Ford 9" axles
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Junior User
Joined: May 2005
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From: Clovis,CA.
Ford 9" axles
Icurrently have a 31 spline 9" rear dif in my truck I would like to know what I need to do to change it to 35 or 40 splined axles? Is it as easy as changing the side gears in the drop out? Or would I need to change the axle tube ends? I hate to part wityh it if I can upgrade it to handle 38"-42" tires.
Post Fiend
Joined: May 2006
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From: Central Florida
My 9" with 31splines was more than capable of handling my 36's. In fact, it was the pinion gear that gave out first.
To swap from 31 to 35 spline, you will need a new diff and the axles. The differential is splined and accepts the axles.
To swap from 31 to 35 spline, you will need a new diff and the axles. The differential is splined and accepts the axles.
Elder User
Joined: Feb 2004
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From: San Luis Obispo, CA
Ford made 28-spline and 31-spline axles in the 9". You can change between them by changing the differential side gears. I cannot see how 40-spline or even 35-spline axles could fit through the stock carrier holes. I think you would need at least a whole new "pumpkin".
The spline pitch is constant, so the axle gets bigger fast with the numbers you are mentioning. I'll watch this thread and see if I can learn something new.
The spline pitch is constant, so the axle gets bigger fast with the numbers you are mentioning. I'll watch this thread and see if I can learn something new.
Elder User
Joined: Feb 2004
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From: San Luis Obispo, CA
Which bearings are you speaking of? I do think now, that there are two different axle bearings to keep track of, but the bottom line is that the axle end has to go through the hole in the differential carrier before it can get to the side gears. I know that 31-spline axles exist - I have had one in my hands and it did not fit in place of a 28-spline (big surprise). Somebody should post on whether a 9" can handle a bigger axle than 31 splines.
Posting Guru
Joined: Nov 2003
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From: East Flat Rock NC
If your 31 spline carrier has the big bearings then you should be okay.
The axle supplier will size the bearings appropriately to the axle you are buying especially if you are buying a spool too. (of the Hogshead)
Wally Womack
ps...
3.062" bearing size will only handle fewer then 35 spline
3.250" bearing size will handle up to 40 spline
ps... you can have a bearing sent to you from a spool manufacturer that will step that bearing for the 28 spline up to an interior size that will fit a 31 spline.
I have done it.
The axle supplier will size the bearings appropriately to the axle you are buying especially if you are buying a spool too. (of the Hogshead)
Wally Womack
ps...
3.062" bearing size will only handle fewer then 35 spline
3.250" bearing size will handle up to 40 spline
ps... you can have a bearing sent to you from a spool manufacturer that will step that bearing for the 28 spline up to an interior size that will fit a 31 spline.
I have done it.
Last edited by Pro-Street/StateTK; Apr 3, 2007 at 09:32 PM.
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Posting Guru
Joined: Nov 2005
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From: Madison, SD
There are 35 and 40 spline axles available for the 9" rear ends, takes a matching carrier or spool, of course. I built a '67 Comet tube frame drag car for a guy back in 1995. The car runs Super Gas (9.90's @ mid 140's). I put 40 spline axles and spool in the car. After hundreds of passes the car has bent a couple pinions, and trashed a couple sets of gears but the 40 spline axles are still alive and doing fine with not so much as a twisted spline!!! The 35 and 40 spline axles do require the Big housing end and bearing. They cost a few $$$$ more, but they are as close to bulletproof as parts can be....
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Postmaster
Joined: Nov 2001
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From: Escondido, CA
Check out ebay. There is a site store that sells former NASCAR parts for a decent price. They carry the "B", 3.062 and smaller stock bearing, and the "H", 3.250 bearing, case carriers. Most of the time you will see Detroit Lockers and ring ger sets on there as well. I would also suggest checking out the Moser axle site. There is a axle spline calculator that will help deterine what size splined axles are needed for your truck. Their custom built axles are priced really good as well. Plus if you need to respline them later down the road they will do it at a drastically reduced price or free of charge if I remember right.
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Junior User
Joined: May 2005
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From: Clovis,CA.
Thanks, I checked with Moser and they can make me custom 40 spline full floaters and yhey will fit in my housing just under 1k for all the stuff.So now I will try to get a front 9" setup...time tio check Sunray Engineering on a cost for the 1550 axle setup for the front.
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