Narrowing a rear end

[Bolted to Floor]

To eliminate my tire rub in the back when the trunk I loaded, I am at a point where I buy new rims at a hefty price, work on the rolling the fender lips some more and risk screwing up the paint, or narrow the rear end. Narrowing the rear is the most cost effective method if I can make use of my current axle shafts. I’m looking at taking a ½” on each side and adding back a 1/4” spacer it sets the tire into too far. It should eliminate the tire rub completely.

I pulled the axles out the other night to get some measurement. From the pictures below, it looks like there is about 1-1/8” of spline engaging a factory Ford traction lock unit. Is this the normal spline engagement?  With about 2” of splines available, does anyone see a reason I can’t cut a ½” off the shaft end??

When it comes to the axle shafts, Jegs brand 31 spline shafts, can I cut them with and angle grinder and abrasive cut off wheel? Would it be a best practice to keep the shaft as cool as possible during cutting with a wet rag or something similar?

Driver side


Passenger side
 

                               

Any and all comments appreciated.

[BattlestarGalactic]

I did the exact same thing on my 2 dr Galaxie.  The RR tire would rub if someone sat in the back.  Wasn't an issue with 8" rims, but the 10" rims ballooned the tires out just enough.

I took 1/2" off the passenger side.  Though I do have Moser 31 spline axles, it was no big deal to use a 4 1/2" angle grinder to trim the length down.  Just worked slow and easy and it went right through.  What little heat might build up should not be an issue.

If you want to know the engagement, just run a tape measure down from the center pin to the bearing shoulder on each side and see what it compares to on the axle.  I'm guessing like 1/4" gap(give or take) from axle to center pin.

I put a rear brace on the housing also, since I was welding on it anyway.  Not really needed for street use, but for the $50 brace, why not.

[JamesonRacing]

Any machine shop should be able to cut the axle shafts on a lathe.  The more difficult part is cutting and rewelding the housing ends.  You're probably better off starting with new ends, but getting the cut and keeping the housing straight can be a challenge.  I'd think you'd be money ahead to just order a set of wheels with the back spacing you need.

[JERICOGTX]

Jay knows a thing or two about narrowing a rear end.

[BattlestarGalactic]

The hard part is holding yourself up against the wall like that!!!     

[jayb]

Yes Larry, working while holding the axle housing up against a vertical surface like that is challenging!  Fortunately, my walls are magnetic 

Regarding cutting the axles, I've done that with a chop saw with good success.  Taking 1/2" off each axle should be no problem, in fact when I did the rear end in my 68 Mustang fastback (not the one in the picture), I cut closer to 3/4" off the ends of the axles and re-welded the housing ends.  In the picture Jeff (jericogtx) had lent me his 9" narrowing jig, which is basically a 9" case with some aluminum bushings and a big steel tube.  Two bushings go in the case, the case is installed and the tube slides in and through, and then a bushing goes into the bearing bore of each housing end, then slides onto the tube, to ensure good alignment.  That's a great way to do it, but I'll confess that I've also done without the jig, just by carefully cutting the axle housing and using some angle iron and clamps to align the cut off ends with the rest of the axle tube.  Its important to weld a little button at a time when you get started, switching to opposite sides of the tube and opposite ends of the housing.  When I've done it without the jig I've actually done it with the axles installed, and then checked to make sure the bearing slides freely into the housing end after a bit of the welding is done.  Never had an issue...

[GJCAT427]

Having a machine and fab shop has its rewards. When I did the axle for my Tbolt wagon I made the bushings and bar to align the ends on the housing. It worked very well. I now have guys asking me to narrow the rear ends every so often. As a result I have a series of bushing ends to make life easier on different rears. I have a buddy who wants me to do an 8.8 for his 56 crown Vickie. This may be a little tougher as it has the rear disc with the internal ebrakes. Which in my opinion is a junk design based on the  corvette. 

[BattlestarGalactic]

Agree, I have access to jig set up for housings.  Makes it really easy to adjust things.  It's not really hard, just have to take your time so it doesn't bend real bad.

[Bolted to Floor]

Thanks for the advice guys.

The benefit I see to having a machine shop cut the axles is they should be able to provide a new centering mark on the end. Is there is any added value in keeping that? I do have an angle grinder!! 

New ends are on the list. This was a factory housing for a 68 to 70 Mustang with the tapered down tubes. From what I have found so far, it looks like Currie is one o the few that offers a slip fit into the small tubes with the small bolt pattern. That small bolt pattern is a killer. Still have some calls to make for clarifications.

My welding skills are not up to task for something like this. I have a coworker that has offered to help with that. Neither of us have a narrowing jig either. We had talked through the process using the axle shafts to help align everything. Using new ends that would slip inside the tubing is most appealing, then install the axle shaft with bearings to make sure it all lined up right for tacking in place. For cutting the tubes, I have access to a porta band, angle grinder, and a pipe cutter. I should be able to get a straight cut!!

Those magnetic walls are impressive.

Got to be able to load luggage in the trunk of this thing with no tire rub, we will be driving it to Michigan in June for the Mustang Steve Bash!! Or so the plan goes.   

[JamesonRacing]

Another option if you want a narrowed rear axle is to send the specs of what you want to Quick Performanc and they can build you one at a decent price.  That's what I did on one of my cars. 

https://www.quickperformance.com/QP-Ford-1967-1970-Mustang-9-Inch-Housing_p_34.html

[Bolted to Floor]

That’s not a bad price. Thanks for the link.

[Nightmist66]

Another nice thing about the new housing is that the axle tubes are quite a bit stronger because they are not just butt welded to the center section.

I got a whole new rear setup for mine from Strange. The basic housing package was similar in cost to the QP, IIRC. I opted to go 1/2" narrower each side from stock to fit my tires easier. They didn't charge me for the narrowing, since they were building from scratch. I told them which perches I wanted, where to place them, etc. Since I got the universal perches, I finished boxing them myself. I wanted to get a beefy setup, so I checked almost every upgrade box. I went with 35 spline, HD pro aluminum case, spool, bearing kit, seals, you name it.......

[Posi67]

Just how hefty is the price on new rims? If getting 1/2" more backspacing solves your problem and you actually have the room for the wheel/tire to move inboard that is the easy, no work, no fuss and no questionable results way. Probably not a lot more that what you are considering given you need others to do the cut and weld on the housing. 

[Bolted to Floor]

Yea, I could go hog wild with the options box. 

I like the way these rims look. There are not a lot of inexpensive options that have more than 4-1/2” of back spacing either.

http://www.etmags.com/ac_iii.html

The 17x8 with 5-1/4 back spacing are some of the wheels that I’ve found now $315 plus $$ for caps or spinners and these were $30 cheaper when I looked two months ago!!

From measurements I’ve taken, these would require a spacers on the front so they don’t hit the upper control arm.

It’s amazing how one changes snowballs to effect so much other stuff!!

[Bolted to Floor]

Because I’m using the Mustang Steve brackets for late model brakes, I have to pay attention to the distance from the back side of mounting pad to the back side of the spokes. The calipers stick out past the mounting face on the rotor. Goes back to one thing effects another.