Hey guys, I picked up a ford 9" out of a truck that I plan on using the center section out of for my third gen. It's just sitting in the garage right now. I plan on purchasing the moser housing and axle kit. My question is how do I go about tearing down the 9" i have in the garage? I want to see what spline axles / carrier has. I also just want to see if it came with a posi and what gear ratio it has.

If I lucked out this may be a cheap swap. Please let me know if you have any tips for disassembly for my cheap 9" in my garage.

Regards.

 

http://www.lt1howto.com/articles/diy9inch.htm

This link might help...

 

Make sure it's a 9" and not a 8". Use the lowest bolt on the 3rd member try putting a socket with extension on it. If it fits its a 8 inch if you can't get it on (hits case) its a 9 inch.

Like you already mentioned you'll need to check out the splines on the center section before ordering your axle kit. If they don't match there not going to fit.

 

Could you please elaborate on disifering if it's a 9" or 8"?

Thanks,

 

If you can use a socket to remove all the bottom housing bolts then it's an 8". A 9" needs a wrench to remove at least one of the bottom bolts.

As mentioned above, make sure it's a 9" and not an 8". Find out the spline count before ordering axles. Ford made 28 and 31 spline carriers. I wouldn't even recommend the 28 splines for a street car. If yours isn't 31 spline, take it back and find one with 31 spines or buy a new 31 spline posi. The posis do wear out. Chances are it would need a rebuild anyway.

 

Thanks for the info. So if mine is a 9" and winds up being a 28 spline carrier, I can swap out for a 31 spline carrier and still use the center section? Also, I was hoping for sort of an in-depth how-to on how to take the centersection out. This way I can look everything over and discard the housing and axles.

Thanks,

 

I'm no expert but I would say yes you should be able to swap them and I imagine that changing a spool/posi carrier you would need to adjust your backlash spacing again.

I would agree on the 28 splines also. I've seen some guys on here convert 9 bolt axle tubes to a 28 spline thirdmember. Most of the street guys are running 31 or 35 splines though.

Also to point out if you want a specific posi in the future like a new WaveTrac (expensive but lifetime warranty) I'm pretty sure they only offer those in 35 spline currently. Just another thing to think about when picking out the splines you want, else you may end up forking over money again for new axles down the road.

 

A 35 spline carrier won't fit in an OEM case without using a special carrier and bearings. You would need to buy a big bearing aftermarket case to use a normal 35 spline carrier. The majority of the older OEM cases use a small 2.892" bearing and most of the newer cases use a 3.062" side bearing. An aftermarket case with 3.250" bearings can handle up to 40 spline axles. It is possible to easily upgrade to a 33 spline axles with a 3.062" case.

Check the casting number inside the case. It's probably a C7AW-E

For axles size, bigger isn't always better. You only need an axle large enough so that a single axle can withstand the total amount of torque placed on it. Moser had a calculator on their web site but have removed it.

Basically it's maximum engine torque X tranny first gear X diff gear X .9

Lets say your engine can produce 500 pounds of torque (engine dyno sheet). You use a 700R4 tranny with a 3.06 first gear and you have 3.73 gears.

500 x 3.06 x 3.73 x .9 = 5136.2

Moser lists their axles as how munch torque a single axle can withstand and one axle needs to be greater than what you can produce. They don't even list a 28 spline axle.

30 spline = 6200
31 spline = 7000
33 spline = 8200
35 spline = 9600
40 spline = 12000

Based on the above numbers, 28 spline axles could probably survive but 31 spline would be better. 33 or 35 spline is overkill. Too big of an axle can actually slow you down.

My car only uses 31 spline axles because it's all I need. Estimated torque is around 800. Probably higher but that's the number I use. 1.76 first gear powerglide. 4.86 in the diff.

800 x 1.76 x 4.86 x .9 = 6158 pounds of torque which isn't a whole lot more than the example above. Even upping my estimated torque to 900 increases the total to 6928 which is just below the limits of 31 spline axles. Technically, I should upgrade to 33 spline but I haven't seen my axles or axle splines twisting yet. I pull them periodically to check them. If I used a 3 speed tranny, I would need at least 35 spline axles and probably 40 spline.

 

Great information guys. I'll keep this in mind. Will more than likely go for 31 spline so I can use the OE case. How do I go about pulling the center section out of the housing? I've never messed with one of these before and I'm not sure what it all entails. Please let me know.

Thanks,

 

Pull the axles, unbolt all the bolts holding the housing in and drop it out. You may need to use screwdrivers, prybar, putty knife etc if there's a bunch of silicone holding it in.