guess the rear gears!!??

To find out the ratio of the rears, chock wheels so the truck won't roll, release brakes and place transmission out of gear. Jack up one side of the rear axle until that set of tires are off the ground. Place a mark on the tires for a refrence, and also place a mark on the driveshaft that aligns up with something so you will be able to refrence each revolution, and where the mark will stop in relation to where it started.

Now, turn the wheel two complete revolutions, stopping with the mark on the tires at the same place it started. At the same time watch the mark on the driveshaft, and count how many revolutions it turns. As an example, if the drivesahft turns 3 3/4 revolutions per 2 revolutions of the wheel, then you have a 3.70 ratio. This is a very accurate way to check rear ratios.

 

I've always done it like Stranger says, although the counting teeth and doing the division as 379exd describes work too if you have the stump out. Don't worry about the 1800 rpm's, won't hurt nothing, most shops set company trucks to at least 2150, mine is set at 2450 and I sometimes downshift at 1800 on hills and think nothing of cruising at 2000. Enjoy it, it's a good engine.

 

You only had the one wheel you turned off the ground didn't you? If you didn't you will get a wrong reading. You also must use the rear - rear, as the front - rear has to go through the power divider.

 

you have a direct drive 13 spd