Shortening the Differential

[ClassicGuy]

I have a question (don’t bash me, I’m still learning). I have a 70 shortbed. I want to fit some Intro wheels that are 22x12 for the rear. I know I have to get the rear end shortened in order to have them fit. Has anyone had this done before with those size wheels and if so can you please tell all measurements used. I’m going to tub it also and add a c notch.
Thank you all for your time
Posted via Mobile Device

[HO455]

You will need to determine what axle length you currently have to start.
When trying to fit the largest wheel possible you cannot rely on measurements from a different vehicle. There are too many manufacturing tolerances that can stack up and what works on on vehicle won't work on another identical vehicle.
You will need to mock up the tire you wish to run using a wheel fitment tool. They can be bought, rented, borrowed, and if your handy, home built using metal or wood.

Once you know exactly how the tire fits in the space you can then determine the best offset of the wheel t fit the space. Then you can determine how much you need the axle shortened.

I recommend looking at the Mark Williams website for more information. And if you need more information give them a call as they have always been very helpful.

https://www.markwilliams.com/tech-index.html

https://1320wheels-com.3dcartstores....Kit_p_147.html

https://www.rsracing.com/TechWheel.aspx#fitting

[C101972]

I bought the wider wheel tubs for mine, I also bought 20x12 wheels with 5-1/2” back spacing. Had to narrow the rear differential 3-1/2” per side using Moser axles with their Ford large axle bearings that has the c-clip eliminator. You need to figure out what back spacing you can get your wheels in. Mine where special order wheels which isn’t cheap. Good luck on your build and I hope that I helped you. Thanks
Posted via Mobile Device

[LS short box]

Leaf spring or coil spring truck?
Quick Performance out Iowa gets good reviews doing custom Ford (I know the horror) 9" rear ends. They can build about anything you want and may have already done exactly what are looking for.
As long as you are doing it I would upgrade to 1350 yokes and u-joints.

[C101972]

Mine is a coil spring truck, I used the 12” rotors and disc brake from CPP. I also used Yukon gears and a Detroit locker posi unit from quick performance. My rear differential is narrowed pretty much to the maximum, the calipers are close to the u bolt mounts.
Posted via Mobile Device

[C101972]

My mistake it’s a Eaton posi unit not Detroit locker. Yes go with 1350 yoke and u-joints.
Posted via Mobile Device

[ClassicGuy]

Thank you all for taking the time to give some advice. Much appreciated. It is a leaf spring truck but I will be doing a 4 link. The wheels I am getting are 20x12 with an 8 inch lip.

[special-K]

You guys are referring to the entire axle assembly as the differential. Sounds funny. You don't narrow a differential, that gets left alone. It's the rear, rear axle, or axle assembly that you are narrowing. The axle shafts and housings are what get shortened.