3.73 speedometer gear change?

5.0PiMpin · 01-10-2002, 03:27 AM

wats up guys , i just got my 3.73 gears installed today and i wasnt as impressed as i thought i would be. first thing im driving my car home and my speedometer was reading 70 mph and i only felt like i was going 55. i called my girlfriend who was following me and asked her wat hers said and she said 55. so i jumped on the phone with the guy who installed the gears and he said that i need to go to ford and get a new gear for the speedometer. i never heard of this before and i was wondering if he is BS'in me. wat didnt impress me about the gear change was that i thought there would a grand cloud of smoke and chirping into second with the swap. i didnt no this but the car came with 3.08's alot of people told me that the stock was 2. sumthin. i also added the aluminum drive shaft. it really works in cutting down on the interior noise that i used to get. is there sumthing that i left out that i should have added with the gear swap? ne answers would be greatly apreciated.

thanks, danny

5.0PiMpin · 01-10-2002, 03:30 AM

oh yeah i forgot to ask one more thing, does the gear change affect the rpm read out like it does the speedometer or does it stay the same.

fiveohpatrol · 01-10-2002, 11:19 AM

Well you do need a new speedometer gear for the tranny. I believe it's a 21 tooth gear for 3.73's. This is because your wheels and your transmission are now turning faster after the gear swap and are therefore making your speedometer read faster. With the correct speedometer gear, it will go back to reading correctly.

Your RPM's will read higher than they were before, but this is only because they REALLY ARE higher. So your tach is still accurate, (well as accurate as a stock tach is anyway)

Get the speedometer gear (between $10-$15) and your all set

MustangDanny · 01-10-2002, 11:28 AM

Yes you do have to change the speedo gear. Unless you are comfortable driving around with the error on your dashboard.

As far as your un-impression... I think it's because like you said, you were starting off with a higher gear from the get-go (3.08). Most people's stangs are 2.73's, and a change from teh 2.73 to 3.73 is a bit more of a difference noticed (i.e. seat of the pants) than the change from 3.08 to 3.73. Maybe you shoudl have gone for the 4.10's.

5ohCOUPE · 01-10-2002, 12:14 PM

You need a 7 tooth output shaft gear and a 21 tooth cable gear. That is what i did and my speedo is right on the money.

89FHPLX · 01-11-2002, 01:14 AM

OK, guys. I need help here to. What about a 160 spedo. That came on my X-trooper mustang. I have 3.08's now. If I get the 3.73's or 3.55's what gear should go on my tranny.

thanks.

Mad Horse · 01-11-2002, 02:53 PM

As said earlier you will need the 21 tooth for the 3.73's. With the 3.55's I think you need a 23 tooth which you can only get out of magazines because Ford doesn't sell it. However, my friend had this one and it wore out all the time because the teeth are so small to get all 23 on there. He eventually went with the 21 tooth and his speed is close to accurate.

bigballer811 · 03-28-2002, 06:06 PM

I also have the speedo problem, I have 3.73's in my car and the speedo is marking higher than it really is going which from what I hear is normal untill you put in the right speedo gear....

my question is if the odometer should be affected by the 3.73 rear gears ?cause its racking up the miles fast as well.

From what I understand I need the 23 tooth (white) speedo gear for my 95 gt vert (manual) right? Will this fix both the speedo and odometer or do I need something else to fix the odometer?

One last question how hard is the speedo gear instal, I really have very little experience dealing with car stuff, but I want to learn, so if its not too hard could someone point me to where I could read on how to do the instal (or just let me know how to do it) Thanks for any replies and sorry for so many questions.

cad614 · 03-28-2002, 06:37 PM

The white 21 tooth speedo gear can be found at your local Jeep dealership. I know it sounds crazy, but this is the exact same part that you find listed in the magazines and online.

Part # J3167393
It cost me $15, was in stock, and in my car (AODE w/ 4.10s) the speedo is dead on.

PKRWUD · 03-28-2002, 06:45 PM

4.10's require the Black 22 tooth gear (and a black 6 tooth driven gear).
3.73's require the Red 21 tooth gear.
3.55's require the Black 20 tooth gear, EXCEPT for the 1993 Cobra, which requires a 23 tooth gear (Saleen Performance Parts sells them).
3.27's require the Pink 19 tooth gear.

Take care,
-Chris

5000cc · 03-29-2002, 02:41 PM

According to Promotion Powertrain gear usage chart,if you have T-5 transmission from 82-1995 with yellow 7T input shaft gear and you have 3.08 rear end axle gear ratio you will need driven cable gear with 18T
3.27 vs 19T
3.55 vs 20T
3.73 vs 21T
4.10 vs 23T

Driven cable gear color code:
16T = wine
17T = white
18T = yellow
19T = pink
20T = black
21T = red
23T = white
I just installed 4.10 gear on mine upgrade from 3.08 and boy! what an improvement on acceleration but RPM is much higher than before also but hey!,that is the price to pay for neck snapping feeling,right?

bigballer811 · 03-29-2002, 03:36 PM

when I change the speedo gear will that fix my odometer too so it wont count miles fast or am I just gonna have to live with that?

Stang39r · 03-29-2002, 04:08 PM

i believe miles are counted by the rotation of the tire and have nothing to do with gears or anything of the sort...could be wrong but i think thats the way it goes

stock89 · 03-29-2002, 07:06 PM

The odometer is run by gears from the speedo reading. When the speedo gear is changed the milage will start reading correct again. I'm trying to remember, which plug was it for the speedo gear?? He'll need to know that too....

01-10-2002, 03:27 AM	#1
5.0PiMpin Registered Member Join Date: Nov 2001 Location: Daly City CA USA baby Posts: 42	3.73 speedometer gear change? wats up guys , i just got my 3.73 gears installed today and i wasnt as impressed as i thought i would be. first thing im driving my car home and my speedometer was reading 70 mph and i only felt like i was going 55. i called my girlfriend who was following me and asked her wat hers said and she said 55. so i jumped on the phone with the guy who installed the gears and he said that i need to go to ford and get a new gear for the speedometer. i never heard of this before and i was wondering if he is BS'in me. wat didnt impress me about the gear change was that i thought there would a grand cloud of smoke and chirping into second with the swap. i didnt no this but the car came with 3.08's alot of people told me that the stock was 2. sumthin. i also added the aluminum drive shaft. it really works in cutting down on the interior noise that i used to get. is there sumthing that i left out that i should have added with the gear swap? ne answers would be greatly apreciated. thanks, danny __________________ off road h-pipe , under drive pulley's , stage one center force clutch, removed air silencer, flows, K&N, 130 Amp pain in my alternator, optima yellow top 3.73 gears aluminum drive shaft and pro5.0 shifter...

01-10-2002, 03:30 AM	#2
5.0PiMpin Registered Member Join Date: Nov 2001 Location: Daly City CA USA baby Posts: 42	oh yeah i forgot to ask one more thing, does the gear change affect the rpm read out like it does the speedometer or does it stay the same. __________________ off road h-pipe , under drive pulley's , stage one center force clutch, removed air silencer, flows, K&N, 130 Amp pain in my alternator, optima yellow top 3.73 gears aluminum drive shaft and pro5.0 shifter...

01-10-2002, 11:19 AM	#3
fiveohpatrol I'd rather be basketweaving Join Date: Feb 2000 Location: Indianapolis Posts: 2,551	Well you do need a new speedometer gear for the tranny. I believe it's a 21 tooth gear for 3.73's. This is because your wheels and your transmission are now turning faster after the gear swap and are therefore making your speedometer read faster. With the correct speedometer gear, it will go back to reading correctly. Your RPM's will read higher than they were before, but this is only because they REALLY ARE higher. So your tach is still accurate, (well as accurate as a stock tach is anyway) Get the speedometer gear (between $10-$15) and your all set __________________ NMRA O/C 9516 NA pumpgas stickshift 347 10.65@125.6, 6.73@100, 1.41 60ft

01-10-2002, 11:28 AM	#4
MustangDanny Registered Member Join Date: Nov 2001 Location: Dover, DE Posts: 70	Yes you do have to change the speedo gear. Unless you are comfortable driving around with the error on your dashboard. As far as your un-impression... I think it's because like you said, you were starting off with a higher gear from the get-go (3.08). Most people's stangs are 2.73's, and a change from teh 2.73 to 3.73 is a bit more of a difference noticed (i.e. seat of the pants) than the change from 3.08 to 3.73. Maybe you shoudl have gone for the 4.10's. __________________ -- -1991 LX 5.0 Sedan, 5 spd (new 'Z' tranny), 3.73, aluminum DS, Hedman headers, 190 LPH, MAC CAI, Flowmaster catback. (170K miles on motor) Best ET: 14.434 @ 96.04 MPH - 2.205 60' (Radials) My Notch

01-10-2002, 12:14 PM	#5
5ohCOUPE Registered Member Join Date: Sep 2001 Location: ORANGE PARK FL. USA Posts: 208	You need a 7 tooth output shaft gear and a 21 tooth cable gear. That is what i did and my speedo is right on the money. __________________ 91 LX COUPE, 3.73 gears, 2 1/2 inch H-Pipe, 1 5/8 MAC long tube headers, 73 MM C&L MAF, 70 MM MAC TB, LUNATI cam,1.7 TFS Rockers, TFS Track Heat heads, TFS Track Heat intake, T5 with PRO 5.0 shifter, Griffin aluminum radiator, Fluid Damper, SSM traction bars, 190 GPH in tank fuel pump. And more to come.

