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Rear axle choices Ford 9" or 8.8" or other? (2008-2022 bump)

Captain Bondo said:
:wtf: Did you get that from google or something? No offence, but you obviously aren't speaking from experience. Either that or you suck at narrowing rear ends.

With no bearing installed in the end housing you can easily verify if the housing is aligned on-axis to the splines by installing an axle and moving it in a circle. It should not be able to touch the bearing housing at it's extreme limits, and clearance should be the same all around. Assuming the axle is straight, and spline wear is even, this is foolproof.

If the axle is not straight or the spline wear is uneven, then you're screwed anyways.

Getting the end housings square is not rocket science.

You can easily check runout at the housing end with a dial indicator by mounting the axle on a couple of stands with the stands placed near the pumpkin and rotating the pumpkin.

I did all of these checks when I narrowed mine and guess what? It was straight. I actually expected that I'd need to straighten it.

All of the whining and naysaying in this thread is pretty weak. BBQ, bigbegum, and myself have all done this and our diffs check out straight. If you haven't done it or can't do it, don't just say it can't be done.

And suggesting using a domestic ford rear end is an "expensive" way to go about getting a strong rear end is one of the goofier things John V has ever come up with. Obviously you can buy some expensive parts for them, but when stock explorer rear ends are holding 500hp all day long... one should consider reality.
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That comes from experience working in a shop that built more than 250 9" rears last year alone for Cup Cars, not to mention those for all sorts of other racecars, including narrowing quite a few stock housings for drag cars. Sure it may not be drastically off, but I'd be willing to bet that its not nearly as 'perfect' as you're proclaiming. It only takes .010" or less to have a profound difference at the contact patch.

I never said it wouldn't work, I just said it wouldn't be quite right. That's your deal though, I'm thinking much more likely you got lucky :e-shrug:
 
John V said:
It was a suggestion of something for the real world where people don't have to narrow and but custom axles, and can do a lot of the work themselves.

But it isn't the received dogma so I'll let it drop, obviously everybody needs Ford 8.8 units.:roll:

As for weight I believe I read or somebody has previously said it was in the neighborhood of 20lbs more.

Just as a side note doesn't anybody else find it odd how the measurement is always quoted as "31 splines" or "35 splines."
I checked my soooooper accurate very-nears and I only had a choice of English or metric, could find the button to convert diameters into "splines".

And like so much accepted--but never explored dogma, doesn't seem like anybody like to state what DIAMETER people are starting from and what they are wishing for in any of the 2 major measuring systems used in the world.
Is it that everybody knows how many mm or inches all the axles in discussion are already and I'm just too far behind the times?
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standards.....

as the spline count goes up, the diameter HAS to go up due to the diametrical pitch being used as a standard to ensure everyone is on the same page and parts interchange

that being said, someone "could" taper the axle down in diameter too much, but I don't think that is common practice...
 
mAydAy said:
That comes from experience working in a shop that built more than 250 9" rears last year alone for Cup Cars, not to mention those for all sorts of other racecars, including narrowing quite a few stock housings for drag cars. Sure it may not be drastically off, but I'd be willing to bet that its not nearly as 'perfect' as you're proclaiming. It only takes .010" or less to have a profound difference at the contact patch.

I never said it wouldn't work, I just said it wouldn't be quite right. That's your deal though, I'm thinking much more likely you got lucky :e-shrug:
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:nod:
 
I took all of the measurements at least a year ago and posted most of 'em. :e-shrug:

What are we actually debating that calls for measurements? Maybe it's me that's missing the point?

If we're trying to get a feel for axle strength, the off-road guys have actually tested most of the major axle sizes to failure, so there is even better info than just dimensions out there, there are actual torque-to-fail test results floating around.

Mayday: Call it luck if you want- if you want decide it was a fluke rather than accept that maybe I did it right, that's fine. If it was 10 thou off I'd cut it off and try again. 10 thou at the 60mm flange is obviously a lot more than that multiplied over a 25" diameter wheel/tire.

I could to another one the same way tomorrow, and it would be the same. Not "luck".
 
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Captain Bondo said:
I took all of the measurements at least a year ago and posted most of 'em. :e-shrug:

What are we actually debating that calls for measurements? Maybe it's me that's missing the point?

