Rear End Location

[ryanbrown0311]

Does any one know of or have a 9" that sits on the springs rather than under like my Danna, I am looking to change to a 9" for Taller gears and would like to find a direct replacement rather than having to cut and reweld the spring perches.

[FORDification]

The only 'direct replacement' will be from a '65-'72 truck. Any other rearend will have to have the perches relocated, either due to a difference in mounting width (frame width) or type of rear spring (coil or leaf). Or the rearend itself might be too narrow, depending on it's original application.

Also, our trucks take a 28-spline axle, whereas most performance applications take a 31-spline...and while you might be able to find a pair of the proper-width 31-spline axles to fit the housing, don't hold your breath. They'd be very hard to find, or fairly expensive to get custom-made.

Why not just put a regular truck 9" in there and replace the gears with the ratio you need?

[xxxtina63]

You mean springs under the axle? Must be lowering an F250 (hopefully not a 4x4). Look for one under full size cars. None of the trucks had leaf springs under the axle tubes. Make sure you can identify a 9 in. from an 8 in. They're similar looking, especially if you're lying in mud under a junk donor.

[ryanbrown0311]

I need to swap out to a high 2 and the tallest they make for a Danna 60 Is a 3.5, I'm not wanting to lower it as much as I'm dealing with a center of gravity/traction issue, my 460 puts too much down an she wont hook up. At 1/2 pedal in 2nd I'm smokin. so I figure taller gears and some traction bars might do the trick, I don't want to add weight, and I've already changed the pinion angle for more down force,

[FORDification]

Well, you can swap in the pumpkin from a 9" in a big boat like a Galaxie/LTD which would have those highway gears, but you'd have to have the axles shortened and resplined to match up. Depending on the style of axles you currently have (tapered or not), you might have to replace the axles.

Most 6-cylinder half-ton trucks had lower gears. My '67 SWB F100 with a I6/3-spd has 3.00:1 ratio, as does my '72 SWB F100 with a 302/3-spd combo.

You could also go to a wider and softer-compound tire to get more grip, though the street life of those softer tires is going to be shortened somewhat.

Here's a few links on 9" rearends to read, if you don't already know about them:

http://www.kevinstang.com/Ninecase.htm
http://www.mustangsandmore.com/ubb/Ford ... sions.html

[ryanbrown0311]

Right now I am running a 3.73:1 gear so a 2.86:1 would essentially make my present 2nd gear my new 1st gear. As far as tires go I am running BF Goodrich Radial T/A's @ 295-50-R16 I don't know enough about tire size to know what would be bigger.

[fordman]

your running 50's on the back. man those are wide

[xxxtina63]

You must get the sides of the box dirty on a regular basis. Can we say "fender flares"? Just kidding, don't do it! One thing to take into consideration is tire height, or circumference. As the distance around the tire increases, RPM's and effective gear ratio decreases. If you switched to say a 295/60-16, the sidewall would be 60% of 295mm which is 177mm. The 50 series is only 147.5mm high.

295mm x .6 = 177mm/25.4mm= 6.968 inches x 2=13.937 + 16=29.937in.

295mm x .5 =147.5mm/25.4mm=5.807inches x 2=11.61 + 16=27.614in.

See, the difference in tire height is almost 2 1/4 inches. What you're running now is short and very fat. If you increase tire height or circumference (the distance around the tire) you have effectively reduced your gear ratio. This is why the 4x4 guys have to resort to deeper (lower) gears when increasing tire size. Hope this helps.

[FORDification]

Hey, here's what you need....this is a 9" center section from a Lincoln with a 2.75 ratio.....and it's even set up for 28-spline axles.

http://cgi.ebay.com/ebaymotors/Ford-9in ... 6081QQrdZ1

Just grab the 9" setup from any '65-'72 Ford pickup and swap in this center section (and replace the flange drive with a yoke), and you're set. Your takeoff will lose a little, but the top-end will sure surprise you.

(...however, out on the interstate, just be sure to roll up all windows after 130 MPH!)