question about 93 5.0, 5spd with upgraded gears

[pjb153]

I just purchased a 93 5.0, 5spd vert with different gears. The seller told me they had 3.73 in the car. The speedo is off by about 10mph (reading higher).

I looked on 50Resto for a need speedo gear and the chart there does not have the gear listed for 93 5spd with 3.73. Is that because they are just not on the chart or could there be something with not having 3.73's in a 93??

How can I tell what gears are in the rear?

Here is the link to the chart. I am assuming if it it 3.73 it needs the 21 tooth.
http://www.latemodelrestoration.com/buyersguide/speedo-gear.aspx

I just found another chart that says 90-93 with 3.73 should use the 23 tooth.
http://www.muscularmustangs.com/gears.php

Thanks

 

[91notchbk]

Your speedo may be off 10mph at 70 mph. And at 10 mph your speedometer may be off 2 mph. Remember, the difference of speed is actually a percentage. So your speedometer will read an actual percentage of increase. For example if your car initially had 3.08 gears and you went to 3.73 gears. That is a 21 percent change. So your speedometer will read 21 percent higher than actual speed. The change in speed depends on actual speed.

To find out what gears you have jack the car up and support it on jack stands. Keep it in nuetral so you can rotate the driveshaft. Mark the drive shaft in relation to the axle housing. Also, mark each wheel in relation to the backing plate. Next rotate the pinion and count how many turns of the driveshaft it takes until the wheel marks rotate on revolution. If it rotates 3 and 3/34 turns it is a 3.73. If it rotates a little past 3 1/2 it is 3.55 gears and so on.

Lastly, there is not a speedo gear that will work with 3.73 without changing the output shaft drive gear. This requires you to disassemble the transmission. Most guys use a 23 tooth which is correct for a 3.55 gear. This will get you close using 3.73s. Also, the 23 tooth gear tends to wear out because the mesh with the output shaft gear is not perfect. The best solution is the replace the output shaft and drive gear as a pair. However, most guys with 3.73s just throw in the 23 tooth and are close. Your speedo will read approx. 5 percent higher than actual speed with the 23 tooth output gear. If you ever have the trans apart it would be a good idea to replace the drive gear while you are in there.

This thread has more info on the speedo gear.
http://forums.stangnet.com/showthread.php?t=687147&highlight=91notchbk

 

[pjb153]

Thanks.. looks like I need a friends help with that to mark everything properly.. which means the initial cost is a six pack of beer.

Guess it has to be done though... off to grab some brew.