How do you determine the rear end ratio. I know it is on the VIN somehow, but what is the code? Thanks for answering a beginner question.

 

Look in the glovebox, will be there, and no it is not in the VIN number.

 

what year truck you got my 06 not in the glove box.
do you have a g56 6 speed if you do you got 3.73 yeah I did not believe it either they are that low geared.

 

jack up rear end. put valve stem at bottom or 6 oclock position. use this to "mark" your tire spin the driveshaft until the valvestem is back at 6 oclock position. if the shaft spun 3 3/4 times you have 3.73 if it spun a "little" more than 4 than you have 4.10

 

Thanks for the tip. I still thought they put it in the glovebox.

And yes, if you ahve the 6 speed (which an 06 will have teh G56) you have the 3.73's

 

Not in the glove box.
Let me try again this way. I have the automatic with the OD and the stock tires (michlen) and wheels. At 70 mph in OD I am turning 1900-2000 rpm. Does this sound like the 3.73?

 

Yes, it's what I run at 70 with 3.73's
Cheers
Mike
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This is true IF both wheels turn the same amount.
If one rear wheel is still on the ground, then you must turn the lifted wheel two full turns.

 

Thanks for the info. I was hoping it is a 3.73. I pull a fairly light trailer (6800# loaded) That ought to be a good match. Got the part for the hitch (need to drop it 6 more inches over what I had on the F150 for the Dodge). So when I get it set up I will get to try it with the trailer.

 

yes the mph and rpm match our trucks with 3.73's.....