How Would I Know What Gearing Is In My Stang

5.0_H.O · October 10th, 2006, 09:17 AM

I Have An 87 Gt, I was Wonder If Anyone Would Roughly Know What Gearing Is In My Car. It Revs At Around 1800 RPM around 60MPH

ChrisJ · October 10th, 2006, 09:22 AM

Get your car up on a lift...

Mark the drive shaft and the tire with chalk...

Count how many times the driveshaft goes around for every one round of the tire...

That is the easiest way IMHO...

If the driveshaft turns 2 3/4 times for every one turn of the tire you have 2.73 or so...

If the driveshaft turns 3 times then you prolly have 3.08's...

Drivshaft turns 3 1/2 times for every turn of the tire then you prolly have 3.55's...

Driveshaft turns 3 3/4 times then you have 3.73's...

If the the driveshaft turns 4 times then you prolly have 4.10's...

Hope this helps...

88BlueGT · October 10th, 2006, 11:19 AM

+1 Thats definetly the easiest way. But from your RPM's it sounds like you might have 3.08's or 3.27's in your car. In my 93 with 2.73's, I am at about 1800 at 70 mph... or close to it; that may not be exact.

ChrisJ · October 10th, 2006, 11:37 AM

I forgot to put the 3.27 in there lol...

If your drive shaft turns 3 1/4 time then you prolly have 3.27's...

Tony_90fox · October 10th, 2006, 03:11 PM

how far off will my speedometer be when i put my 4:10s in? the gears are stock right now, i dont know what they are in a 90 LX 5.0 auto, but i wanted to know if i have to get a new speedo cable or not? Thanks

Jojogunne · October 10th, 2006, 09:46 PM

I couldn't find what size gear is inside your trany 6,7, or 8 ( which you need to know ) but here is good article on speedo gears and rear sizes

http://www.ffcobra.com/FAQ/speedo.html

jjg

5.0_H.O · October 11th, 2006, 12:25 PM

I'm Thinking Of Putting 3.73 Gears In, How Much Will The Speedo Be Out And How Do I Adjust It Propertly

dr.gonzo · October 11th, 2006, 01:07 PM

I have 3.73 gears in my car. I have to divide what the spedo says by 2 so 120mph im really only going 60. makes a cool video tho...I can get upto 140 in about 6 sec.

Jojogunne · October 12th, 2006, 08:23 AM

If you have an 87 GT with the orginal T5 in it, inside driving the speedo gear you have a 7 tooth gear. With 3.73 in it you would need a 21 tooth gear. Unless you had taller profile tires. The website in my first post ( above ) has a applet that calculates all those things. Just enter you tire size and speedo gear inside the trany and it will tell you what you need.

I have an 84 with a trany out of 92 which has an 8 tooth gear in it. So when I changed my rear dif I have to keep that in mind.

jjg

Jojogunne · October 12th, 2006, 07:02 PM

how far off will my speedometer be when i put my 4:10s in? the gears are stock right now, i dont know what they are in a 90 LX 5.0 auto, but i wanted to know if i have to get a new speedo cable or not? Thanks

Your 90 auto has an 8 tooth gear driving the speedo gear. If you put 4.10's in you would need a 23 tooth speedo gear. No new cable just a new speedo gear.

jjg

Tony_90fox · October 12th, 2006, 07:42 PM

cool thanks for that info!

October 10th, 2006, 09:17 AM	#1
5.0_H.O Newbie Join Date: Oct 2006 Posts: 20	How Would I Know What Gearing Is In My Stang I Have An 87 Gt, I was Wonder If Anyone Would Roughly Know What Gearing Is In My Car. It Revs At Around 1800 RPM around 60MPH __________________ !987 Mustang Gt (Summer Car) - Ford Racing Headers, Flowmaster American Thunder Exhaust Without Cats, Flowmaster Hushpower 2 Mufflers, March Performace Ram Air Kit And Pullies, BBK Short Throw Shifter. 1997 Ford Taurus SHO (Winter Car)

