Gear Ratos/RPM's

UglyFast88 · 06-14-2002, 10:25 AM

Does anyone have RPM specs for the different gear ratios from 3.08 to 4.10?

I need to pick a new setup, and I've got 3.08's right now (I think, the tag is gone) and want to get something that I can still drive on the highway, but want to see where they would be at 75MPH...

I'm thinking 3.73's, but I just want to be sure.

Thanx,
Joe

kdog · 06-18-2002, 03:55 PM

Here's a formula I got out of a magazine a few years back, but you have to know your transmission's final drive ratio:

MPH*TRANS RATIO*AXLE RATIO*336
DIVIDED BY TIRE DIAMETER

PKRWUD · 06-18-2002, 04:18 PM

I have a similar formula that I use. What is the diameter of your tires?

Take care,
-Chris

Oldschoolpony · 06-18-2002, 05:21 PM

Right here on this site is software to help you. Just click on "analyzer" to the left in the site map tab. It will tell you exactly what you want to know.

fiveohpatrol · 06-19-2002, 01:49 AM

I have 3.73's and about 26" tall tires (275/50 15's) and in overdrive with a T-5 at 80mph its about 2500-2600rpm on an autometer tach.

I'd say 75mph is about 2300-2400rpm or so.

hope this helps some, later,
-Drew

RPM427 · 06-19-2002, 01:00 PM

If you are using your stock tach then the estimates will be off a little. After you see a stock tach working next to an good aftermarket one, you will be amazed at the difference in accuracy.

06-14-2002, 10:25 AM	#1
UglyFast88 Registered Member Join Date: Apr 2002 Location: Fordland Posts: 117	Gear Ratos/RPM's Does anyone have RPM specs for the different gear ratios from 3.08 to 4.10? I need to pick a new setup, and I've got 3.08's right now (I think, the tag is gone) and want to get something that I can still drive on the highway, but want to see where they would be at 75MPH... I'm thinking 3.73's, but I just want to be sure. Thanx, Joe __________________ '88 Speed Density LX 1998 Explorer motor 1.7 Roller Rockers GT-40 lower ported & polished Cobra upper intake MAC CAI Aluminum Pullies FRPP P-Shortys Cop car cam (to insult) Competition Engineering F/R adjustables Flowmasters New black carpet and... '84 Racin' Tempo seats! Cars' best run in 2002 with stock 150,000 mile 302 with pullies, exhaust and roller rockers only... 13.27 at 101.5 mph

06-18-2002, 04:18 PM	#3
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	I have a similar formula that I use. What is the diameter of your tires? Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

06-18-2002, 05:21 PM	#4
Oldschoolpony Registered Member Join Date: Mar 2001 Location: Gainsville,Fl Posts: 229	right here Right here on this site is software to help you. Just click on "analyzer" to the left in the site map tab. It will tell you exactly what you want to know. __________________ http://www.mustangworks.com/cgi-bin/...splay.cgi?1546

06-19-2002, 01:49 AM	#5
fiveohpatrol I'd rather be basketweaving Join Date: Feb 2000 Location: Indianapolis Posts: 2,551	I have 3.73's and about 26" tall tires (275/50 15's) and in overdrive with a T-5 at 80mph its about 2500-2600rpm on an autometer tach. I'd say 75mph is about 2300-2400rpm or so. hope this helps some, later, -Drew __________________ NMRA O/C 9516 NA pumpgas stickshift 347 10.65@125.6, 6.73@100, 1.41 60ft

06-19-2002, 01:00 PM	#6
RPM427 Registered Member Join Date: Aug 2001 Location: Huntington NY Posts: 573	If you are using your stock tach then the estimates will be off a little. After you see a stock tach working next to an good aftermarket one, you will be amazed at the difference in accuracy. __________________ -1993 Mustang, 900rwhp 03-04 cobra based 4v swap, full Griggs setup, project underway -1994 Ranger w/ 427cid windsor (daily beater) check it out!

06-18-2002, 03:55 PM	#2
kdog Registered Member Join Date: May 2000 Location: Abilene, TX Posts: 70	Here's a formula I got out of a magazine a few years back, but you have to know your transmission's final drive ratio: MPHTRANS RATIOAXLE RATIO*336 DIVIDED BY TIRE DIAMETER

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