If we're trying to get a feel for axle strength, the off-road guys have actually tested most of the major axle sizes to failure, so there is even better info than just dimensions out there, there are actual torque-to-fail test results floating around.
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I don't think anyone is trying to call you call out....he is just stating that for the majority of the population, this is not a mod that should be attepted in thier garage or carport.

You make it sound easier than it really is, of course I would hope that anyone contemplating such a modification would have some decent tools and skills and didn't just pick up thier 1st 110v welder from Home Depot a week before narrowing thier own rear axle assembly :)
 
Captain Bondo said:
I took all of the measurements at least a year ago and posted most of 'em. :e-shrug:

What are we actually debating that calls for measurements? Maybe it's me that's missing the point?

If we're trying to get a feel for axle strength, the off-road guys have actually tested most of the major axle sizes to failure, so there is even better info than just dimensions out there, there are actual torque-to-fail test results floating around.
Click to expand...
I was merely trying to dissuade the average member from attempting to shorten a rear on their own due to the possibly expensive repercussions.

Definitely look up at the offroad guys for axles, they are probably the toughest on them and put the most time into researching them. There are some offroad axles sold that are guaranteed bulletproof and they will replace them for free if you can break them, not sure how they would take to putting them in street cars but I bet they'd be pretty confident in them.

There should be semi-floaters out there available for drag cars, and most roundy-round and road course cars will have full floaters in them, so there's plenty of strong full floater axle assemblies around too.
 
Mueller said:
standards.....

as the spline count goes up, the diameter HAS to go up due to the diametrical pitch being used as a standard to ensure everyone is on the same page and parts interchange

that being said, someone "could" taper the axle down in diameter too much, but I don't think that is common practice...
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I hain't assumin' nuthin.
the ultimate question really is the spline Minor diameter but since there is no one set spline in the world the simplest thing seems to me to measure the OD, and say what the PA is.
Now mark being a real troublemaker did just that.
And he did it in the system invented by those Gallic bastids and the one based on the thumb of a mythological King somewhere..

Now I like the 'Systeme Metrique' so I just measured the Toyota thing and it is
32.65mm.

Now I don't have a Volvo axle laying by the desk here but my memory says it is the same as 99-900 Saabs or about 29mm

So clearly MarkieBBQ is the man, his axles are a massive 1,2mm bigger.

Those Toyota guys are all limpwristed poofs anyway!!!

Once again, regardless of all else BIGGER is STILL BETTER!
 
John V said:
I hain't assumin' nuthin.
the ultimate question really is the spline Minor diameter but since there is no one set spline in the world the simplest thing seems to me to measure the OD, and say what the PA is.
Now mark being a real troublemaker did just that.
And he did it in the system invented by those Gallic bastids and the one based on the thumb of a mythological King somewhere..

Now I like the 'Systeme Metrique' so I just measured the Toyota thing and it is
32.65mm.

Now I don't have a Volvo axle laying by the desk here but my memory says it is the same as 99-900 Saabs or about 29mm

So clearly MarkieBBQ is the man, his axles are a massive 1,2mm bigger.

Those Toyota guys are all limpwristed poofs anyway!!!

Once again, regardless of all else BIGGER is STILL BETTER!
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again, standards, with the standard 24 pitch used, the minor diameter will be a percentage of the major diamter, just like your nuts and bolts....if a manfucture made a 31 spline count axle have a smaller minor diameter than another manufactures 30 spline count axle, they did not follow the standards and yes is would/could be weaker
 
Mueller said:
again, standards, with the standard 24 pitch used,
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Standards? StaaaaaaAAANDARDS????!!!!!
We dun got no standards.
We dun need no stinkin standards!!!

Well ya know since i dun't works on 'Merikanski stuff and i see 30 and 545 and square root standards and different spline counts for You're a peein' and Japonaise shafts and of course neither of those usually work in 'Merikanskij schtuff, I diodn't stink it was useful when talking about US, Swedish and Japanese axles to presume they all used putative US standards.

