Re: Help me pick a gear ratio....
[Re: mercman1]
#991393
05/13/11 01:24 AM
05/13/11 01:24 AM
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Joined: Oct 2003
Posts: 3,698 NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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What tire you runnin?
I agree with the 3.73 if using 28s. Taller tire=3.91s-4.10.
If you have it set on kill, 4.10s all the way.
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Help me pick a gear ratio....
[Re: Kern Dog]
#991394
05/13/11 01:32 AM
05/13/11 01:32 AM
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Joined: Jul 2008
Posts: 30,486 Florida STAYcation
dOc …
The village idiot's idiot
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The village idiot's idiot
Joined: Jul 2008
Posts: 30,486
Florida STAYcation
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F-berri ..... THINK about it this-way. As many miles as you put on your car ... how many of those miles benefit from that stiff gear ? MILES ? ... how about measuring it in FEET !! I have a car that is lighter than yours ...a 62 Belevedere with lotsA' fiberglass ...and have a 2.76 gear in it and I LOVE IT. SURE the car doesn't gate that hard(1.82 vs 1.65) .... but with a shorter gear ... those "100-roll" shots are fun ..... And you will love that MPG.
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Re: Help me pick a gear ratio....
[Re: Kern Dog]
#991396
05/13/11 06:00 AM
05/13/11 06:00 AM
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Joined: Jan 2003
Posts: 5,907 Athens, Greece
Pyper70
master
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master
Joined: Jan 2003
Posts: 5,907
Athens, Greece
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If you leave the 3.23's in there and you put the GVO unit you will be driving with a 2.43 (around there) in final gear. You'll get great gas mileage but I fear you wont the engine rpms will be super low on the freeway at that speed. I have 3.55s with a 28" tire...at 80mph with the GVO engaged I am doing about 2600rpm...without I am doing about 3500. With the 3.55s my final ratio is 2.76
Family owned 1969 Charger R/T DualQuad 440/727/GVO/3.55s
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Re: Help me pick a gear ratio....
[Re: The_Mean_Machine]
#991399
05/13/11 08:12 AM
05/13/11 08:12 AM
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Joined: Oct 2003
Posts: 21,345 Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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I guess I don't mind RPM... with an OD trans set-up, I'd look at going back to the 3.90-4.10 range with shorter car tires. my Dakota has a 3.92 gear set, 28.5" tires, and it only spins around 2500 rpm down the freeway. (OD is only around .75)
my TKO big block set up had a 4.56 rear gear for awesome off the line pull, yet with the .64 OD 5th gear, it was also only doing about 2500 rpm at highway speeds.
I had a 3.23 set up with that high of an OD, and was "idling" at 1800 rpm down the freeway, and with the cam I have, I was lugging the engine and it was NOT smooth to drive till I got up around 75MPH
Hey, Doc, I know you keep bragging about your 12 sec car that gets great MPGs with 2.76 gears. have you ever considered that half the argument is in all the glass parts on the car? your car weighs significantly LESS than the average A-body.
I think weight has more to do with MPGs than engine size or gear ratio. I'll go back to the Dakota's to illustrate this-- a 3.9L dakota gets 16-18 MPGs. a 5.9L dakota gets 15-17 MPGs. why do 2 engines, WAY different in size, get similar MPGs? what's the same? vehicle weight and aero. the hp needed to move 4,000 lbs through the air is the same regardless of the engine size, and to generate that Hp, you have to burn X lbs of fuel/hr. doesn't matter if you're burning it in 6 cylinders or 8...it's the same total amount.
**Photobucket sucks**
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Re: Help me pick a gear ratio....
[Re: 70Cuda383]
#991402
05/13/11 09:29 AM
05/13/11 09:29 AM
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Joined: Jul 2008
Posts: 30,486 Florida STAYcation
dOc …
The village idiot's idiot
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The village idiot's idiot
Joined: Jul 2008
Posts: 30,486
Florida STAYcation
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Quote:
Hey, Doc, I know you keep bragging about your 12 sec car that gets great MPGs with 2.76 gears. have you ever considered that half the argument is in all the glass parts on the car? your car weighs significantly LESS than the average A-body.
I think weight has more to do with MPGs than engine size or gear ratio. I'll go back to the Dakota's to illustrate this-- a 3.9L dakota gets 16-18 MPGs. a 5.9L dakota gets 15-17 MPGs. why do 2 engines, WAY different in size, get similar MPGs? what's the same? vehicle weight and aero. the hp needed to move 4,000 lbs through the air is the same regardless of the engine size, and to generate that Hp, you have to burn X lbs of fuel/hr. doesn't matter if you're burning it in 6 cylinders or 8...it's the same total amount.
Hay Tom .... then lighter weight sure helps in the ET dept ... but not-much-at-all for fuel econ. ... and the AERO of a 62
PLUS the motor is a bit down on power.
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Re: Help me pick a gear ratio....
[Re: patrick]
#991403
05/13/11 09:33 AM
05/13/11 09:33 AM
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Joined: Jul 2008
Posts: 30,486 Florida STAYcation
dOc …
The village idiot's idiot
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The village idiot's idiot
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Florida STAYcation
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Quote:
TALLER GEAR....numerically lower gears are TALLER/HIGHER, numerically higher gears are SHORTER/LOWER
by your logic, "low gear" in your tranny would be 3rd (1:1) not 1st (2.45:1 for a 727)
Hey patrick ...I am talking about REAR END gears. Now if you can't accept that ...... BITE ME !
