Math check for narrowing an Explorer 8.8, real narrow, not the junkyard axle swap narrowing!

[corerftech]

Work and life have prohbited me form spending much of any time on my v8 ranger project. Today was good, I got to mock hang my Explorer 8.8 (31 spline) with the actual tires and wheels. I need to get ride height correct as the truck is getting an MII front end and the ride height must be set at back before crossmemebr can be retrofitted.


Anyway...... with the rear end in front of me and mocked in fully, I saw some really good stuff to save money, time, etc. I am planning to use two Cut to Length axles and convert to a 9 inch Torino bearing housing, deleting the C-clips. I have the ends,, bearings, retainers, etc here...... but measure twice, cut one has kicked in.

As I looked at the whole assembly, I realized that I was in better shape than most 8.8 narrowing projects, labor wise, due to use of new CTL axles. I am looking for someone to do a math check (sanity check) on my numbers for cutting.

The process is not one I have read or seen anywhere. The spring perches stay right where they are. My jaw dropped when I had the epiphany. I am running homebrew Caltracs on factory springs with KrySlur sliders instead of shackles. I dont like KrySlur motors.

My Tires mounted to axle (total Overall Width) is 71 inches and that is generous. That measurement will ensure a safety margin for the 275/60R15's (street tires) mounted on the 15x7, ZERO offset wheels. I also have the same wheels in 15x8, ZERO offset, for the drag radials, also M&H 275/60R15. So the OAL (width) will not change regardless of my activities.

The bed width, stock 87 short bed, is a generous 64 inches. That number is also guarded to ensure I can't cut a tire sidewall ever. FYI, the fender tubs will be removed completely so I just need the WIDTH to be right. Ill fab tubs to fill the holes when bed is finally reattached.

So 71- 64= 7 inches to be removed from the axle width in total.
I need to center the pinion as the stock fuel tank is gone via this process as well.
As I have read (not measured), a Stock late model (2001) Explorer 8.8 disc axle pinion is offset by 2 inches to the right. So the pinion/axle must shift two inches left to make it centered.

Therefore I must in basic form, remove 7 inches "unequally" from the axle.
Wheel/tire outside dimensions need 7 inches split equally. So each tire must move 3.5 inches inward.
By shoving the entire axle (theoretically) two inches left, I still need an added 1.5 inches removed in length on the right side. Shortening the right axle 1.5 inches is needed. That accomodates the right side of the rear end.

By moving the entire axle left, I then have 2 inches of extra overhang on the left side. So the left tire which needed a reciprocal 3.5 inches inward movement, now needs 5.5 inches (3.5 + 2 = 5.5 inches).
Therefore by removing 5.5 inches from the left axle will bring the outside edge of the tire inward and correct the pinion centerline offset for me simultaneously.

Where it gets interesting is Im cheap. Id rather not cut off the spring perches. Becasue Im using custom axles on both sides, I can on the right side, section the 1 inch out from behind the perch and leave perch at factory angle and attached. Likewise on the left side, I can section 5.5 inches from behind that perch and leave it attached.

As long as I section each side at precisely the same point with reference to the bearing/backing plate flange, then the spring perches will be symmetrcal to the tire/wheel mounting surface and be symmetrical overall.

Now that creates a mess of the perch spacing. But my perches have moved inward exactly 3.5 inches on the right, 3.5 inches on the left when all cuts and shifts are made. Fortunately I have to move my leaf springs inward as well and my intentions were to fab mounts to hang them directly under the frame rails. Since the LEAF SPRINGS are the wildcard, by altering the perches to a GIVEN width (could be very arbitrary and still work), then installing leafs at that new spacing makes the leafs fit regardless. If I was NOT moving the leafs (I have to, they are very much in the way), Id be screwed. That is the magic combo. Moving the leafs in conjunciton with custom axles.

So the math is I have a 71 inch tire to tire, needs to fit into a 64 inch wheel well opening so as to not shred the side of the tire and not have to bend any part of the bed metal. Narrow rear 7 inches total. Move right and left 3.5 inch inward. Move right by shifting entire housing 2 inch and center the pinion, cut an added 1.5 to make the full 3.5 adjust. Left side, cut 5.5 from housing, thereby relieveing the 2 inch from centering pinion, 3.5 inch tire relief.

Does anyone else follow that logic?

I have Torino ends for big bearings to add to the equation. I dont think that will be a bother as long as they remaing symmetrically installed/welded.

Factory perch width: 38.5
New width: 31.5

RH axle stock: 27.625
LH axle stock: 30.500
Total axles: 58.125

New RH: 26.125 (1.5 shorter)
New LH: 25.000 (5.5 shorter)
New Total axles: 51.125

58.125-51.125= 7.000 inches.

