Question about gear ratios??? HELP
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From: Way up in the mountains
Question about gear ratios??? HELP
I am planning on putting a 3.54 ratio ring and pinion in my Dana 60 (in a '77 F250). Can anyone give me an estimate of speed and rpm's runnin 235/85/16's? I believe those tires are 31 inches tall but I could be wrong. 4th gear is 1 to 1 ratio I know that....I just want to know what my speed and rpms should be. I travel a lot of interstate so basically I would like the estimates from 50 miles an hour to 85 miles an hour(I live in Montana =)) so speed and rpm's with the new gearing would be great.
Also, if there is anybody who has done this (switched to 3.54 from 4.10) is there a lot of noticable change in regards to speed/rpm ratio? I am hoping this will allow me to go faster and save a little gas. Looking for any info I can get. Thanks a lot.
Also, if there is anybody who has done this (switched to 3.54 from 4.10) is there a lot of noticable change in regards to speed/rpm ratio? I am hoping this will allow me to go faster and save a little gas. Looking for any info I can get. Thanks a lot.
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From: Houston/Hope BC
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Not intending to hijack, but I used the link to calculate my ratio -
NP 435 Trans, should be 1:1
3:50-1 gears
31 in. tire diameter
At 65, my tach reads around 3500 rpm. The calculator says it should be 2500. I wonder what the deal is?
(I have tested the speedo - at 60 mph, I do average 1 mile per min based on highway mile markers)
NP 435 Trans, should be 1:1
3:50-1 gears
31 in. tire diameter
At 65, my tach reads around 3500 rpm. The calculator says it should be 2500. I wonder what the deal is?
(I have tested the speedo - at 60 mph, I do average 1 mile per min based on highway mile markers)
Last edited by 79 posi; Jul 23, 2005 at 10:55 PM.
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From: Not this forum
Originally Posted by Awsum77
I am planning on putting a 3.54 ratio ring and pinion in my Dana 60 (in a '77 F250). Can anyone give me an estimate of speed and rpm's runnin 235/85/16's? I believe those tires are 31 inches tall but I could be wrong. 4th gear is 1 to 1 ratio I know that....I just want to know what my speed and rpms should be. I travel a lot of interstate so basically I would like the estimates from 50 miles an hour to 85 miles an hour(I live in Montana =)) so speed and rpm's with the new gearing would be great.
Also, if there is anybody who has done this (switched to 3.54 from 4.10) is there a lot of noticable change in regards to speed/rpm ratio? I am hoping this will allow me to go faster and save a little gas. Looking for any info I can get. Thanks a lot.
Also, if there is anybody who has done this (switched to 3.54 from 4.10) is there a lot of noticable change in regards to speed/rpm ratio? I am hoping this will allow me to go faster and save a little gas. Looking for any info I can get. Thanks a lot.
Last edited by 3 of 7; Jul 23, 2005 at 11:12 PM.
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From: Way up in the mountains
wow. everybody is getting different results. Well right now i run about 3000 at 60mph and I have been told by so many people that cant be true but i have tested my speed runnning along 3 of my friends cars and its very very close. I just want to be able to go faster with out my engine screamin. Like i said I live in Montana and everyone here goes around 80 on the interstate and its amazing how many hand gestures I have gotten. I travel back and forth to school alot and I just want to go faster. When I first got the truck I didnt have a tach in but I took it up to 75 and ever since then I have not gone over 60. I have 2 inch dual exhaust with cherry bombs and at around 65 i can hear my motor over my exhaust and i know thats not good. That aside, will I be able to go faster with less strain on my engine?
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From: Not this forum
Originally Posted by Awsum77
wow. everybody is getting different results. Well right now i run about 3000 at 60mph and I have been told by so many people that cant be true but i have tested my speed runnning along 3 of my friends cars and its very very close. I just want to be able to go faster with out my engine screamin. Like i said I live in Montana and everyone here goes around 80 on the interstate and its amazing how many hand gestures I have gotten. I travel back and forth to school alot and I just want to go faster. When I first got the truck I didnt have a tach in but I took it up to 75 and ever since then I have not gone over 60. I have 2 inch dual exhaust with cherry bombs and at around 65 i can hear my motor over my exhaust and i know thats not good. That aside, will I be able to go faster with less strain on my engine?
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From: Houston/Hope BC
I checked the calculator manually and the math is right so Mr. 69 Posi something is amiss in your inputs. A little error here and there adds up to a big error in the solution.
(Tire diameter is the worst and hardest to measure.)
Awsum: cross multiply will solve your question (no tires to measure)
60 mph X 4.10 = 69 MPH X 3.54 (RPM same 3000)
(Tire diameter is the worst and hardest to measure.)
Awsum: cross multiply will solve your question (no tires to measure)
60 mph X 4.10 = 69 MPH X 3.54 (RPM same 3000)
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I wonder if my tach is simply screwed up?
In order to be off close to 1000 rpm, I would have to have 22" tire diameter. That is the only input that could be variable unless my gears were swapped out (I will have to check that out next time I get a chance). Even then, if I estimated the tires to only be 30" tall, the gear ratio would have to be around 5.25:1 in order to be around 3500 rpm.
In order to be off close to 1000 rpm, I would have to have 22" tire diameter. That is the only input that could be variable unless my gears were swapped out (I will have to check that out next time I get a chance). Even then, if I estimated the tires to only be 30" tall, the gear ratio would have to be around 5.25:1 in order to be around 3500 rpm.
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From: Not this forum
Originally Posted by Ecuri
(Tire diameter is the worst and hardest to measure.)
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From: Colorado
Ratios, RPM, and speed have always confused me....a few weeks back some friends and i were cruising to a car show...one of my friends was in his 31 coupe, one in his 53 pickup, and me in my 53 car....at 80 MPH we were all between 3900 and 4200 rpm, all cars with different tire sizes, different gear ratios, and different motors/trannies...
I have 4.10's in my truck, and was running a 28" or so tire, i just put 33" tires on it...i know i will have a lower RPM for a higher MPH now...but does anyone know the math equation to figure out "how much rpm the taller tire adds" I know theres calculators online to figure it out, but being able to go thru an equation is ALOT more fun and impressive...
--JB
I have 4.10's in my truck, and was running a 28" or so tire, i just put 33" tires on it...i know i will have a lower RPM for a higher MPH now...but does anyone know the math equation to figure out "how much rpm the taller tire adds" I know theres calculators online to figure it out, but being able to go thru an equation is ALOT more fun and impressive...
--JB
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From: Not this forum
Originally Posted by 79 posi
I may be smoking crack here, but isn't tire diameter simply the tire height? Not the distance around?
What do you use the tire circumference for?
What do you use the tire circumference for?
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From: Houston/Hope BC
Yes, diameter(D) = height (theoretically)(and stay away from that!)
circumference(C) = Pi (3.14159...)x D
D x Tire Revolutions=Distance traveled in one minute in inches
So the formula is, so you can have lots of fun :
Speed (MPH) = Engine RPM/Trans Gear Ratio/Final Drive Ratio x (C)in x 60min/5280ft x 12in
There will be a test on Tuesday, and yes, you will have to show your work.
circumference(C) = Pi (3.14159...)x D
D x Tire Revolutions=Distance traveled in one minute in inches
So the formula is, so you can have lots of fun :
Speed (MPH) = Engine RPM/Trans Gear Ratio/Final Drive Ratio x (C)in x 60min/5280ft x 12in
There will be a test on Tuesday, and yes, you will have to show your work.