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i got a 91 xr7 with a 5.0 and there are 2 different part numbers for this model. one is for a trans with a 7 tooth gear and the other is for a 8 tooth. how could i find out? thanks

also the 8tooth is 100$ more.
 

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do you need a replacement gear? crawl under the car and unbolt the one bolt holding the vss to the tailshaft of the tranny on the driver side. the gear is inside the vss. count the number of teeth.

and how can a little plastic gear even cost $100? hope thats a typo...
 

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i just realized i forgot to mention the part numbers were for the transmissions then selves but the description said one trans was an 8 tooth and the other a 7 tooth. the 8 tooth trans was 8xx and the 7 tooth was 720
 

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big mike said:
do you need a replacement gear? crawl under the car and unbolt the one bolt holding the vss to the tailshaft of the tranny on the driver side. the gear is inside the vss. count the number of teeth.

and how can a little plastic gear even cost $100? hope thats a typo...
He's referring to the drive gear inside the transmission.
 

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I don't remember which one my 89 3.8 Cougar had, but the replacement AOD from a V8 mustang was the other one. The tranny shop tried to get it right (pacing the car with a truck with 4 different sized tires, rags stuffed into the fuel fillers, among other rednecky stuff) but I eventually took it to a speedometer shop with a syno to get it right.

Obviously there is another difference that names it 100 dollars difference for the tranny. It would be best to get the one with the same number of teeth on the output shaft if all else is equal. The gear to get the speedometer right is 10-20 bucks.
 

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The driven gear is machined into the output shaft of the transmission. Buy the cheaper one. If it's the wrong one, a new driven gear is $20, so you still come out $80 ahead. Go to www.fordracingparts.com and download a catalog. Page 139 has all the speedo gear info you'll need. If you have 3.08 gears and the 7-tooth drive gear, you'll need the 18-tooth driven gear (Gray). For 3.27 gears, you'll need the 19-tooth gear (tan).

Come to think of it, what color is your driven gear, the one on the VSS?
 

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If you're talking about an AOD, the speedo drive gear is machined in the output shaft of the trans ... it's not a separate plastic gear like some other transmissions.

Ford parts catalogue shows an output shaft with a 7-tooth gear for 91 Cougar.


cheers
Ed N.
 

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91 is a questionable year. The SC's were 8 tooth, what gears does your car have stock? That should be a good clue. It really doesn't make a difference you can change the plastic gear to match. You can use the 8 tooth shaft with up to 3.27:1 gears. The 7 tooth shaft can be used with up to 3.73:1 gears.
Alan
 

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big mike said:
that aint what the title says :tongue:

Yes it does. The drive gear inside the transmission IS one of the two speedo gears.
 
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