So I have cross checked the math at the housing an axle dimensions and they correlate.

Can someone give me a sanity check on the math? Did I miss something??

I used Rangerstation axle data for the calculations.

Ill write this up when I execute the work.

Thanks in advance

 

[SenorNoob]

Too much. I can't focus. Maybe draw it out?

Wish I were more help.

 

[corerftech]

picture attached

 

[sgtsandman]

You might need one of the racing guys to chime in on this. @Maritime Drag Racing any thoughts? I know there is another one but the name escapes me.

 

[franklin2]

I would do it one step at a time. Move the springs first. Then cut the spring mounts off, set the axle in place with it 2 inches to one side to center the pumpkin, and then you can mark where the spring perches will go. While you are there you can measure how far out the axle flange is and how much needs to be cut off each side.

I am assuming you will section the axle on the outer ends beyond the spring?

 

[don4331]

Work and life have prohbited me form spending much of any time on my v8 ranger project. Today was good, I got to mock hang my Explorer 8.8 (31 spline) with the actual tires and wheels. I need to get ride height correct as the truck is getting an MII front end and the ride height must be set at back before crossmember can be retrofitted.


Anyway...... with the rear end in front of me and mocked in fully, I saw some really good stuff to save money, time, etc. I am planning to use two Cut to Length axles and convert to a 9 inch Torino bearing housing, deleting the C-clips. I have the ends,, bearings, retainers, etc here...... but measure twice, cut one has kicked in.

As I looked at the whole assembly, I realized that I was in better shape than most 8.8 narrowing projects, labor wise, due to use of new CTL axles. I am looking for someone to do a math check (sanity check) on my numbers for cutting.

The process is not one I have read or seen anywhere. The spring perches stay right where they are. My jaw dropped when I had the epiphany. I am running homebrew Caltracs on factory springs with KrySlur sliders instead of shackles. I dont like KrySlur motors.

My Tires mounted to axle (total Overall Width) is 71 inches and that is generous. That measurement will ensure a safety margin for the 275/60R15's (street tires) mounted on the 15x7, ZERO offset wheels. I also have the same wheels in 15x8, ZERO offset, for the drag radials, also M&H 275/60R15. So the OAL (width) will not change regardless of my activities.

The bed width, stock 87 short bed, is a generous 64 inches. That number is also guarded to ensure I can't cut a tire sidewall ever. FYI, the fender tubs will be removed completely so I just need the WIDTH to be right. Ill fab tubs to fill the holes when bed is finally reattached.

Can someone give me a sanity check on the math? Did I miss something??

OK before we get into the math, something to note and couple questions. This is Ford, so nothing is easy.

Note:

Explorer solid rear axles come in 3 flavours - chocolate, strawberry and vanilla. Sorry, drum brake ('93-4), and disc brakes with 2 different offsets('95-'00 and '01-05).​

RH axles (Information is from Dutchman axles)​

'93-4 = 30-13/16"​

'95-00 = 30-1/2" (E5TZ-4234-B)​

'01-05 = 30-11/16" (F1TZ-4234-B) (Explorer Sport and Sport Trac)​

LH axles​

'93-4 = 27-11/16"​

'95-00 = 27-5/8" (E5TZ-4234-A)​

'01-02 = 27-13/16" (F1TZ-4234-A) (Explorer Sport and Sport Trac)​

Adding in '98-09 Ranger​

RH 27-1/4" ('93-7 Rangers axle shaft 27-1/8")​

LH 30-1/4"​

​

99% of users on forum here are just bolting axle in so actual axle shaft lengths don't matter, but if you are narrowing an axle and there is 3/8" difference to start with could be...embarrassing.​

​

Frame width per Ford Body Builder Manual is supposed to be 32.835" (Close enough to 32-7/8" for practical purposes)
According to the aforementioned manual Ranger spring perches are 986mm (38-11/16)", Explorer ones are wider (function of wider frame/spring under for the SUV). So, don't use 38-1/2" as gospel.
Explorer axle centerline offset from body centerline, aka dimension w707, is 30mm(1-3/16") FBBM shows axle as being offset to passengers for Ranger, but does give the value for the dimension (but quick review of the numbers says it should be much closer to 1-1/4" than 2 found in table...)