01-11-2002, 01:14 AM	#6
89FHPLX Registered Member Join Date: Aug 2000 Location: Miami, Florida Posts: 116	OK, guys. I need help here to. What about a 160 spedo. That came on my X-trooper mustang. I have 3.08's now. If I get the 3.73's or 3.55's what gear should go on my tranny. thanks. __________________ 89 Mustang Police Interceptor Cobra Upper Intake GT-40 Lower Intake Ported TFS Track Heats Heads Crane Cams 2040 Reground By Crawford Performance 1.6 Scorpion Roller Rokers FMR 65mm TB BBk Equal Lenth Shorty Headers Billit Fuel Pressure Regulator (45Lbs) Under Drive Pullies Moroso Cold Air MSD Blaster TFI Coil X-Pipe with 2 chamber Flowmaster Cobra water pump pully 34 Degree Total Timing with spout out Short Belt No Air Silencer Hurst Short Throw Shifter Taylor 8.8 Blue Wires 3.8 Taurus Electric Fan 3.08 Gears (soon 3.55's) 19# Injectors (soon 24lb) Stock mass air

01-11-2002, 02:53 PM	#7
Mad Horse Registered Member Join Date: Sep 1998 Location: Dayton, OH., United States Posts: 467	As said earlier you will need the 21 tooth for the 3.73's. With the 3.55's I think you need a 23 tooth which you can only get out of magazines because Ford doesn't sell it. However, my friend had this one and it wore out all the time because the teeth are so small to get all 23 on there. He eventually went with the 21 tooth and his speed is close to accurate. __________________ 88GT Performance Mods: 3.73 gears, T-5Z trans, King Cobra clutch, Pro 5.0, Alum. DS, WMS Xtrac subframes, DynoMax Cat-back, PS91 Coil, March alum. Pullies, Fluidyne Rad, Elec fan Cosmetic Mods: Color change interior & exterior, Cervinis Ram air hood, 16" Ponies, LX Taillights. "Nip it in the Bud"

03-28-2002, 06:06 PM	#8
bigballer811 Registered Member Join Date: Feb 2002 Posts: 14	I also have the speedo problem, I have 3.73's in my car and the speedo is marking higher than it really is going which from what I hear is normal untill you put in the right speedo gear.... my question is if the odometer should be affected by the 3.73 rear gears ?cause its racking up the miles fast as well. From what I understand I need the 23 tooth (white) speedo gear for my 95 gt vert (manual) right? Will this fix both the speedo and odometer or do I need something else to fix the odometer? One last question how hard is the speedo gear instal, I really have very little experience dealing with car stuff, but I want to learn, so if its not too hard could someone point me to where I could read on how to do the instal (or just let me know how to do it) Thanks for any replies and sorry for so many questions.

03-28-2002, 06:37 PM	#9
cad614 Senior Member Join Date: Apr 1999 Location: San Angelo, TX Posts: 377	The white 21 tooth speedo gear can be found at your local Jeep dealership. I know it sounds crazy, but this is the exact same part that you find listed in the magazines and online. Part # J3167393 It cost me $15, was in stock, and in my car (AODE w/ 4.10s) the speedo is dead on. __________________ Mike '95 GT Convertible

03-28-2002, 06:45 PM	#10
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	FYI: For T5's: 4.10's require the Black 22 tooth gear (and a black 6 tooth driven gear). 3.73's require the Red 21 tooth gear. 3.55's require the Black 20 tooth gear, EXCEPT for the 1993 Cobra, which requires a 23 tooth gear (Saleen Performance Parts sells them). 3.27's require the Pink 19 tooth gear. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

03-29-2002, 02:41 PM	#11
5000cc Registered Member Join Date: May 1999 Location: Hialeah,Fl,USA Posts: 57	correct speedometer gear According to Promotion Powertrain gear usage chart,if you have T-5 transmission from 82-1995 with yellow 7T input shaft gear and you have 3.08 rear end axle gear ratio you will need driven cable gear with 18T 3.27 vs 19T 3.55 vs 20T 3.73 vs 21T 4.10 vs 23T Driven cable gear color code: 16T = wine 17T = white 18T = yellow 19T = pink 20T = black 21T = red 23T = white I just installed 4.10 gear on mine upgrade from 3.08 and boy! what an improvement on acceleration but RPM is much higher than before also but hey!,that is the price to pay for neck snapping feeling,right? __________________ 93 Lx coupe,125 shots wet system,BBK headers,pully,ported performer intake,24 lbs,short belt,Headman x pipe,mac catback,upr blue thunder shifter,73 mm mass air,k&n panel filter,king cobra cluth, aluminum driveshaft, 4.10 gears, cobra tranny, welds 15/6 on front and 15/10 rear.

03-29-2002, 03:36 PM	#12
bigballer811 Registered Member Join Date: Feb 2002 Posts: 14	when I change the speedo gear will that fix my odometer too so it wont count miles fast or am I just gonna have to live with that?

03-29-2002, 04:08 PM	#13
Stang39r Registered Member Join Date: Feb 2002 Location: Chicago Posts: 53	i believe miles are counted by the rotation of the tire and have nothing to do with gears or anything of the sort...could be wrong but i think thats the way it goes

03-29-2002, 07:06 PM	#14
stock89 Registered Member Join Date: Oct 2001 Location: Mannheim, Germany Posts: 124	The odometer is run by gears from the speedo reading. When the speedo gear is changed the milage will start reading correct again. I'm trying to remember, which plug was it for the speedo gear?? He'll need to know that too....

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