Correct speedometer gear for 99 4R + 3.73s?

[wood_e]

My spring project is to swap in my 3.73 t-lock pumpkin. It's the cast iron version, but for a completely set up, ready to swap pumpkin I couldn't pass it up.

Ever since I swapped my 99 Grand marquis trans in my speedometer has been at least 10-15mph off, 20 or so if I'm going 70+.

I would simply get a 3.73 gear for a 4R70W, but wait, I don't know if my trans has a 7 or 8 tooth output shaft.

Does anyone know how I can tell the difference? Should I just get the friggin' gear and try it out? I have a GPS that I've been using to check my speed.

 

[NoLimit95]

My spring project is to swap in my 3.73 t-lock pumpkin. It's the cast iron version, but for a completely set up, ready to swap pumpkin I couldn't pass it up.

Ever since I swapped my 99 Grand marquis trans in my speedometer has been at least 10-15mph off, 20 or so if I'm going 70+.

I would simply get a 3.73 gear for a 4R70W, but wait, I don't know if my trans has a 7 or 8 tooth output shaft.

Does anyone know how I can tell the difference? Should I just get the friggin' gear and try it out? I have a GPS that I've been using to check my speed.

When you changed the trans over to the 99, did you not swap speed sensors from the old one?

 

[wood_e]

I forgot to, so that's on my list...

 

[LaserSVT]

You want the purple one.

 

[wood_e]

ok I ordered a purple one! I hope I don't have an 8 tooth output shaft!

 

[m_maker]

ok I ordered a purple one! I hope I don't have an 8 tooth output shaft!

You do. Speedcal is more like what you need.

 

[wood_e]

Yeah I do need a speedcal :-( anyone need a purple gear???

 

[LaserSVT]

Yeah I do need a speedcal :-( anyone need a purple gear???

No, I just got mine for when I do my 3.73 swap this spring.