8 3/4 posi unit change

dewsky said
I currently have an 8 3/4 with a 489 case with a set of 3.91 gears and a posi unit installed. I am wanting the make the car (75 Duster) a bit more friendly on the highway by installing a set of 3.23 gears. I have a complete rear end out of a D200 with a 489 case that has the gears, but it does not have Posi. My question is, how hard is it to swap the posi unit from case to case? I dont know, but I believe it's a stock unit with the posi.

The 3.23 is my favorite street ratio. In fact, it is so popular that the new Strange 60 9.75 rear ends that Dr. Diff sells now has the option for 3.23! Up to this point, the 3.55 was the lowest numerical we could get. Tire diameter certainly plays into how well this will work on the street too.

You are stepping into a fun project, so learn a ton and enjoy!