Fox T-Bird/Cougar Forums

Technical => Drivetrain Tech => Topic started by: vinnietbird on July 21, 2007, 04:40:34 PM

Title: Which speedo gear
Post by: vinnietbird on July 21, 2007, 04:40:34 PM
Which speedo gear do I need for an AOD and 3.55 gears?
Title: Which speedo gear
Post by: gumby on July 21, 2007, 04:59:41 PM
what tires size? how many drive teeth on the AOD speedo drive gear?


this (http://www.ffcobra.com/FAQ/speedo.html)  is the calculator i use. scroll down for calculators, part numbers, and driven gear colors
Title: Which speedo gear
Post by: vinnietbird on July 21, 2007, 05:07:59 PM
my tires are 255 40 17 and as far as how many teeth the aod inner gear is,how the  do I know.I know the gear I have now is for a 2.73 rear.
Title: Which speedo gear
Post by: gumby on July 21, 2007, 05:12:00 PM
hrrmmm, try findin an AOD specific speedo gear calculator?
i know how many teeth T5's use, but i cant help ya on AOD stuff.....
Title: Which speedo gear
Post by: Tbird232ci on July 21, 2007, 05:19:54 PM
I recall reading somewhere that they are either 6 or 7 tooth. Have you done a search here, I think someone said that that was one of the differences between the mustang and tbird AOD's. Its been a while.
Title: Which speedo gear
Post by: Kitz Kat on July 21, 2007, 06:24:41 PM
If it's an original TB v-8 it should be 7 tooth.Mine was but I don't
know if it was original.
Title: Which speedo gear
Post by: gumby on July 21, 2007, 06:48:28 PM
ok then. calculator says 20tooth driven gear(p/n C8SZ-17271-B, orange) for 25" tire, 3.55 rear gear, and 7 tooth drive gear auto.

that page also states AOD's use 7 or 8 tooth drive gears, but i dont see any info on determining which you have.


*edit, what color is your stock driven gear for 2.73's, and what was the stock tire size? we can work backwards and figure out what drive gear you have.
Title: Which speedo gear
Post by: dominator on July 21, 2007, 08:28:55 PM
Aod's out of bird's and cougs are 8 tooth drive,mustangs aod's are 7 tooth drive and t5 manuals are 6 tooth.
There is no ford gear for what you want to do vinnie,you have to go with an aftermarket 23 tooth off of ebay.
I had one once before i put in the stang aod, it lasted 2 months before loosing teeth due to the thiness of the gear.
My current aod is from a stang and is a 7 tooth drive with a ford 21tooth(highest ford aod gear) with 3.73s and it is within 1 km+ - on the dyno.
With my old bird aod(8 tooth drive) i had to go with a 23tooth to make it accurate with the 3.73s.
The max gear you can use and still use a ford 21tooth speedo gear is 3.27s,otherwise you just have to live with it being inaccurate.
Title: Which speedo gear
Post by: vinnietbird on July 22, 2007, 09:26:13 AM
I'll try a 23 tooth gear and have someone pace me on the highway.Thanks a lot.
Title: Which speedo gear
Post by: vinnietbird on July 22, 2007, 09:27:13 AM
Oh,this 23 tooth gear,....I've seen them for 5 speeds,but not aod's on ebay..
Title: Which speedo gear
Post by: 347Thunder on July 22, 2007, 09:57:36 AM
try ford racing they sell all the different sizes
Title: Which speedo gear
Post by: vinnietbird on July 22, 2007, 10:33:17 AM
10-4 and thanks.
Title: Which speedo gear
Post by: Ether947 on July 22, 2007, 08:42:18 PM
I got a 4-pack of speedo gears from CJ Pony. They are for sale but they are for a T-5. I think they have AOD gears as well.
Title: Which speedo gear
Post by: grutinator on July 22, 2007, 08:56:48 PM
just a side question...

how much would getting bigger wheels and tires(overall diameter) change the difference in the speedo gear. for example, if he needed a 23 tooth gear and could only find a 21, would that compensate for the difference much? i ask 'cus either 3.55's or 3.73 are the next planned mod, i wanna know what im up against.
Title: Which speedo gear
Post by: thunderjet302 on July 22, 2007, 09:13:17 PM
http://www.mustangsunlimited.com/itemdy01.asp?T1=DFM17271J+01&Category=Drivetrain&subCategory=Speedometer+Gears&CatKey=74-01

Have had this in mine for over a year with no problems. If you have the stock AOD like me this is the one you need.
Title: Which speedo gear
Post by: blackcougar71 on August 19, 2007, 05:22:44 PM
what speedo gear would i use for this combo- rear end gear ratio 5.13, c5 transmission, rims i am going to use are 16' dont know what size tire yet?
Title: Which speedo gear
Post by: t.birdsc on August 19, 2007, 05:52:43 PM
Quote from: blackcougar71;170348
what speedo gear would i use for this combo- rear end gear ratio 5.13, c5 transmission, rims i am going to use are 16' dont know what size tire yet?



:evilgrin: 5.13 gear? :evilgrin:  that's enough gear to rotate the earth! :evilgrin:
Title: Which speedo gear
Post by: vinnietbird on August 19, 2007, 06:23:38 PM
When you're running a car with those gears,do you really NEEEEEEED a speedo???
Title: Which speedo gear
Post by: blackcougar71 on August 19, 2007, 07:59:44 PM
yeah because my cougar that is going to have those gears in it is going to be my daily driver. so a speedo is needed around city streets. then my other car when i get it is a 85 turbocoupe to be a beast on the street/track just like my cougar. so is there a speedo gear for my cougar setup?
Title: Which speedo gear
Post by: TurboCoupe50 on August 19, 2007, 08:58:40 PM
There is no gear that will even be remotely close for 5.13 cogs...

In the old days they had adapters(a small gear box) that mounted into the transmission and the cable(with gear) went into the adapter... By juggling gears in each you could come up with about any combo imaginable...

That much gear on a C5 is going to get real old in a BIG hurry... Be like driving in second gear...
Title: Which speedo gear
Post by: atariman on August 19, 2007, 09:08:34 PM
What would I use?
275/60-15 on 15" rims, c4, 3:50 rear gear.

 I think I got a purple gear in there now. I know it off.
:birdsmily:
Title: Which speedo gear
Post by: blackcougar71 on August 21, 2007, 07:23:10 PM
then what about 4.56 gears for my rear end?
Title: Which speedo gear
Post by: dominator on August 21, 2007, 07:46:57 PM
How about 4:10s tops for the street and even that is to much gear!!
3.73's would still be high for a 3speed but would be much closer with a 23tooth.
Title: Which speedo gear
Post by: thunderjet302 on August 22, 2007, 12:28:33 AM
Do they even make a 5.13 8.8" ring gear?
Title: Which speedo gear
Post by: gumby on August 22, 2007, 06:33:56 AM
yes
Title: Which speedo gear
Post by: blackcougar71 on August 22, 2007, 08:52:21 AM
8.8 with 5.13s are dirt cheap like $100-300 on ebay i seen them there a few month ago.
Title: Which speedo gear
Post by: thunderjet302 on August 22, 2007, 05:21:43 PM
Quote from: gumby;171084
yes


Really? Wow. It be hell to drive that on the street:toilet: