How To: Calculate RPM for your Gear Ratio

NoKturnaL · 02-07-2005, 04:14 PM

For those of you who WONDER what RPM's you will be at, at a certain miles per hour, in a curtain gear here is a great tool! this will help me in my decision on what gear I should get.
www.tchracing.com/tech/gearcalc

WaterDR · 02-07-2005, 04:17 PM

Good find! I have seen those things before...this one seems easy to use. We should move this to the "How To" Section.

281!!! · 02-07-2005, 04:23 PM

what trans do i pick for a 99 auto???

NoKturnaL · 02-07-2005, 04:27 PM

OK..now I am confused!
I was jotting in some numbers to determine what miles per hour I am going while in a curtain gear at a curtain RPM.

First I put in that I was at 5000 RPM in 3rd gear WITH the stock 3.27..and It calculated that I would be going 88MPH's.

Then I put in all the SAME numbers..only with 3.73 gears and it said I would only be going 77MPH's

Then I again put in all the same number as that But with 4.10 Gears And I was going slower at 70MPH's..

now......does that mean the stock 3.27 is the better gear???? cause I am going faster at curtain miles per hour's with 3.27 rather than the 3.73 and 4.10's...

WHats going on here?
SHOULDNT I BE GOING FASTER WITH THE 3.73 OR 4.10's???????? or is the forrmula all messed up????

WaterDR · 02-07-2005, 04:49 PM

That's right. For 4.10's you will be going at higher rpms at the same speed that you did when you had 3.27's. Or, in other words, at the same rpms, you will be traveling slower with 4.10's than with 3.27's.

Did you ever have a ten speed? Think of the rear gear sproket as your transmission, and the front sproket as just like chaging gear ratios. You will have to pedal faster with the 4.10's. make sense?

4.10's are like a tourque multiplier. They don't make the car go faster, just accelerate faster. In theory, you actually loose top speed with them.

WaterDR · 02-07-2005, 04:51 PM

Moving to "How To's"

NoKturnaL · 02-07-2005, 04:58 PM

still does not make sense for me.

If Im at 3000 RPM's and climbing with 3.27's in 2nd gear I SHOULD BE going at a slower miles per hour than with say 4.10's at 3000RPM's in 2nd gear!

AHHHHH!!! lol Let me figure this out............

NoKturnaL · 02-07-2005, 05:00 PM

ok i see. after thinking about it, I can understand. lol

MattJ · 02-07-2005, 07:59 PM

Great find!!

02wt5sp · 02-08-2005, 12:46 PM

yeah, good find! I've now decided to go with 4.10's, I'll only be at 2330.8rpms at 70, and that's not bad at all.

NoKturnaL · 02-08-2005, 07:24 PM

YEA! Isnt this an Excellent tool???!?!?!?!

I always wondered what rpms I would be doing at certain speeds! :headbang:

gtnumber2 · 02-09-2005, 07:03 AM

I`ve using this for a year now and it helped me to decide to go with 3.90s for a daily driver.

danbc21 · 03-03-2005, 09:09 AM

That’s is a great find. But I think it is a little off. It told me that with a TR 3650, 315/35/17 Tires, and stock 3.27 gears at 5500 RPM in 5th gear that I will be going 207.264 miles per hour :tongue9: . I don’t think that is right. What do you guys think? I think I am going to try that out, I’ll tell you how it goes (lol) :laughing7 .

jbodell11 · 03-06-2005, 06:15 PM

Quote:

Originally Posted by danbc21

That’s is a great find. But I think it is a little off. It told me that with a TR 3650, 315/35/17 Tires, and stock 3.27 gears at 5500 RPM in 5th gear that I will be going 207.264 miles per hour :tongue9: . I don’t think that is right. What do you guys think? I think I am going to try that out, I’ll tell you how it goes (lol) :laughing7 .

if your pulling that much in 5th gear with stock gears i would love to ride in your car

buddyabe · 04-06-2005, 06:40 PM

The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.

buddyabe · 04-06-2005, 06:43 PM

The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.If you put the car on a hoist off the ground and pulled 5500 rpms in 5th with no drag or resistance the rear tires would be spinning over 200 miles per hour

96stangGT · 05-05-2005, 06:20 PM

The higher the gear the more turns it takes to turn the wheel once
with 3.27 gear it takes 3.27 turns of the drive shaft to turn the wheel once
thats why the motor has to turn over more(RPM) with the higher gears to achieve the same speeds as the lower gears

Lamar · 05-09-2005, 09:13 PM

Nice link! thanks!!

MineralGT · 05-09-2005, 09:40 PM

Quote:

Originally Posted by gtnumber2

I`ve using this for a year now and it helped me to decide to go with 3.90s for a daily driver.

How do you like the performance change...I think I'm gonna go with 3.90's, I do about 75 miles a day on the freeway.

gtnumber2 · 05-25-2005, 07:19 AM

Quote:

Originally Posted by new2gt

How do you like the performance change...I think I'm gonna go with 3.90's, I do about 75 miles a day on the freeway.

i like them just thought it would be more of a through you back in your seat install. i would go with 4.10s. if you have a 5 speed definitly 4.10s.

