Ford 9 inch differential (in 1/3 scale)

[gbritnell]

I have the engine and transmission so the next link in the driveline would be the differential. ok, actually it would be the driveshaft but that's the easy part.
The Ford 9 inch diff has a removable center section making it much easier to model than the 8.8 so this is the project. I have a friend who just happened to have an old unit laying around so I borrowed it to start taking dimensions and making drawings.
It has been sitting for some time so the first order of business was to give it a thorough cleaning followed by dis-assembly. Man that thing is heavy. I don't remember them being that heavy when I was 20.
With about 40 hours of measuring and drawing I had a plan of attack.
I started with a piece of 4 inch dia. 6061 aluminum, 2.00 thick. The piece was faced in the lathe to 1.800 thick and then moved to the mill for machining some flats.



With the overall sizes established the edges were picked up and the centers found and entered into the readout.

[gbritnell]

I cut the step for the mounting flange and then roughly knocked the corners off. The flange mounting holes and bearing cap holes were then drilled. The hole for the pinion shaft was also drilled and reamed.


The next step was to start removing stock from the inside of the housing. I always do the inside cavities first because there's something square to clamp to.


gbritnell

[gbritnell]

The bearing caps were made and screwed in place.


At this point there was a lot of rotary table work so the vise was removed, the table cleaned up and the rotary table set up.
I roughly locate the center with plug in the table and a brass center in the spindle followed by indicating.




gbritnell

[gbritnell]

Rather than lay out all the centers for the radii I put a center drilled hole in the center and use this to locate my centers. With the rotary table located on center and the numbers registered I offset the part in the opposite direction of the radius center and using a brass centering plug, locate the part and clamp it. The are 4 internal radii and 4 external radii that form gussets to strengthen the housing so these were machined.




gbritnell

[duckman]

OK I'll be the first to jump in, are the gears going to be hypoid. I have to say that's sure a "GEM" of an indicator.

[gbritnell]

With those radii finished I gave myself some layout lines for machining the radii on the bearing caps. I use the old fashioned method for center finding out of habit and not wanting to crank the table up and down to insert the longer ones. As an apprentice I learned about the chunk of modeling clay and phono needle for wiggling centerlines. The part was then stood up on edge, the centers picked up and clamped securely.




gbritnell

[gbritnell]

Now it was time to bore the holes for the bearings. I took the rotary table off and set up a small angle plate to clamp the block to. My vise jaws are only 1.50 deep and with most of the stock removed from the rear face there wasn't much to clamp to. I wiggled the lines but also double checked by indicating the end mill shank you see sticking out of the pinion hole. The contour radii can be off a little but these need to be right on.



gbritnell

[gbritnell]

With the boring operation finished the part was put back in the vise to step off the clearance radius for the ring gear. Rather than trying to come up with special cutters and setups to do such work I just lay out the steps in Autocad and with a ball mill remove the material, first with a .375 cutter followed by a .187 to clean up the corners.


gbritnell

[gbritnell]

The part was then flipped over and then pinion mounting flange holes were drilled and the hole bored out.


You can see I have given myself some layout lines for the ribs and flange. These give a starting point but ultimately I use the digitals for all of the work.
gbritnell

[outlawspeeder]

Keep cutting! That mini 9 is in there! I can see it coming out. PLEASE put something in the photo to show the real size. Great set ups.

[gbritnell]

From here on out it's a matter of removing stock to reveal the hidden housing lurking inside. I do use my rotary table for radiusing operations but with having to move all over the part it's sometimes easier just to step off the shapes with a ball mill. The size of the steps look big here but this will be the top contour of the main rib and after it is thinned down by further operations it won't take any time to blend out the steps. It's a matter of weighing the amount of steps to the short time it takes to bur and file them smooth.





It looks like the part has been hewn with an axe but have faith, it will take shape.
gbritnell

[gbritnell]

This is kind of like manual CNC'ing. Over, down, over, down, over down. See what I told you! There is a part hiding in there!




gbritnell

[gbritnell]

The part has all the contours machined. All that remains is to cut the stock from the front bottom of the pinion housing to provide access to the lower mounting bolt holes, well of course and quite a few hours of work with the Dremel and riffler files.




gbritnell

[gbritnell]

Here are a couple of pictures of the ring and pinion gears. If some of you will remember I had started a thread on cutting skew bevel gears awhile back in preparation to this project. If I couldn't make workable gears there wasn't really much reason to go any further with the project.



gbritnell

[gbritnell]

No hypoid gears. Hypoids are just a little to complex for my shop, well most shops for that matter unless you have a Gleason sitting around doing nothing. Even at that I don't know how small of a pitch commercial machines will cut. These calculate out to about 32 D.P.
gbritnell