Hot Rods Model A 9 Inch Diff chopping time

Hi Guy's My Build Has started on my 1930 Model A Coupe.
I have the Body Off and the ch***is stripped ready to Box.
I have a Question Has anybody put a shortened 9 inch in the back of an A coupe?
If so How much did you chop off and How long are your Axels?
I have a F100 9 inch and a triangulated 4 link ready to go in but I have no idea how to measure it up and how much to chop off.
I am running fenders on it with a 15x6 rims all round.
I have a 46 inch drop axel front to go in it.
I need to keep the track the same as the original or within 50mm I think for Rego (Don't quote me on that length, I Have to re check the Reg's here in Australia).

Some other info on the Build for you;
its a 1930 A coupe steel body Californian car that I bought in Australia.
It will have no chop and run fenders.
9 inch and 4 link in the back I have a 31 spline centre.
Disk brake all round.
Now the fun Bit 460BBF and a C6 to make it move.
Here is a photo I will post more as it comes along.
Cheers Byron

 

Take it to a professional shop. Tell them if you want the pinion centered or not and what you want for a width (hub to hub, etc.). Make sure they straighten it and remove the paint for you before they start re***embly. That's the best and easiest way I know. Gary

 

9" Ford rear ends look good and at one time they were common and you could put a nice one together for cheap. Those days are gone. If you have scored a junk yard example the first thing you need to do is confirm that the gear ratio is going to work with your engine, transmission, and rear tire diameter. If you are lucky the transmission ratio will be on a tag under one of the nuts securing the "pumpkin" and the ratio will work for you. If you are really lucky it will be a limited slip. If the tag is off you can determine the ratio by holding one axle flange securely, turning the other and counting the number of revolutions the input yoke makes. If the ratio is not right you can continue to look or do a rebuild with a new, readily available ring and pinion set. Summit Racing and Jegs have the rebuild kits and ring and pinons.

Next is getting the width right. The best way is to mock your mounted up wheels and tires and take a measurement between the mounting surfaces. You can occasionally find a 9" axle that will work. The axle out of an early Bronco is pretty close. If your axle housing is too wide it can be narrowed, The best way is to buy new bearing and flange cups from a company like Currey of Moser. The original cups can also be cleaned up on a lathe and reused. This is a good way to go if you want to use the brake drums that came with the axle.

Next comes the axles themselves. Ford used two different spline counts; 28 for everyday cars and 31 for performance and some truck applications. For the typical hot rod both are OK.

Sometimes you can get lucky and narrow one side of the axle housing and leave the other stock. This cuts your axle shaft problem in two. I also know people who were lucky enough to find an axle from a different application that would work for them. Don't count on it. You can also cut a bit of spline off if necessary. If you do this make sure the spline fully seats in the receiving female spline in the center section.

Usually, you will need custom axles from someone like Currey or Moser. You can not cut and respline 28 spline axles. 31 spine axles can be cut and resplined. However, these do have a heat treated end and relatively short resplined cuts are impossible to make. My 32 Ford roadster has a 9" with 1 shortened 31 spline factory axle and one custom axle from Moser.

Complete, built to specs 9" axle ***emblies are available from Currey, Moser, and John's Industries.

Over it's production life span Ford made 9" axles with several different bearing cups and brake flanges. When you are sorting things out make sure all of your components will work together.

And one final note. It is possible to build a Ford 9" axle ***embly with mixed and matched parts that have no lubricant fill hole. If there is no fill hole in the pumpkin make sure you have one in your axle housing. Some housings have drain holes and most do not. You want one as it makes servicing much easier and much neater.

 

Thanks for the Input guy's.
The housing is in really good condition I just need to Finnish stripping off the paint and cut off the old brackets. The centre I have is a 31 spline 3.00:1 ratio The 460 and C6 are stock at the moment.
Bib thanks for the information. My rims are on back order and wont be here for 5 weeks so I'm guessing I may have to wait till they are in to set up the rear end.
I should be able to get the housing in the right spot though and weld the 4 link in place then cut down the tubes last?!?
Oh thanks for pointing out the Drain Plug I would never have noticed if you hadn't mentioned it.

 

I would cut the bearing cups off and do the set up before cutting the tubes to length and welding on the bearing cups. If you a making your own 4 link brackets you want them to do a 360 around the tubes. Welding on one side will twist the tube for sure. Welding all around seems to even the stress out and keep the tube straight.

I landed in Darwin to refuel when I took my R&R in Sydney the summer of 1969. Nice lady in the terminal was giving out coffee and pastries. I asked her why. She said "Every time I see a Yank I think of the Coral Sea."

 

Much better than my answer... but I'm living with just a few tools and relying on pros or my friends who can help. Gary

 

ditto on cutting the ends off and waiting till you have the wheels to size the rear end. It makes good since to put the wheels and tires under the car where you want them and just measure in between.

 

When you reweld the ends on the axle I would attempt to find some one with a fixture to make sure it's straight. In our shop every rear is welded in a fixture to maintain straightness. It doesn't take being a little out of straight to have a bearing eater.

 

The 4 Link I Have has all the brackets already made up the Kit comes from a racing fabrication compony in Australia . I also bought new cups for the diff they are ford Big bearing ends.
Krylon32 Is a fixture the long bit of steel you see welded to the back of a diff that kind of acts as a strap?
The Axels I'm looking at getting come in three different lengths and have an extra long spline so you can cut them to suit your application.
Darwin Is a lovely little place we have just hit the dry season so it's nice a cool at the moment.

 

A Fixture is another name for a Jig, basically holds everything square for welding when shortening the Diff, to my knowledge there isnt one in Darwin