Shortening a Ford 9 inch - questions.

[maddog]

I have stripped down my 9 inch rearend and am thinking about shortening it.

I have a couple questions.
Both axles are the same legnth yet the center section is not in the center of the housing. I'm sure this is completly normal, but here is my question.

The housing is about 2 inches too long. Can I shorten just one side, the long side, and just one axle?

This would put the center housing in the center of the car. (yes the driveshaft would still be off center because the pinion is off to the right side of the center section)

Thanks

 

[chopper tom]

ive been wandering the same thing ?

 

[maddog]

Just wait.
I predict there will be an answer to the question of "the lopsided Ford 9 inch rearend"
We couldnt be the only ones that have pondered this delema.

 

[Bonehead]

Better to keep things centered, but you actually could do it that way. Years ago I ran a double transfer case in a 4x4, the output shaft was about 6 inches off center, but the drive shaft was still several feet long. So it ran at two angles instead of the normal one.
That said, if you could find or trade for a more narrow 9 inch you would be better off. Keep in mind that early Ford Broncos have a much more narrow rear than a pickup, and some cars were even more narrow.

Narrowing a rear is not hard but it requires a jig. Then, having axle shafts made.

 

[Gastrick]

I've narrowed a few nine inch Ford rears. Some people, such as those with T Buckets where the rear is exposed, like a centered housing. So yes it can be done that way. I prefer a centered pinion.

I'm just a backyard garage hack but this is how I do it. I'm sure others will have more to add as I'm not a pro but I do narrow my own rears and build my on chassis most of the time. Hope this helps. This basic guide is specific to the 9 inch Ford.

1. Determine the total width of the rear by placing the wheels/tires in their desired location without a rear end in the vehicle. Measure the distance between the wheel mounting surfaces. This will determine the total rear width including axles.

2. If your donor rear is assembled, measure the distance that the axle prodrudes from the end of the axle housing, including the thickness of the brake drum or disk. On a nine inch Ford, this measurement is typically in the area of 2.5 inches per side, for a total of 5 approximately inches.

3. Subract the axle protrusion measurement from your total wheel mounting surface to wheel mounting surface measurement, and this will give you the desired housing width.

4. Remove the housing ends from the housing, and cut the tubes to the desired measurement, and weld the housing ends back on. Unfortunatly, to complete this step properly, you will need a housing end jig or in all likelyhood, the housing ends will not be perfectly alligned with the center section. This will eventually lead to axle, bearing, or rear failure. I have a jig that I use.

5. Assuming that you are centering the pinion and not the housing in the chassis, Here is how you can determine axle length. Use the total mounting surface to mounting surface measurement and subtract one inch from it. The one inch is for space between the axles when installed in the rear housing. Then divide that number by two. Add 2 inches to that measurement and that will be the length of the axle for the long side. Subtract two incesand that will be the measurement for the short axle. This is for a 9 inch Ford.

EXAMPLE:

Total width wheel to wheel = 49 inches
minus 1 inch = 48 inches
Divide by 2 = 24 inches
Add 2 inches for long axle = 26 inches (long side axle length)
Subtract 2 inches for short = 22 inches (short side axle length)

I then order the axles from an aftermarket company based upon my measurements.

6. Install suspension mounting brackets, install completed unit, and burn rubber.

 

[maddog]

Thanks everyone.
A couple more questions.

Is it better to center the pinion rather than the housing? Why?

I read about the jig for shortening the tube once. Is it 4 machined aluminum donuts that replace the 4 bearings and a straight rod that runs through them? Did I miss something? That would be easy to make.

Does anyone know what passenger cars used a 31 spline axle? I understand that I could possibly find a shorter axle from a shorter stock rearend.

I told you Chopper Tom, ya dont have to wait long around here.

 

[donsrods]

I honestly have never been brave enough to narrow a rear end, but to answer your one question Maddog, the reason it may be better to center the pinion than the housing is that the driveshaft ends up more centered in the car, allowing a straight shot from the tranny tailshaft.

Those doughnuts you are refering to are sort of a "go, no go" alignment tool. If the housing warps during welding the shaft of the tool won't go straight in easily. You do various things to straighten it so it will go in like heating and bending it in a press.

BTW, if you only have to lose a couple of inches, you can do that with reverse offset wheels too. My '27 has a 9 incher that is too wide, so I ordered deep offset wheels for the back and it made it ok.

Don

 

[Bonehead]

I still say Ford Bronco is your first check. 1966-1977. you will find more 31 spline axle there, the biggest question is width. As far as cars look for the biggest heavy cars, like a lincoln, or LTD.

 

[Gastrick]

I read about the jig for shortening the tube once. Is it 4 machined aluminum donuts that replace the 4 bearings and a straight rod that runs through them? Did I miss something? That would be easy to make.

That's about it Maddog. Just make sure that the straight bar is true if you are going to make your own jig. A solid bar is best. And machine a shoulder on the ends for your bar for your doughnuts to rest on. Drill and tap the ends of the bar and bolt your doughnuts to the ends of the bar so that there is no movement when in use.

I'd snap you off a few pics of mine but it's on loan to a friend. When I get it back, I'll take some detailed pics for ya.

You will need to shell a center section and bolt a pair of doughnuts (bearing simulators) where the bearings are usually installed. Then install the center section in the housing and slide the bar through it. You can then install your outer bearing simulators on the ends of the bar with the housing ends. Don't be surprised if the axle tubes are off, but don't worry about that. Weld the ends on the tubes in alignment with the bearings and all will be well.

The only other item that you will need is a gauge that bolts to the center section that simulates pinion center. You can measure off of this gauge to the ends of the housing during the fab process to ensure that you are making the housing the correct width. I made my own

 

[chopper tom]

ive narrowed a few chevys and a 9'' ford .I done the 9 out of a race car and if i had 'nt used a jig it would have been of 1/2'' off on each side. i'm a ferm beleiver in jigs [that rear was punished hard on the strip before i cut it].
I hate to admite it but i did string line a chevy before and it worked great ,he drags it and drives it on the street ,so it's not rocket science as long as everything is true in the end.
the 9'' jig i borrowed was made from a raceing go cart axle [hollow,tempered] and it was perfectly strait

 

[Bonehead]

Here is one I cut, afraid i didn't use a jig though.

 

[maddog]

Here is one I cut, afraid i didn't use a jig though.

THATS THE ONE, BONEHEAD. I NEED IT, SPRINGS AND ALL. SELL IT TO ME.

(now I'm gonna find out whats more expensive, art or car parts)

 

[Gastrick]

(now I'm gonna find out whats more expensive, art or car parts)

Car parts made into art are more expensive than both

 

[24dodge]

I cheated , i had a guy in Colorado fab me one......and yes , I remembered to put in the fill and drain plugs

 

[maddog]

I cheated , i had a guy in Colorado fab me one......and yes , I remembered to put in the fill and drain plugs

Thats some good looking stuff, Dodge. What is that in?

 

[24dodge]

my 47 international

 

[Gastrick]

my 47 international

Can we see the see the rest of it? That's a nice setup.

 

[24dodge]

I found these 2 , all my pics of it are huge so I can`t post them

 

[Gastrick]

Cool truck. Do you still have it?

 

[maddog]

I found these 2 , all my pics of it are huge so I can`t post them

I would love to see them, so, try this. Half way down the page is an image resizer. Just click on it and follow the instructions. Its easy to resize any photo then.

http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx

Good luck, we're all counting on you.