Thread: Narrowing a 9" ford rear end

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I am narrowing a 9" ford housing in my shop. I have borrowed a narrowing jig, and I have all the necessary equipment. I have never done this particular activity before but I won't let that stop me .The jig came with no instructions.
My question is, what is the tolerance for misalignment of the bearing bore in the housing end, both radial and axial. I looked all over the 'net and found nothing. (I know the tolerance isn't 0.00",so it must be something)

Also, I am working with a rear end housing with the old style big,(3.150" OD), bearings and the heavy axle tubes. (1/4" wall)
The size of the housing end requires the end of the axle tube to be counterbored to allow the housing end to be inserted. I guess this isn't a problem with the thinner wall thickness tubes.

Has anyone here had any experience with doing this. The od of the housing end is 2.665 and the ID of the tube is 2.55 or so. It is a seamed tube so it is out of round as well as not concentric with the alignment jig bar. I have a feeling that I am going to be hogging it out to fit with a die grinder to fit but I thought I'd ask here and see if anyone had another suggestion.

One rear end shop told me they cut the insert end off, and just buttweld the end back on when they narrow them. I guess he doesn't realize that is where the seal is supposed to seat. I'm glad I am not taking it there.

Thanks for reading this, Mikey

I don't know what the tolerances are, but they must be somewhat generous cuz a lot of stock rear axles get mildly bent along the way.
Due to jacking in the center etc. and most times bearing life isn't affected to any great degree and there's usually no difficulty in pulling or replacing an axle.

The professionally narrowed rear axle in my 32 is further off as compared to the narrowed axle I did at home for my 31.
The narrowing was done on a frame table, but a flat piece of channel or I-beam would work ok for a base.

Only additional thing needed is a couple of 4" x 1/4" angle brackets drilled to match the axle tubing ends where the axles proper bolt up.
These allow clearance for the punkin and when clamped to the frame table - or other flat surface - assure a 90 degree fit vertically.
the 90 degree horizontal fit can be easily checked with a couple of flat bars and a tape measure.

After things are tacked, measure with a digital level and see how things came out.
Turn the axle housing 90 degrees so you can check the horizontal alignment.
If you measured carefully between the flat bars it should be right on the money.

Checking done with a digital level that's accurate to a few seconds of arc.

You're probably cutting a 61 1/2" wide (measured outer drum to outer drum) axle down to 56" - which is a common width for most hot rod installs.

Cut the axle tubing ends off just inside the factory weld.
Machine the weld off the axle ends and generally clean things up.

Cut the axle tubes to size allowing for the length of the axle ends so as to end up with the width you want.

A little clean up of the axle tube's ID and chamfering the inner edge a touch - a drum sander on a 3/8" drill motor works fine - allows the axle ends to be tapped in with a soft hammer.

Put a fairly good chamfer on the outside edge of the axle tube for good weld penetration.

Align, make four strong tack welds 90 degrees apart.
Complete the weld by welding the area between tacks.
Do the first two welds at 180 degrees to each other, let cool to ambient temp and do the other two welds.

Butt welding the axle tubes probably works ok, but it's better to do it like the factory did.

Factories do things for a reason and if butt welding really was good enough you can bet they'd do it just for the savings in $$.

Thanks C6x, I'm narrowing a 65" hub to hub down to 58". It is going under a 68 Imperial. The use of the angle iron to further steady the housing ends while welding and tacking is a good idea. I didn't think of that.
I have a big cast iron 90* angle plate that I use on my mill that will probably work. I should get myself set up with a piece of "I" beam to do this with also.

During this build I welded the four bar mounts on and the axle tubes pulled some, before I cut the bearing ends off I straightened the housing out so the bearing ends are within .020" of centering on the alignment bar that comes with the narrowing jig. I guess that might be close enough.

When I cut the housing ends off I chucked them in the lathe and went to clean the remnants of tube off and found that the tube end had been bored to fit the housing end with a light press fit. I got into the housing end with my parting tool. I guess the combination of a big bearing and a 1/4" wall thickness tube doesn't allow for a sloppy fit. I'm leaning towards buying some new ends from moser to save myself a little cleanup time on the old ends. This car is 4500# so it will be a little extra peice of mind to have new ends anyway.

The welding prep and procedure as you describe is about how I had thought to do it.

I think I'll ask Moser if they know of a tolerance when I call and order the ends and axles.

Thanks for the reply, Mikey

One thing I forgot to point out was that I tied the axle, axle tube ends and 1/4" angle brackets together with a 5/8" piece of all-thread.

Granted, no big heavy guide rod, but if you're careful and think it through you can get away without using one.

The new alloy Dutchman axles slid right in with no problems.

To get an alignment that is ideal I would recommend making 4 blanks, two of which will have the outside diameter of your axle bearings with 1 1/4 inside dimension and two of which will have the outside diameter of your ring gear or third member bearings, with an inside dimension of 1 1/4 then you can remove the ring gear, install the 2 blanks where the ring gear bearings go, and install the third member and replace the axle bearings with the other two blanks. Next install a piece of cold rolled steel (cold rolled should be within .002 tolerance)the full length of the housing, going thru the blanks. This will give you a true and straight alignment with less chance of getting off center, causing premature axle bearing failure. After completion of welding you can slide your axle bearing fixtures into the axle housing and measure the gap between the axle bearing fixture (or flat) and the axle housing face. The tolerance should be no more than .005 .

Thanks, chickenlegs. In my first post I said that I borrowed a narrowing jig.

It is exactly what you describe. It is installed already using an empty third member that I had hanging around the shop. Before I installed it in the housing the 1 1/4" alignment bar was checked for straightness using a set of V blocks and a dial indicator. The alignment bar was true within .002". I was not happy with the alignment plugs (you called them blanks), that went in the housing ends (they were pretty sloppy from abuse during past uses), so I made a new one that allows both the bearing bore and the flange to seat on the plug. The new plug runs true on the shaft with less than .001" runout. It is also longer than the old plug(s )so it should not be as prone to cock on the shaft.

I called moser engineering and the phone tech guy did not know the misalignment tolerance dimension. He did say they use a 1 3/4" alignment bar and massive fixturing. He said that enabled them to make 1 quick continuous weld all the way around ,and that seemed to keep things straighter than numerous segmented tacks and welds. I'll be TIG welding mine so I can check it as I go and make adjustments as needed.

I have heard from several other folks that when the axle housing is all welded up if you can turn the bar by hand with all 4 plugs in you are good to go.

I will try to keep things within .015 TIR. I noticed that the bar by itself sags from its own weight about .001, so it will be hard to measure to .005.

I found a tech article, (through the HAMB), on the fordmuscle website that went pretty in depth about the procedure and I contacted the author, who straightens and narrows rear end housings as part of his business. He told me .020 was what he shoots for and has no problems.

Here is a link to the article. http://www.fordmuscle.com/archives/2...Inch/index.php

I had to buy a 1 year 15.00 subscription to read the entire 3 page article, It was worth it to me, as the second 2 pages had alot of pics and some pretty good technical writing.

Thanks for reading this,
Mikey

for bearings you want to be on about .001 if you can but no more then .002 thats what i was told at school when i was makeing some bearing press keys all i can say is take your time