Technical Narrowing a 9” Ford- Question?

I was about to shorten a 9” ford axle housing I had laying around for my 37 Chevy coupe build, but I noticed it’s 3-1/4” axle tubes, not 3”. I’m guessing it’s out of a late model F150 or something?


Question:
Is the ID of all 9” ford axle tubes the same? Or would I have to buy new axle flanges to shorten it?

I’m concerned that if I cut the Axle tubes, the axle flange will be too small and I would struggle to keep the two concentric.


If you’re interested, hop on over to my traditional customs build thread “Not your average coupe build” if you want to check it out

https://www.jalopyjournal.com/forum/threads/not-your-average-coupe-build.1048642/


Thanks!






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To do it right you should have an alignment bar and end pucks. That will keep the flamge aligned while you weld. If you don't have an alignment bar, and don't have access to one, and are going to use angle iron, cut the tube inboard a bit and reuse the flanges and just reweld the tube. You may have to straighten it after. Things move around a lot when welding.

 

Are you sure it’s not a truck 9 3/8” Rear end? Look similar, slightly different than a 9 inch. Anyhow, what are the dimensions of the bolt holes and bearing size on the housing ends.

 

Hey mountain, yes I planned to mock something up on my weld table. To keep it square. You’re idea to cut a section out of the axle tube is pretty solid though, eliminates my confusion with the new axle flange.

In an effort to investigate a little further I got a little more confused.

I used a bore gauge to get a rough dimension of the axle tube, but when I compared it to the flange I found the OD of the flange, the land of the flange is 3”, but the ID of the tube is only 2.875”ish.

So is the taper of the axle flange not supposed to completely engage in the axle tube? Or am I missing something










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To bad you're not closer to Buffalo,NY because I just seen a 67-68 mustang 9 inch for sale, probably would've fit without cutting.

 

A mandrel (Alignment bar) with axle pucks is the best way to narrow housing as well as a bare centre with pucks to ensure accuracy, don't forget that axle narrowing guide tool to determine your new axle length

 

Hey badshifter

It could be, I haven’t tried putting a 9” center section in it.

The bearing appears to be 3.125”

And bolt holes match up with my new axle flanges.

3.5” x 3.375












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Apologies for not answering your question directly but here is a possible alternative if your current diff doesnt work out...

If your final desired width is approx 56" here's some info I pulled together about 8.8" diffs. One of the many good things about these is that you use an OEM 'short' axle so its CHEAP to do and you can access a range of ratios, LSD and have drum or disc brakes.

https://www.jalopyjournal.com/forum/threads/8-8-rear-end-for-a-hotrod-info.1203372/

Even if you continue with the 9" there is some useful info about shortening diffs that would be applicable.

 

Hey Pete

Thanks for attaching your thread, that is some good info! If this 9” doesn’t pan out I’ve got a 57 Chevy rear that will probably go in the car. But 8.8 is definitely an economical option.




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The new axle flange does not go inside the tube. It's a flust mount that's why the pucks on the alignment bar position the ends since most of the tubes are not that straight. The bevel on the new end is for the weld

 

Well that makes sense, I think I can consider this question answered then!

Thanks jmountainjr!

 

Big Ford old style, is 3.5” x 2.375” and 3.150” on the bearing.
I’m guessing that’s what you have. Are the axles 31 spline?
Anyhow, it should all work. I would do as was said and cut a section of tube out and and weld back together and not use new axle flanges UNLESS you have the alignment bar. You’ll still obviously have to get axles from Dutchman, Currie, etc.
Also, now is the time to decide if you want the pumpkin centered or the pinion centered. Can’t have both. Sometimes if only one side needs to be narrowed to get what you want/need, you can use two of the short axles and not have to buy new axles.

 

Tje alignment bar is held in position by a stripped center section with pucks replacing the bearings. The axle flanges are aligned by the pucks that position them. Everything is held in alignment while you weld away. The issues might not show up immediately if you shorten a housing without using an alignment bar, but in the vast majority of cases they will show up: axle bearing failure, broken axle, etc. The immediate issue is usually not being able to install the axle into the center section. YMMV.

 

Yup! 2.375”*

I was going to throw in a center section, and try to position a laser level to find/ mark pinion center on the housing. I’ve got to buy axles for it anyways, but I’m hoping I can cut off the same length on each end to make it more straight forward.

 

conceptually, could I throw in a center section, and slide in my axles with bearings and use that to keep everything aligned? I’ve got a 28 spline center section and axles for 1.5” longer housing. Should be enough to engage the bearings about 50% to align it and then weld it.

 

A typical alignment bar is 1.5" OD, polished and ground, and runs straight through the width of the housing. And sometimes things still move around. The slop in the axle spline won't stop the movement much, but it's worth a try. Nothing to lose by trying. After welding and things cool off try removing and installing the axle and you will have a feel if things slip in and out as they should.

 

And if needed, it's not a big deal to straighten the housing.

 

Yeah that was my thought, it would certainly be better than nothing.

I looked up the mitler brothers set, and saw the description. There’s a reason the kits aren’t cheap!




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Do you have a lathe, or a friend with one? The pucks are not hard to make then just buy a bar. Or find someone in your area with an alignment bar.

 

Good info, except the part about welding with the bar in place, I only did that once, took a sledge hammer to drive the bar out. I always align everything and tack weld, mount it in the car, with all brackets tacked on. Weld everything but the ends, check and straighten as needed, weld the ends last.

 

Yeah my friend with a lathe just moved to Colorado lol.


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@Marty Strode .....is spot on about not welding the housing/ends with the bar in place. Using it to align the housing/ends and tacking them before removing the bar is fine...but welding them can/will cause some warpage and bind the bar in the pucks.

In recent months I was doing some of this work (I have a bar and pucks) and used them to first check the housing for straightness. This housing was found bent (note the gap), I straightened it before doing any further work.



This one is an 8.8” and was cold bent back into alignment by using jack stands, a chain and a bottle jack on a frame bench. Actually, I didn’t shorten this one, but did a 9”.

The housing the OP is dealing with is, I believe, a F150 truck housing. I have one like it. Quite stout. 9” housings came in several variations of center housing, axle tubes and ends, depending on application. In any case, it is not a 9 3/8” housing as it lacks the necessary notch in the flange, upper driver’s side, for the ring gear clearance. It wouldn’t matter though, as 9” carriers fit just fine in the notched 9 3/8” housing.

Ray

 

I have narrowed quite a few rear ends and I do own a jig. The amount of very bent housings I have come across is fairly significant. Most come out of pickups due to being overloaded.

 

Mittler Brothers

 

Think I bought mine from Chris Alston many moons ago....Was about 400 bucks back then.

 

Good info on the 9 3/8” housing! Didn’t know the 9” carrier would fit

 

Thanks for the pictures!

 

This is what I use to straighten housings, 12 ton jack with chains, been using it over 40 years. I t will make them talk to you !

 

Yes, everyone is correct about the welding. I didn't go into the details there. I usually tack the flanges and then run 4 beads about an inch long before removing the pucks. After fully welding and cooled, recheck with the pucks to see if any straightening required. Marty's picture showes it all.

 

you can cut the weld that holds the tube into the center of the housing then grind a small bevel on the tube end and press it in you may need to cut a small v notch on the center end where the tube goes in as they are crimped onto the axle tube you can press in as far as you need to for a finished lenght a jig would be the best way but you can get very close watching how the axles slide in prior to welding