Well an update I picked my truck up today and I downloaded a GPS app on my IPONE I set the cruise control on my truck at 55 mph the gps said I was doing 44mph. Then I set the cruise at 65mph the gps said I was doing 52mph. im gonna take my stock truck out and check the GPS here in a mintue. I lowered the mm to 2600 before doing the testing and I have the 3.73 gear set so I dont know why its so far off.

 

I think it is time to manually check your gears, to verify they are really 3.73. That is what I would do.

 

Anyway besides pulling the rear end cover??

 

Yep. Put the rear of the truck on jack stands with the front wheels scotched. Put it in neutral. On the inside of a rear tire, make a chalk mark at the bottom and make "line up" mark on the ground so that it is indexed. Then make a mark on the drive shaft to align it with something as an index so you can count revolutions. Turn the tire one complete revolution till the marks realign. As you rotate the tire, count how many turns you get on the drive shaft. If it is about 3 1/2, it would be a 3.55, if about 3 3/4 it would be a 3.73 and if just over 4, it would be a 4.11.

 

Holly crap haha. It has a 6 inch lift and I dont have jack stands haha

 

OK, then plan B. Get an assistant. Mark the outside of a tire, straight down. mark the driveshaft as previously indicated. get someone to roll the truck one revolution of the tire and count the revolutions of the driveshaft as it rolls.

 

Some day, you will need to jack that thing off the ground, you better get some stands that will go under the axle before that happens!

 

Tell the device you have 4.56 gears and do another GPS run.

 

I wonder if the tag on the differential would have been changed if the gears were changed?

It's really beginning to sound like the truck had new gears installed with the lift and bigger tires. (It would have been a smart move.)

- Jack

 

I did the math, and I'm pretty sure it has 4.56's. I'm betting if you put 4.56 into the Edge it will be damn close.

 

I wouldnt be suprised the guy that owned it before me dumped alot of money in it. Of course I used to be that guy that dumped all kinds of money into trucks and lost my a$$.

Now would it be 456 or 455 gears is the question ill go do it now for ****s n giggles.

 

I got buddys that own tire shops why do I need to lift this thing off the ground one day for?

Ill be honest my first truck was a 1966 Chevy i got burned out on wrenching on cars Ill do a starter or something simple like that every now and then but thats about it.

 

they come in 4.11, and 4.56. Maybe 4.33, not sure about those.

 

Im gonna go try the 456 brb

 

well I put 456 in for gears and 2600mm for tires and im with in 1mph

The bad news now is I know why I race from gas station to station haha