speedometer gear question

[BigPip]

I just finished installing a new transmission and now the speedometer is off a bit. I didn't change my original gear, It is all original - speedo says 50 actual it's somewhere between 41-43 mph. I have a 93 and the trans is supposedly out of a 98 mark viii. Any suggestions on what I need to get it right? Obviously a new speedo gear but I don't know which one but I currently have a green gear.

 

[chris2523]

take the VSS and gear out of your old transmission and swap them.

was this a 98 LSC then?
but 8 mph at 50 is excessive for the 3.27/3.08 difference.

 

[BigPip]

there was no vss gear in the trans when I picked it up.

 

[chris2523]

so you are using your VSS and gear right now then correct?

 

[BigPip]

so you are using your VSS and gear right now then correct?

Yes, the one original to the car.

 

[BigPip]

I think the problem is my factory trans was a 7 tooth and the new trans is an 8 tooth. So now I need to find what tooth was used for a factory mark with 8 tooth. Shouldn't be too hard to find...

 

[Markviiiedrea]

I think the problem is my factory trans was a 7 tooth and the new trans is an 8 tooth. So now I need to find what tooth was used for a factory mark with 8 tooth. Shouldn't be too hard to find...

http://www.tciauto.com/tc/speedometer-gear-calculator/

 

[Necrosan]

https://www.fordracingparts.com/download/tipsPDF/SpeedometerGearUsageChart.pdf

Simple to determine what you need by looking at this chart.

 

[chris2523]

I think the problem is my factory trans was a 7 tooth and the new trans is an 8 tooth. So now I need to find what tooth was used for a factory mark with 8 tooth. Shouldn't be too hard to find...

The math matches your guess.
Swap for a 20 tooth gear and you should be good to go.

 

[BigPip]

The math matches your guess.
Swap for a 20 tooth gear and you should be good to go.

every calculator I checked said the same, 18.6, so I opted for the tan 19 tooth. I was about to order it online which would have put me in for about $20 shipped. I took a chance and called Ford and I will have it tomorrow for a whopping $4.30.

 

[BigPip]

The math matches your guess.
Swap for a 20 tooth gear and you should be good to go.

Well, my 19 tooth was close but I am still off so I ordered the 20 tooth, I should have it tomorrow. Good thing these are only a few dollars from Ford!

 

[BigPip]

Finally, I got the 20 tooth put it ad now we are in business. All numbers match perfect!