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Topic: 3.73 speedo gear? (Read 3982 times) previous topic - next topic

3.73 speedo gear?

i have a 88 cougar with rear disc 3.73 rear end ratio and wonder what speedo gear i need. everyone says diffrently

3.73 speedo gear?

Reply #1 –
23 teeth!!!
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

3.73 speedo gear?

Reply #3 –
Go here and use the calculator to determine the tooth count.  Once you have that figured out you can buy the speedo gears from your local dealer if you are in a bind or if not you can order them all over the internet.

http://www.sccoa.com/faq/speedgr.html

I ended up having to replace the yellow 7 tooth drive gear on the output shaft of my T-5 to a black 6 tooth so I could run an 19 tooth driven gear on the speedo cable.  I kept shreading the higher count driven gear on the speedo cable.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

3.73 speedo gear?

Reply #4 –
i bought mine at a ford dealership i think i paid like 20 bucks for it. but the did everything there

3.73 speedo gear?

Reply #5 –
23 tooth, but mine is still reading about 4-5 mph high, but that is as high numerically gear you can get.  245-50-16 rear tires.
Mike

3.73 speedo gear?

Reply #6 –
on my 88 cougar how many tooth count do i got?

3.73 speedo gear?

Reply #7 –
Quote from: jamie_d5;395348
on my 88 cougar how many tooth count do i got?

What gear ratio, what transmission, and what size tires do you have?
If you know your parts, Darren's link will pan out for ya...
'98 Explorer 5.0
'20 Malibu (I know, Chevy, but, 35MPG. Let's go brandon, eh)

3.73 speedo gear?

Reply #8 –
i dont know how many drive gear teeth i have to fill out that chart

3.73 speedo gear?

Reply #9 –
Im using a black 21 tooth with 3.73 and a 225/60/16 stock tc tire size and acorrding to my gps its 4 or  5 miles slow on the speedo
[SIGPIC][/SIGPIC]:ford:87 Turbo Coupe through the floor sub frame connectors, 5.8 swap Ford racing heads Harland sharp 1.6 rockers BBK shorty swap headers 2 1/2 BBk X pipe magnaflow ler's. Megasquirt 2 with 36lbs injectors on hurricane intake with 4150 throttle body.Tremec TKO 600 Quicktime blowsheild spec stage 3 clutch. 3.73 gears and still not done

3.73 speedo gear?

Reply #10 –
Quote from: Aerocoupe;395312
Go here and use the calculator to determine the tooth count.  Once you have that figured out you can buy the speedo gears from your local dealer if you are in a bind or if not you can order them all over the internet.

http://www.sccoa.com/faq/speedgr.html

I ended up having to replace the yellow 7 tooth drive gear on the output shaft of my T-5 to a black 6 tooth so I could run an 19 tooth driven gear on the speedo cable.  I kept shreading the higher count driven gear on the speedo cable.

Darren

So Im looking to put in an 8.8 rear with 3.73s. Tire size is 225/60/15. According to your link, AOD's have 8 tooth drive gear. So I need a 22.6 tooth speedo gear, so I should get a 23 tooth speedo gear, right?

And I might upgrade rear tires to 285/40/17. That gives me a 23.2 tooth speedo gear.

Just looking for some validation here. Thanks!
-Kyle
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.

3.73 speedo gear?

Reply #11 –
Did some interweb browsing and found someone that had posed a list of common output shafts with speedo gear combos based on year with an AOD:

1983
2.73 = 8
3.08 = 8
3.42 = 7

1984
 2.73 = 8
 3.08 = 7 Ford/Merc
 3.08 = 8 Lincoln
 3.27 = 7 unless P205/75-R15 Tires (8)
 3.42 = 7 Ford/Merc
 3.42 = 8 Lincoln
 3.55 = 7
 
1985
 2.73 = 8
 3.08 = 7 Ford/Merc (unless 225/75-R14 Tires)
 3.08 = 8 Lincoln
 3.27 = 8
 3.55 = 7
 
1986
 2.73 = 8
 3.08 = 7
 3.27 = 7
 3.55 = 7

1987
 2.73 = 8
 3.08 = 7
 3.27 = 8
 3.55 = (not listed)
 
1988
 2.73 = 8
 3.08 = 7 or 8
 3.27 = 7 or 8
 3.55 = 7

Now I am not claiming any of this to be 100% accurate and I have said I am a manual trans guy as I ripped the AOD out of my car and punted it to the curb over 24 years ago. With that said if you know for sure the tooth count on your AOD output shaft then the calculator I posted has been pretty  accurate for me over the years.  You can loose a little here and there but what I have found to be one of the biggest culprits is the speedo cable itself.

The 23 tooth gears are have a slightly different pitch to them than the stock gears so they do not last very long.  Some have good luck and they last 20K or so and others they strip after a week. To find an output shaft with 7 teeth on it and go through the pain of swapping the output shafts is just miserable if you ask me.  I would go the adapter route like this over changing a perfectly good output shaft:

https://transmissioncenter.net/shop/55ra-ford-speedometer-ratio-adapter/

You will have to buy a screw on style speedo cable but they are not expensive and most shops that sell the adapters can make you a cable based on the length of the one you have already.

You are thinking "Holy shiznit, $200 just to get my speedo to read correctly" and the answer is yes if you are going to run deep gears and an AOD.  My T-5 has a 6 tooth drive gear on it so I can run a 19 tooth driven gear with my 3.73's.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

3.73 speedo gear?

Reply #12 –
Your 86 has an electronic speedometer which uses a VSS sensor and not a cable. This is an easier option as far as calibrating your speedometer: https://www.summitracing.com/parts/fms-m4209adptac

Instructions: http://www.jegs.com/InstallationInstructions/300/397/397-speed.pdf

Edit:

Your AOD has an 8 tooth drive gear. With 3.73s in my Thunderbird I've been running a black 23 tooth driven gear without issue for many years.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

3.73 speedo gear?

Reply #13 –
Quote from: kylesburrell;458991
So Im looking to put in an 8.8 rear with 3.73s. Tire size is 225/60/15. According to your link, AOD's have 8 tooth drive gear. So I need a 22.6 tooth speedo gear, so I should get a 23 tooth speedo gear, right?

And I might upgrade rear tires to 285/40/17. That gives me a 23.2 tooth speedo gear.

Just looking for some validation here. Thanks!
-Kyle


Kyle, just an FYI, if you haven't acquired an 8.8 with the 3.73, I have one in Manassas. It is still in the car right now.
 

3.73 speedo gear?

Reply #14 –
@Aerocoupe and thunderjet: Thanks, I think i'll just run a 23 tooth speedo gear on my VSS. Simple to swap out. Ive replaced my VSS about 4 yrs ago thinking that was causing the speedometer in my cluster to act up. NOPE! Cluster died :(

@50RACER, no thanks, I already have my 8.8 sitting in my garage. Waiting on some money to come in since the 8.8 is 5 lug. So im hunting for 17in 5x4.5 wheels/tires. But I appreciate the offer.

-Kyle
1986 Ford Thunderchicken, 5.0 AOD w/ Shift kit,  354,XXX miles. 1-Family owned. Original engine+trans.
8.8 Disc Rear w/ 3.73 Posi. CHE Control Arms. '04 Cobra brakes all around. 2000 Cobra R wheels. Tubular front LCA's. MM Steering Shaft. Unlocked Speedo, Lowering springs, Eibach sway bars front and rear. Ram air intake.