B-4000 rear end replacement

[ComboFix2001]

2007 Mazda B4000 4.0L MT 4X4 CAB PLUS

Recently snapped a rear axial, chose to replace the entire rear end.

Went to a local wrecking yard to swap out a used rear end from a ford. I counted the teeth on the ring gear before replacing it.

After swapping the rear ends, once put into 4x4 the rear tires seem to load up and drag or skip behind. It is hard to tell which is happening form inside the vehicle.

Regardless of if its dragging or skipping, I assume it is doing this because of a gear ratio difference between the front and rear end.

Unfortunately, I was told that the 4x4 worked. Only now I am learning this is the second possibly 3rd rear end put into this truck. Also the previous owner was unsure if the 4x4 actually worked at the time of the last rear end being in the truck.

I have no issue going back and getting a new used rear end. However I would need to be 100% certain it is the correct one.

Does anyone have some advice to know for certain which rear end I am suppose to be putting in this truck? What should I be looking at, and how do I know what I am looking at will work in my truck?
Thanks!

 

[sgtsandman]

Assuming the front differential is still the original, you could try looking up the axle code for what ring and pinion is in it and is supposed to be in the rear.

Lifting the front up off the ground and counting the number of times the driveshaft turns compared to a single rotation of the tire. 3.73 won't be quite 4 rotations and 4.10 will be slightly more than 4.

The only way to know for sure is to drop the differential so you can look at the numbers on the side of the ring gear. The ratio should be there. The same goes for rear axle, there should be a gear ratio number on the side of the ring gear. If memory serves, there is also a ratio number on the end of the pinion gear as well but you usually can't see that easily without pulling the carrier out of the differential.

Obviously, both need to be the same. It sounds like they are not from what you are describing.