I think that stang6790 and Aussie might be correct. If i were to multiply 1.4 by 2 it will equal about 2.79 which is what i am supposed to have. It just seems like too much of a coincidence. Thanks for all your help, i'll go outside in alittle bit and try the test over again but his time spinning the driveshaft and see what happens.
Matt

 

Yes that is correct.

 

Correct. Like Thumpin posted, it doesn't matter if you having a locking differential, but otherwise you need one tire on the ground or fixed in some other way to figure the differential ratio by turning a tire.

 

i'm getting different outcomes. When i tape the ds and the wheel i get about a 2.80 ratio. with a 225 45 r18 tire my diameter is 25.97. On speedworldmotorplex.com i enter my diameter, and speed and it told me i have a 3.31 ratio, what's the deal?

 

Speedo is off. Use the tach to get an accurate reading through ratios. Either that, or you have an auto....

 

i bought that size tire so it would stay as close to factory as possible. With that diameter at 70 mph and 3000 rpm it says 3.31, and yes it's a auto.

 

stock 69 is 205 75 14 which is 26.11 diameter. At 3000 rpm and 70 mph it shows to have a 3.33 ratio.

 

Do you have overdrive?

 

nope , is there a different way to figure it out?

 

Your auto is throwing off the rpm's at speed. They will naturally run higher rpm's than a manual with the same gears due to the torque converter slipping. 500 rpm seems to be an excessive amount of slip, but that isn't too far off, really.