​

Questions:

a. Aren't you cutting off the 8.8 axle ends, and replacing them with the 9" one, and won't this affect your calculations? Do the Explorer caliper mounts bolt to Torino axle ends? Or are you changing to completely different brake set up which will affect axle tube length??​

b. Are you factoring in the stock engine & transmission was offset 2" to right (to counterbalance driver/fuel tank)? I'm guessing your new engine/transmission combo is closer to centered? Is that going to make your truck driver's side heavy??​

​

To the math: (using your numbers)

71" outside to outside = 35-1/2" to centerline; pinion would be 37-1/2", 33-1/2" (assuming 2" offset to passenger's side)​

Cut 4" off driver's side, to center pinion (33-1/2", 33-1/2") = 67" total width; 3" still too wide​

Cut additional 1-1/2" off driver's (5-1/2" total) and 1-1/2" off passenger's: 32", 32" = 64" total​

​

RH axle stock 27-5/8"
RH axle shorted (27-5/8" - 1-1/2" aka 1-4/8" = 26-1/8")

LH axle stock 30-1/2" (Dutchman axles again)
LH axle shorted (30-1/2" - 5-1/2" = 25")

Did I help you or add to confusion?

 

[corerftech]

Don, thanks for the reply.

Not in a particular order:

Yes torino F9 inch big bearing ends being added, their offset/change in housing length per side would be factored into the shortening/removal of housing material. Its moot. Washes out in the shortening process and isnt worthy of factoring in this case, but worth mentioning... yes.

The specs from Dutchman I had not seen and actually is corroborated by my static "real rear end" measurements of my donor. My tape measures shows not 2 inch pinion offset but something different, a fractional number.

BUT:::: Pinion offset is not chassis centerline offset, it is the offset from the center of the carrier as I understand. Hence the difference in my REAL measurements. I believe your Ford builder data is referencing the centerline of chassis and pinion offset to it.


So before I tackle your measurements, it appears mine are jaded due to my offset discrepancies but not in theory/application. I’ll add that you calculated identical axle lengths after housing narrowing. 26.125 and 25.000

That gets me to a point of ordering raw axles with a CTL max of 27.000. As long as neither side is longer than 27 and more than about 22, I’m good to order.

Ill digest more later. I will go tear the rear end donor apart and get real axle length measurements to confirm donor offsets.
I pulled this rear from a 97-01 Explorer, its is factory disc, yes the Torino ends actually match the EXP brakes and it is the GOTO disc brake upgrade for all narrowed 8.8s using F9 axles and big bearings. Its a recipe. I had to ask Quick Performance for some help to get that fact!

Be back in a few hours!

Happy Easter!

 

[don4331]

I assume (and I know what ass u me is) that the spring perch to axle shaft end is equal on both sides, which would make chassis centerline to pinion and axle centerline to pinion offset the same. But I have to admit I've never measured that.

Yes, if you are cutting your own axles, 27" CTL axles will be fine.

You confused me there as Torino ends don't match EXP brakes, but then my wife's sister had an '83 EXP as graduation gift. And I know about GTOs, as a friend had a '69 in high school, but I've never heard of GOTOs.

 

[Josh B]

You should draw a picture and put the measurements on it and add it up
Make a back view or a top view, whatever you like

 

[corerftech]

Torino ends ONLY match 97-01 Explorer 5.0, 31 spline rear ends.
It is a unique situation.
All conversation on this subject pertains only to the 97-01 5.0L explorer rear end. If comparing to any other explorer rear, it’s an error.

Strange, QP, Moser all sell late Torino new model ends specifically for explorer brakes, plus they sell performance brakes for the same (drag sets, etc).
I was confused for a bit until Mode and Quick both offered me the “hey man, they fit like peas and carrots, that’s the hot ticket!” I then went down road for changing to the Tornio ends to delete the c-clips and get more NHRA rule conformity, plus all the benefits. And it’s cheap!!

Not quite as slick as a big 9 inch but nearly, and not nearly the weight.

yes on perches and equidistant positions.

Usually when narrowing an 8.8, you don’t have more than one weld seam and only one side. In my case, very narrow is needed to two seams. Then the bearing housings, that make two on each side. At that point I figured I could preserve the perches in full, not weakening the housing further, then play mathematician with sectioning to put everything where it needs to be. And the 9 inch axles are forgiving by at least a 1/4 inch in length. So as long as housing is under the maximum on the long side and symmetrical, I can’t lose. I may even get the perches clocked separate from the housings to set pinion angle correct for the caltracs to be deployed without the use of shims——-

Thank you for the input and data Don.

:: GOTO
Go to

the plan to go to
The parts to go to.

 

[Josh B]

What's wrong with "C' clips?

 

[alwaysFlOoReD]

What's wrong with "C' clips?

No good if you're racing on a sanctioned track. If the axle breaks the wheel can come off. The other styles like 9" use bearing retainers at the wheel side of the axle so much less likely to lose a wheel.