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I am currently running a 9" traction lock with a 3.89 ring and pinion and 31 spline side gears. I also have a complete 9" center section with a 3.50 ring and pinion, traction lock and 28 splines side gears. I want to replace the 3.89 chunk with the 3.50 chunk. What is required (how difficult is it) to replace the 28 spline gears with new 31 spline side gears?
 

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31 spline and 28 spline refer to the axle shaft spline count. 31 spline axles being thicker than 28 spline. The ring and pinion and center section housing aren't the issue, it's the actual center section (i.e. traction lock). You have to have a center section that's the same spline count as your axles. Swapping out center sections is not difficult. You just need some specialty tools and know how to use them. You'll need a dial indicator, magnetic base and press to remove the ring gear from center section. There are ways to get around needing the press although. You need to understand how to setup the wear pattern on a differential.
 
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28 spline axles are pretty common, so you could change the center and the axles. You have to back off the axles to change the center anyway, so not much more to slide the out and slide in a different set.
 

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I'm putting a 5 speed in it and with the 3:50's I should be at around 2,200 rpm at 70 mph
I wouldn't bother swapping purely for interstate cruising, its easier to simply drive 5mph slower unless you are often driving for hours on the interstate. Just getting some 28 spline axles sounds like the way to go if you are going to swap, I doubt you are making enough power and beating on your car enough to truly need 31 spline axles anyway.
 

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I'm putting a 5 speed in it and with the 3:50's I should be at around 2,200 rpm at 70 mph
Maybe even lower. I’m running 3.73’s with a WCT5 and turn 2,200 at 70. Definitely doesn’t seem worth it for the work and expense. I’d just roll with the 3.89’s. You might like it.
 

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Easy Peasy May need a new carrier but the swap is easy especially on a 9 inch Ford
Of course I am a professional with a Ford Chassis Master Certificate
There are only pinion shims and the rest is fully adjustable
You should not have to mess with any of that
Just pull the carrier apart and swap the side gears
I may be mistaken but it is an easy job and if you find you need a different carrier
You can just reassemble yours and find parts later Easy Peasy
Yes I would charge about 800 bucks because I can and have all the stuff
Dial indicator on a magnetic base and a pinion depth gauge
Spanner wrenches and gear marking compound is all it takes
Total about 900 in tools
Changing ratios ang gearsets a bit more difficult but doable watch a video or two on YouTube
 

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Dimples
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Easy Peasy May need a new carrier but the swap is easy especially on a 9 inch Ford
Of course I am a professional with a Ford Chassis Master Certificate
There are only pinion shims and the rest is fully adjustable
You should not have to mess with any of that
Just pull the carrier apart and swap the side gears
I may be mistaken but it is an easy job and if you find you need a different carrier
You can just reassemble yours and find parts later Easy Peasy
Yes I would charge about 800 bucks because I can and have all the stuff
Dial indicator on a magnetic base and a pinion depth gauge
Spanner wrenches and gear marking compound is all it takes
Total about 900 in tools
Changing ratios ang gearsets a bit more difficult but doable watch a video or two on YouTube
LOL. Easy peasy indeed.
 

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Live so close to Moab and the high dollar Jeeps
Rear ends had to be a specialty
My kids needed shoes and college
Fords were a sideline as they seldom break
Unless you got an 8.8 or a 7.5
Or a dana 44 or 50 or 60 or 10.25 Sterling or 10.5 AAM
Like the new AAM but so many problems already the parts are on backorder
 
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