What speedo gear for 3.90's?

[jonnystang]

Hey all just wondering what speedo gear would be correct for my 3.90's. I have had the gears in for almost a year and am just getting sick of all the extra miles and the wrong speedometer reading. Thanks again for you help.

 

[legalize420]

the 5.0 tech section has a whole list of speedo gear combinations. 6 tooth drive gear and a 19 tooth speedo gear for 3.90. the tranny needs to be opened up. the drive gear is on the mainshaft.

 

[The Green GT]

Do it right and spend the $100 and get a speedcal.

 

[SeventyMach1]

the tranny needs to be opened up. the drive gear is on the mainshaft.

 

[legalize420]

there is a gear inside the transmission that spins the speedo gear. the speedo gear can be replaced from outside but the drive gear is inside on the mainshaft.

 

[Pokageek]

there is a gear inside the transmission that spins the speedo gear. the speedo gear can be replaced from outside but the drive gear is inside on the mainshaft.

Yep. closest I could get mine was it says 10 mph more than what I am doing. Keeps me from speeding nayway. I am going to wait to open up the trans until I get a new trans, lol.

 

[Bosko5.0]

+1 on the speedcal

try ebay for a speedcal i bought myne for $50

install is quick and easy, accurate within .02% of speed and you can change it if you have bigger or smaller tires

also looking around i found that the 3.55 and up use the same speedo gear which would be inaccurate

 

[SeventyMach1]

there is a gear inside the transmission that spins the speedo gear. the speedo gear can be replaced from outside but the drive gear is inside on the mainshaft.

Agreed .... but most people never mention that. You can get pretty close without going that far. To be dead accurate, you do have to do that ..... or go SpeedCal.

 

[jonnystang]

I thought the speedcal was for obdII cars?

 

[silverstangman]

i forget what tooth i used on mine, i believe it was the one recommended for 3.73's as they had that or one for 4.10's, and even with that in it was still off by 4-5 mph.