds. I have 14 inch wheels on it with tires at 26.6. That said, I will be going to 15 inch wheels and tires would be 27.6.
Just Carbs
Well-Known Member
I have 64 413 New Yorker stock rear gear. Two tire sets, 205/75-14 and 235/75-15 tires.
Yes, the little tires are better at 0-to-30-part throttle in traffic. But the big tires are not in any way power deficient.
The car is lovely at 80 mph with the big tires.
I run the big tires. Just longer in first gear.
That's not going to change without a cam change.
Yes, the little tires are better at 0-to-30-part throttle in traffic. But the big tires are not in any way power deficient.
The car is lovely at 80 mph with the big tires.
I run the big tires. Just longer in first gear.
That's not going to change without a cam change.
SF_James
New Member
What is your gear ratio? James
Just Carbs
Well-Known Member
It is in fact a 2.76.
I would like more pull at full throttle with a 3.23 from 20 to 45 in first gear. Very happy otherwise. So, no gear change.
If I were to change anything it would be to change everything. Cam, 3.55 gear, exhaust, more intake, more carb, timing curve.
And spin it to 6k.
I would like more pull at full throttle with a 3.23 from 20 to 45 in first gear. Very happy otherwise. So, no gear change.
If I were to change anything it would be to change everything. Cam, 3.55 gear, exhaust, more intake, more carb, timing curve.
And spin it to 6k.
57fury440
Well-Known Member
I think with 2:76 gears and 27.6" tires you are going to feel like the car is stuck in molasses on take-off. I don't think it would be a good combination for towing. I understand that you want the best miles per gallon for long trips, but you still want the car to drive nicely.
SF_James
New Member
I do not plan on towing anything. What concerns me is that a couple of people who have dropped from 3.23 have found that they tend to have to lean into the throttle more and that tends to negate the better mileage from the numerically lower gears.
So what I am fishing for are first hand accounts from folks with full size cars and otherwise stock 360 HP or close big blocks.
James
Towing aside, I wouldn't want to be driving a big V8 that's doing 2K or more on the highway at 60 MPH. These big engines are supposed to have enough torque to not need to spool up to high RPM's just to drive 60+ on the highway. I think my '01 Ram (RWD) with 318 (and overdrive) is doing 1800 at 65 mph.
Just Carbs
Well-Known Member
I didn't see any mpg difference between the 14 and 15 tires in traffic. The 15 is 2 mpg better at 70. The 14 was less fun at 80.
The 15 has plenty of part throttle for all driving. I don't tow with it.
64 413 340 horse.
Owen11x
Well-Known Member
I have a B body with a 340 and 3.23 gears in a 8.75... It's an ok gear. Good cruising gear. I have a C body with 3.55gear and 8.75 rear with a hot little 318 definitely better and I have a 71 duster with a hot 340 and 4 speed. That's a mint combo that is a blast. But 3.55 is the best town and highway gear of any of my rides hands down. 3.91 is the most fun but also my only 4 speed car until I get the next duster done.
Dads300
Active Member
If your big block is stock and tuned correctly, it should pull 2.76 gears with relative ease. I have had 2.76 gears in stock 318 A and B body cars that had no issues with interstate speeds and mountains. I currently have a 71 d100 with stock 318, 2.76, 30” tires, and weighs 4500 lbs. That truck has terrible aero, but will haul the mail on the interstate all day long at 80 mph+. These experiences are over the last 30 years in the western US where speeds are high and the grades are long. I can’t believe an RB powered c body in good tune wouldn’t yield the same results.
Travis..
Travis..
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