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Re: Help me pick a gear ratio....
[Re: cogen80]
#991407
05/14/11 11:58 AM
05/14/11 11:58 AM
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Joined: Apr 2010
Posts: 1,216 Under My Car
Mopar_Country
pro stock
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pro stock
Joined: Apr 2010
Posts: 1,216
Under My Car
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Quote:
Quote:
Eventually I intend to install a Gear Vendors unit.
3.55. then with a gv it should b around a 2.76. best of both worlds.
3.55's, I'm quite happy with them in my car, I went from a 2.76 open to 3.55 suregrip. Although I don't have the size car nor the power you have. Instead of a cam swap why not throw a suregrip in there instead, just a thought.
You might try one of the online calculators and play with the numbers a little, write down the different combo's that you try as you go.
http://www.ramblerman.com/blazer/gearcalc.htm
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Re: Help me pick a gear ratio....
[Re: 70Cuda383]
#991408
05/16/11 10:12 AM
05/16/11 10:12 AM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
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Grand Haven, MI
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Quote:
Quote:
Another consideration is the 3000 rpm stall speed of the converter. I know that this car can never be a fuel sipper, but I wonder if I need to target a freeway rpm somewhere near the stall speed to avoid cooking the trans? The 3.23 set spins the motor (Or the other way around) at about 2600 at 65. Maybe the "final drive" with the GV should be near 3.23. With this in mind, the GV has an OD ratio od .78. The 4.10 X .78 is 3.20 while the 3.91 X .78 is 3.05. What are your thoughts on cruising UNDER the converter stall speed? It seems that the motor might act a little lazy and inefficient.
my understanding is that a GOOD converter, it won't matter. it'll only slip when you're giving it lots of torque. so part throttle cruise down the highway and it won't slip much.
a good high stall converter won't slip significantly more below the stall speed than above. stall speed is the RPM of max torque multiplication. a "tight" high stall converter with tall gears is a good compromise, especially if you have a torquey motor.
I had 3.55's with 27" tall tires and HATED it, buzzing along at ~3300 RPM at 75moh on the freeway got old after about 20 minutes. I put an A500 in and kept the 3.55's. if I didn't have the option of an OD tranny, I wouldn't go more than 3.23's, possibly even 2.94's, depending on tire size.
and Doc Fiberglass, yes I was talking about rear gears, too.
TALLER (higher) gears are NUMERICALLY LOWER RATIOS (2.2:1, 2.76:1, etc)--2.76 turns of the driveshaft = 1 turn of the axle
SHORTER (lower) gears are NUMERICALLY HIGHER RATIOS (3.91:1, 4.10:1, etc) 4.1 turns of the driveshaft = 1 turn of the axle.
you might have come up with your own definitions, but sorry, this is just how the rest of the world defines them. if you don't believe me, just google "tall vs. short gearing" and see what you come up with.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: Help me pick a gear ratio....
[Re: patrick]
#991409
05/16/11 10:20 AM
05/16/11 10:20 AM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Quote:
Quote:
Another consideration is the 3000 rpm stall speed of the converter. I know that this car can never be a fuel sipper, but I wonder if I need to target a freeway rpm somewhere near the stall speed to avoid cooking the trans? The 3.23 set spins the motor (Or the other way around) at about 2600 at 65. Maybe the "final drive" with the GV should be near 3.23. With this in mind, the GV has an OD ratio od .78. The 4.10 X .78 is 3.20 while the 3.91 X .78 is 3.05. What are your thoughts on cruising UNDER the converter stall speed? It seems that the motor might act a little lazy and inefficient.
my understanding is that a GOOD converter, it won't matter. it'll only slip when you're giving it lots of torque. so part throttle cruise down the highway and it won't slip much.
a good high stall converter won't slip significantly more below the stall speed than above. stall speed is the RPM of max torque multiplication. a "tight" high stall converter with tall gears is a good compromise, especially if you have a torquey motor. Pete, who works at XV (I think his moparts handle is GmachinedartGT) has a killer combo running a tight, high stall converter behind a 408 and 2.94's...highway cruising is comfortable, and it'll still crank out low 12's in the 1/4....
I had 3.55's with 27" tall tires and HATED it, buzzing along at ~3300 RPM at 75moh on the freeway got old after about 20 minutes. I put an A500 in and kept the 3.55's. if I didn't have the option of an OD tranny, I wouldn't go more than 3.23's, possibly even 2.94's, depending on tire size.
and Doc Fiberglass, yes I was talking about rear gears, too.
TALLER (higher) gears are NUMERICALLY LOWER RATIOS (2.2:1, 2.76:1, etc)--2.76 turns of the driveshaft = 1 turn of the axle
SHORTER (lower) gears are NUMERICALLY HIGHER RATIOS (3.91:1, 4.10:1, etc) 4.1 turns of the driveshaft = 1 turn of the axle.
you might have come up with your own definitions, but sorry, this is just how the rest of the world defines them. if you don't believe me, just google "tall vs. short gearing" and see what you come up with.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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