weird gear/speedo gear questions

[DmnStr8]

When I bought my car I was told it had 3.73's in it (I'm not sure if the seller did them or not, he seemed confused to as what had been done to the car. I figured out later that he bought it for a project barely drove it, let it sit for a year and then decided to sell it). The tranny is from a 92 so I know that the speedo will be off not matter what I do unless I get a 7 or 6 tooth drive gear or a gear reduction box. Right now the speedo is off by 5 mpg at 30mph (One of those radar boxes the cops leave by the side of the road helped). I'm not sure how much its off at any other speed but I think its about the same judging by traffic.

Anyhow, when I was under the car changing the tranny fluid I decided to pull the speedo cable and see what I had for a speedo gear. the gear was black and the drive gear looked white (later I found out that this isn't a color for this gear so I think I may have been mistaken). I found out that this is the gear for 3.08 rear gears for my year of tranny. Where these a stock gear for manual transmission mustangs in 92? I thought that they were only in autos.

If not, I'm not sure why I have it. One quess I had is that I really have 3.55 gears and that a previous owner not realizing that the drive gear changed in 92 trannys ordered the wrong one.

Would my speedo only be off my 5mph if I had 3.73s but a speedo gear for a 3.08?

Whats the easiest way to check my gears. Jack up the rear and have someone spin a tire while I count how many times the driveshaft rotates? I'm assuming that if I get 3 1/2 turns its 3.55s and if i get 3 3/4 its 3.73s. Right?

Thanks guys

 

[DmnStr8]

btt

 

[Maryland Stang]

3.08 was a option in '92 on 5 speeds. If the speedo was reading high by 5 or 6 mph then indeed the car has 3.73s. The correction factor from 3.08 to 3.73 is roughly 1.2.

 

[ss93cobra]

Count the teeth on the black gear. If it had 23, then you've got 3.73's. I believe the alternative count is 16, which is for stock 2.73 or 3.08's, can't remember which.

 

[notchback]

yes jack up the back...it's the only to tell w/out pulling off the diff cover.

5-speeds had 2.73's or 3.08's you can look on the tag in the door , where it says "ax" it will have m=2.73 , z=3.08 , or e= 3.27 (aod only option)

i think 5 mph diff is more like a 3.08 to 3.55 swap myself. but maybe not.

you can use those radar boxex for all kinds of speeds to check your speedo out....i did

oh btw....try this link

http://www.mindspring.com/~steveflyer/speedo_gear_select.htm

 

[DmnStr8]

Door tag won't tell me much since the car is a converted 4cyl. Engine and trans were from a wrecked 92 GT.

Well looks like I will be picking up a 23 tooth white gear. That should get it pretty close.

Thanks guys

 

[ss93cobra]

Door tag won't tell me much since the car is a converted 4cyl. Engine and trans were from a wrecked 92 GT.

Well looks like I will be picking up a 23 tooth white gear. That should get it pretty close.

Thanks guys

I tooth = 4.897 blah blah m.p.h. f.y.i so add or subtract the tooth count as necessary

 

[DmnStr8]

Hmmm I begining to think that I may have 3.55's then. Not too bad at least I will be able to get the speedo dead on.

Are the drive gear colors the same for ford OEM parts as aftermarket? I figure I will look at the drive gear as well. It would be my luck to get the right driven gear and then find out that i had a 7 tooth drive gear.

ie is the stock 8 tooth drive gear green and the seven tooth yellow?

Thanks

 

[Maryland Stang]

The 23 tooth white gear is the gear you would use for both the 3.73 and 3.55 gears.