02-07-2005, 04:14 PM	#1 (permalink)
NoKturnaL MustangTuning 5-oh Join Date: Dec 2004 Location: Peabody, MA Posts: 1,950	How To: Calculate RPM for your Gear Ratio For those of you who WONDER what RPM's you will be at, at a certain miles per hour, in a curtain gear here is a great tool! this will help me in my decision on what gear I should get. www.tchracing.com/tech/gearcalc __________________ 2002 Mustang GT Coupe 5-Speed Performance K&N Intake Accufab upper Intake Plenum Accufab 70mm Throttle Body Steeda Pullies SCT 4-Bank Chip Dyno Tuned Mac H-pipe Flowmaster Cat-Back Steeda Shifter Centerforce Clutch SLP-Line-Lock And more upgrades visually

02-07-2005, 04:17 PM	#2 (permalink)
WaterDR Administrator Join Date: Sep 2004 Posts: 6,363	Good find! I have seen those things before...this one seems easy to use. We should move this to the "How To" Section. __________________ Black 2000 GT Vert: Novi-2000 with Intercooler (375rwhp @ 9 psi); Tune by Kauffmans; Roush 380R Body kit; Steeda Subframes; Steeda Strut Tower Support; Deep Dish Bullets; FRPP 4:10's; SCT 4 Position Chip with four custom tunes; Steeda CAI; C&L Pleum; BBK 75 TB; SLP Loudmouth; SLP Catted X-Pipe; Bullitt Suspension; UPR Conrol Arms; Focus Fuel Pump My Car My Email

02-07-2005, 04:23 PM	#3 (permalink)
281!!! Member Join Date: Feb 2005 Location: Minnesota Posts: 50	hmmmm?? what trans do i pick for a 99 auto???

02-07-2005, 04:27 PM	#4 (permalink)
NoKturnaL MustangTuning 5-oh Join Date: Dec 2004 Location: Peabody, MA Posts: 1,950	OK..now I am confused! I was jotting in some numbers to determine what miles per hour I am going while in a curtain gear at a curtain RPM. First I put in that I was at 5000 RPM in 3rd gear WITH the stock 3.27..and It calculated that I would be going 88MPH's. Then I put in all the SAME numbers..only with 3.73 gears and it said I would only be going 77MPH's Then I again put in all the same number as that But with 4.10 Gears And I was going slower at 70MPH's.. now......does that mean the stock 3.27 is the better gear???? cause I am going faster at curtain miles per hour's with 3.27 rather than the 3.73 and 4.10's... WHats going on here? SHOULDNT I BE GOING FASTER WITH THE 3.73 OR 4.10's???????? or is the forrmula all messed up???? __________________ 2002 Mustang GT Coupe 5-Speed Performance K&N Intake Accufab upper Intake Plenum Accufab 70mm Throttle Body Steeda Pullies SCT 4-Bank Chip Dyno Tuned Mac H-pipe Flowmaster Cat-Back Steeda Shifter Centerforce Clutch SLP-Line-Lock And more upgrades visually

02-07-2005, 04:49 PM	#5 (permalink)
WaterDR Administrator Join Date: Sep 2004 Posts: 6,363	That's right. For 4.10's you will be going at higher rpms at the same speed that you did when you had 3.27's. Or, in other words, at the same rpms, you will be traveling slower with 4.10's than with 3.27's. Did you ever have a ten speed? Think of the rear gear sproket as your transmission, and the front sproket as just like chaging gear ratios. You will have to pedal faster with the 4.10's. make sense? 4.10's are like a tourque multiplier. They don't make the car go faster, just accelerate faster. In theory, you actually loose top speed with them. __________________ Black 2000 GT Vert: Novi-2000 with Intercooler (375rwhp @ 9 psi); Tune by Kauffmans; Roush 380R Body kit; Steeda Subframes; Steeda Strut Tower Support; Deep Dish Bullets; FRPP 4:10's; SCT 4 Position Chip with four custom tunes; Steeda CAI; C&L Pleum; BBK 75 TB; SLP Loudmouth; SLP Catted X-Pipe; Bullitt Suspension; UPR Conrol Arms; Focus Fuel Pump My Car My Email

02-07-2005, 04:51 PM	#6 (permalink)
WaterDR Administrator Join Date: Sep 2004 Posts: 6,363	Moving to "How To's" __________________ Black 2000 GT Vert: Novi-2000 with Intercooler (375rwhp @ 9 psi); Tune by Kauffmans; Roush 380R Body kit; Steeda Subframes; Steeda Strut Tower Support; Deep Dish Bullets; FRPP 4:10's; SCT 4 Position Chip with four custom tunes; Steeda CAI; C&L Pleum; BBK 75 TB; SLP Loudmouth; SLP Catted X-Pipe; Bullitt Suspension; UPR Conrol Arms; Focus Fuel Pump My Car My Email