October 10th, 2006, 09:22 AM	#2
ChrisJ Hmmm... 2002 Mustang GT SLOW Join Date: Jun 2006 Location: Shepherdsville, Kentucky Posts: 15,783	Get your car up on a lift... Mark the drive shaft and the tire with chalk... Count how many times the driveshaft goes around for every one round of the tire... That is the easiest way IMHO... If the driveshaft turns 2 3/4 times for every one turn of the tire you have 2.73 or so... If the driveshaft turns 3 times then you prolly have 3.08's... Drivshaft turns 3 1/2 times for every turn of the tire then you prolly have 3.55's... Driveshaft turns 3 3/4 times then you have 3.73's... If the the driveshaft turns 4 times then you prolly have 4.10's... Hope this helps... __________________ My Junk www.myspace.com/cjobe

October 10th, 2006, 11:19 AM	#3
88BlueGT Regular Join Date: Sep 2006 Location: Hamilton, NJ Posts: 202	+1 Thats definetly the easiest way. But from your RPM's it sounds like you might have 3.08's or 3.27's in your car. In my 93 with 2.73's, I am at about 1800 at 70 mph... or close to it; that may not be exact. __________________ http://i25.photobucket.com/albums/c5...8bluegt6wk.jpg 93 GT - Full Exhaust, 3.90's, Front Tubular Suspension, etc. 88 GT "Big Blue" - Body work & primer!

October 10th, 2006, 11:37 AM	#4
ChrisJ Hmmm... 2002 Mustang GT SLOW Join Date: Jun 2006 Location: Shepherdsville, Kentucky Posts: 15,783	I forgot to put the 3.27 in there lol... If your drive shaft turns 3 1/4 time then you prolly have 3.27's... __________________ My Junk www.myspace.com/cjobe

October 10th, 2006, 03:11 PM	#5
Tony_90fox MM Fanatic Join Date: Jun 2006 Location: Bowling Green, KY Posts: 3,593	how far off will my speedometer be when i put my 4:10s in? the gears are stock right now, i dont know what they are in a 90 LX 5.0 auto, but i wanted to know if i have to get a new speedo cable or not? Thanks __________________ 393 dropping in a foxbody near you, very very soon Military Crew E-3 Combat Engineer

October 10th, 2006, 09:46 PM	#6
Jojogunne Regular 1984 GT 13.79@98.99 Join Date: Sep 2006 Location: Bloomsburg PA Posts: 91	I couldn't find what size gear is inside your trany 6,7, or 8 ( which you need to know ) but here is good article on speedo gears and rear sizes http://www.ffcobra.com/FAQ/speedo.html jjg __________________ Eibach Sportsline, Mac, Moroso,Comp Cams,PRW roller rockers, and no money left over.

October 11th, 2006, 12:25 PM	#7
5.0_H.O Newbie Join Date: Oct 2006 Posts: 20	I'm Thinking Of Putting 3.73 Gears In, How Much Will The Speedo Be Out And How Do I Adjust It Propertly __________________ !987 Mustang Gt (Summer Car) - Ford Racing Headers, Flowmaster American Thunder Exhaust Without Cats, Flowmaster Hushpower 2 Mufflers, March Performace Ram Air Kit And Pullies, BBK Short Throw Shifter. 1997 Ford Taurus SHO (Winter Car)

October 11th, 2006, 01:07 PM	#8
dr.gonzo Enthusiast Join Date: Oct 2006 Location: kc mo Posts: 790	I have 3.73 gears in my car. I have to divide what the spedo says by 2 so 120mph im really only going 60. makes a cool video tho...I can get upto 140 in about 6 sec.

October 12th, 2006, 08:23 AM	#9
Jojogunne Regular 1984 GT 13.79@98.99 Join Date: Sep 2006 Location: Bloomsburg PA Posts: 91	If you have an 87 GT with the orginal T5 in it, inside driving the speedo gear you have a 7 tooth gear. With 3.73 in it you would need a 21 tooth gear. Unless you had taller profile tires. The website in my first post ( above ) has a applet that calculates all those things. Just enter you tire size and speedo gear inside the trany and it will tell you what you need. I have an 84 with a trany out of 92 which has an 8 tooth gear in it. So when I changed my rear dif I have to keep that in mind. jjg __________________ Eibach Sportsline, Mac, Moroso,Comp Cams,PRW roller rockers, and no money left over.

October 12th, 2006, 07:42 PM	#11
Tony_90fox MM Fanatic Join Date: Jun 2006 Location: Bowling Green, KY Posts: 3,593	cool thanks for that info! __________________ 393 dropping in a foxbody near you, very very soon Military Crew E-3 Combat Engineer

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