Hello, I’m new here to the forum. I’ve been looking around online for some advice on doing a rear end swap. My truck has the typical 9.75” 3.73 open diff but it leaked fluid and now it whines like crazy. Two shops wanted $2000 for a rebuild, the trucks got 187k miles so that’s not worth it to me.

On the other hand, I’ve found a 127k mile rear end on eBay for $830. Same axle ratio and gear size, it’s off of a wrecked truck with NO rust, and it has limited slip.

The best case scenario would be that it arrives in one piece, I’m able to do the swap in a few hours, and I end up with a quiet rear now with LS. The problem is I’ve never had to do a rear end swap, so I’m unsure of what kind of worst case scenarios could arise. At the moment I’m planning this solely based on YouTube education lol.

I’d appreciate any helpful tips or advice y'all can give. Honestly my biggest concern is getting the brakes swapped over right, because if that goes wrong I’ll need a lot more than a new rear end. 😅

 

Brakes should be easy.

Worst case is probably a different pinion yoke so you might have to hunt for a crossover joint, but I'd say this is unlikely as they're probably both flanges. Speaking of, be sure you have the appropriate 12 point wrench for the 12 pt bolts Ford loves

Please don't reuse u-bolts

 

Be prepared for having to redo the hard brake lines on the newer rear end, they could get bent to smashed in shipping. Make sure you hav some brake wrenches for this. I'd just do the brakes at the same time. As long as it's another 9.75" from the same years it should be straight forward. Change the diff gear oil ( it does require an additive for the LS, but I'd skip that, see below). and flush the brake fluid and run it.

I'd not count on the limited slip being worth anything. Those limited slips weren't limiting much slip to begin with and wear out quickly, like 30k miles and worthless.

 

Hey all thanks for the replies and advice. I’m going to keep doing research and weight out all of my options.