02-07-2005, 04:58 PM	#7 (permalink)
NoKturnaL MustangTuning 5-oh Join Date: Dec 2004 Location: Peabody, MA Posts: 1,950	still does not make sense for me. If Im at 3000 RPM's and climbing with 3.27's in 2nd gear I SHOULD BE going at a slower miles per hour than with say 4.10's at 3000RPM's in 2nd gear! AHHHHH!!! lol Let me figure this out............ __________________ 2002 Mustang GT Coupe 5-Speed Performance K&N Intake Accufab upper Intake Plenum Accufab 70mm Throttle Body Steeda Pullies SCT 4-Bank Chip Dyno Tuned Mac H-pipe Flowmaster Cat-Back Steeda Shifter Centerforce Clutch SLP-Line-Lock And more upgrades visually

02-07-2005, 05:00 PM	#8 (permalink)
NoKturnaL MustangTuning 5-oh Join Date: Dec 2004 Location: Peabody, MA Posts: 1,950	ok i see. after thinking about it, I can understand. lol __________________ 2002 Mustang GT Coupe 5-Speed Performance K&N Intake Accufab upper Intake Plenum Accufab 70mm Throttle Body Steeda Pullies SCT 4-Bank Chip Dyno Tuned Mac H-pipe Flowmaster Cat-Back Steeda Shifter Centerforce Clutch SLP-Line-Lock And more upgrades visually

02-07-2005, 07:59 PM	#9 (permalink)
MattJ Senior Member Join Date: Dec 2004 Location: Racine, WI Posts: 10,243	Great find!! __________________ 2001 Mustang GT Premium - Mineral Grey

02-08-2005, 12:46 PM	#10 (permalink)
02wt5sp rice..it'swhat'sfordinner Join Date: Sep 2004 Location: hampton va Posts: 324	yeah, good find! I've now decided to go with 4.10's, I'll only be at 2330.8rpms at 70, and that's not bad at all. __________________ NO MORE GT!!! UPGRADED TO COBRA!!! Mods: magnaflow catback, JLT CAI bone stock dyno #'s 372rwhp and 364rwtq

02-08-2005, 07:24 PM	#11 (permalink)
NoKturnaL MustangTuning 5-oh Join Date: Dec 2004 Location: Peabody, MA Posts: 1,950	YEA! Isnt this an Excellent tool???!?!?!?! I always wondered what rpms I would be doing at certain speeds! :headbang: __________________ 2002 Mustang GT Coupe 5-Speed Performance K&N Intake Accufab upper Intake Plenum Accufab 70mm Throttle Body Steeda Pullies SCT 4-Bank Chip Dyno Tuned Mac H-pipe Flowmaster Cat-Back Steeda Shifter Centerforce Clutch SLP-Line-Lock And more upgrades visually

02-09-2005, 07:03 AM	#12 (permalink)
gtnumber2 Senior Member Join Date: Dec 2004 Posts: 289	I`ve using this for a year now and it helped me to decide to go with 3.90s for a daily driver.

03-03-2005, 09:09 AM	#13 (permalink)
danbc21 Senior Member Join Date: Dec 2004 Location: Springfield, PA Posts: 159	That’s is a great find. But I think it is a little off. It told me that with a TR 3650, 315/35/17 Tires, and stock 3.27 gears at 5500 RPM in 5th gear that I will be going 207.264 miles per hour :tongue9: . I don’t think that is right. What do you guys think? I think I am going to try that out, I’ll tell you how it goes (lol) :laughing7 . __________________ 02 Torch Red GT Coupe 5-speed -Steeda Tri-Ax -SLP Loudmouth Catback -Motive 4.10 Gears -Mach 1 Chin Spoiler -Bullitt Pedals -K&N -Black Bumper Insert -Raised Scoop Black Designation Decals -Mach 1 Mustang Grill Delete -Black Bullitt wheels

04-06-2005, 06:40 PM	#15 (permalink)
buddyabe SILVER 01 GT CONVERT AUTO Join Date: Jan 2005 Location: coon rapids mn. u.s.a. Posts: 205	The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.

04-06-2005, 06:43 PM	#16 (permalink)
buddyabe SILVER 01 GT CONVERT AUTO Join Date: Jan 2005 Location: coon rapids mn. u.s.a. Posts: 205	The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.If you put the car on a hoist off the ground and pulled 5500 rpms in 5th with no drag or resistance the rear tires would be spinning over 200 miles per hour

05-05-2005, 06:20 PM	#17 (permalink)
96stangGT Member Join Date: Mar 2005 Posts: 37	The higher the gear the more turns it takes to turn the wheel once with 3.27 gear it takes 3.27 turns of the drive shaft to turn the wheel once thats why the motor has to turn over more(RPM) with the higher gears to achieve the same speeds as the lower gears

05-09-2005, 09:13 PM	#18 (permalink)
Lamar Member Join Date: Sep 2004 Location: Quebec, Canada Posts: 49	Nice link! thanks!! __________________ '01 GT Mineral Gray 13.62 @ 103.49 miles per hour, 2.074 60ft (k&n, pullies, 3.73, cat-back)

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