'05 f150 4x4 rear differential question
 

Helping my cousin with his '05 f150 and his rear differential has gone out. The ring and pinion are 3.55:1 and its an 8.8. I am just trying to figure out if an older year differential will work as long as I still use the the old ring and pinion since its 4x4. Any help would be greatly appreciated.

Wouldn't it be better to repair/rebuild the differential instead of finding a used unit that could very well do the same thing a week after you install it?

As to ring and pinion gears, you would not have to make a swap in a use unit if the used unit has the same gear ratio.

Setting up a ring and pinion is an art.

That is actually exactly what I have decided to do I was able to find the differential gears easier and cheaper than expected so we have them ordered and gonna start the project tomorrow.