HElp Confused more then when i started speedo

[turbomustang]

Hey guy yeah i search and got really confused.

i have a 94 explorer with a 4.0 i got a m5od and manual tcase from a 91 explorer its got 3.73's in it and i am running 33's what speedo gear do i need thank YOU!!!....

p.s bad at math or i wouldn't be asking this question.

 

[turbomustang]

30 people and no one can help me

 

[Maniak]

I can figure it out, but I need more info..

What changed that makes you want to change the speedo gear?

If you only changed from an a4ld to an m50d the difference in gear ratio is about .04 (.75 for the a4ld and I blieve .79 for the m50d).

With that much difference, don't change your speedo gear (drive gear)..

If you changed other things I need to know how far off your speedo was before, what you changed and your driven gear size.

~Mark

 

[turbomustang]

i never drove the truck befor i lifted it and put 33's on it the 33's are the big change soo i dunno what its off?...

 

[Maniak]

Assuming the speedo was correct bofore and the ONLY thing you changed was the tires then you went from 29" tall tires to 33" tires (235x75 r15 to 33's)..

That is a 13% change (give or take a little since tires aren't always the advertised sized). That means you need to speed up your speedo by 13%. Take a look at what driven gear you have and take away 13% from the size and that will put you back to where you were.

If you changed gears and tire size at the same time we need to know what the factory gearing was for your truck (axle code found on the door sticker) and then I can tell you how much change you need in the driven gear (assuming you still have the factory speed gear)

~Mark

 

[turbomustang]

hey man the help it much appreciated the truck had 3.08's in it and then i put 3.73 and 5 speed and 33's

 

[Maniak]

changing the gears put your speedo 18% off (reads fast)...
changing the trans isn't worth mentioning
changing the tires moved your speedo 13% slower...

that means your speed is reading about 5% fast.. Soo look at your driven gear and get one that is 5% smaller which comes out to be 1 tooth

~Mark