:neener::neener::neener::neener::neener::neener::neener::neener:
 
Mueller said:
again, standards, with the standard 24 pitch used, the minor diameter will be a percentage of the major diamter, just like your nuts and bolts....if a manfucture made a 31 spline count axle have a smaller minor diameter than another manufactures 30 spline count axle, they did not follow the standards and yes is would/could be weaker
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That's my understanding as well. Couple this with the fact that we are talking about torsional strength, and a 1.2mm difference is more than it seems at a glance, like a 25mm swaybar vs a 23mm swaybar - as a percentage there's a much larger difference there than the diameter would suggest because it is not a linear relationship.


True enough that people shouldn't just pull out their harbor freight fluxcore welders and start building diffs- I really hope that's obvious but maybe not. But- the context of this thread (at least initially) is primarily geared towards cars in the 500+hp range, and IMO most folks building cars to that level, either know enough to do it right, or know enough to have someone else do it right. Hopefully none of them are dumb enough to think that welding and aligning suspension compnents correctly is unnecessary.

But maybe they do and if so thanks for the reminder. Hopefully I keep getting lucky when I build mine. :roll:
 
John V said:
Standards? StaaaaaaAAANDARDS????!!!!!
We dun got no standards.
We dun need no stinkin standards!!!

Well ya know since i dun't works on 'Merikanski stuff and i see 30 and 545 and square root standards and different spline counts for You're a peein' and Japonaise shafts and of course neither of those usually work in 'Merikanskij schtuff, I diodn't stink it was useful when talking about US, Swedish and Japanese axles to presume they all used putative US standards.

:neener::neener::neener::neener::neener::neener::neener::neener:
Click to expand...

good chance the rear end stuff for Toyotas is "based" on common US stuff so as to not deviate too far away....as for Swedish standards, same as US standard for this stuff :)
 
mAydAy said:
I was merely trying to dissuade the average member from attempting to shorten a rear on their own due to the possibly expensive repercussions.

Definitely look up at the offroad guys for axles, they are probably the toughest on them and put the most time into researching them. There are some offroad axles sold that are guaranteed bulletproof and they will replace them for free if you can break them, not sure how they would take to putting them in street cars but I bet they'd be pretty confident in them.

There should be semi-floaters out there available for drag cars, and most roundy-round and road course cars will have full floaters in them, so there's plenty of strong full floater axle assemblies around too.
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i'm still trying to figure out why if you work at such a place you have not made ready to bolt-in rear end assemblies for us !!! :)
 
Mueller said:
i'm still trying to figure out why if you work at such a place you have not made ready to bolt-in rear end assemblies for us !!! :)
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Haha I thought about it when I worked there (just returned back to school after 1.5 years of building chassis for them), there was a few problems, namely the biggest one $$ wise I saw was getting hubs made. We stocked them in 5x5 and 5x4.5, but it'd be such a limited run for 5x108 that it wouldn't be cost effective, and a lot of people wouldn't like having mismatched bolt patterns, and making front 5x4.5 hubs would then bump costs up even higher. Its hard to market something thats very all or nothing -- as in you buy this rear and these front suspension parts, or you get all sortsa mismatched parts or nothing. Scalability, if you will, is pretty important in suspension systems, since only a small portion of your customer base will be looking to buy "Everything at once".

If I was to do an extreme 240 (or 740 for that matter) I'd do like Bondo talked about converting the rear to a 4 link (Would be pretty easy really) and throw in a 9", and convert all the running gear to standard roundy-round late model parts because of how cheap and available they are. The standard for brakes are 1.25"x11.75" (there are larger options) which are cheap and fit under 15" wheels (since they all run 15" steel wheels, there has been tons of developments in these systems, most notably are the pad compounds they have for track use. Pad choices are endless and not too pricey, and rotors, hell, you can find them for under $40 per (and they're the two piece style). The hardest part would be likely having to develop some sort of front hubs or somehow adapt some sort of hubs to the front that will work, but I have a few ideas on that too.

If there's enough interest in the future, some more development is a possibility if there's someone who wanted to blaze down that path I'd be more than willing to work on some stuff, it'd be a lot easier than people think to do it all and do it right. The problem is that this is a hard market to enter, and it certainly wouldn't be worth it for me to attempt to compete with Lawrence or Bne, when they barely have any demand for their parts. It'd be worthwhile for a few people wanting something one off thats top notch, reliable and cheap to maintain, but I don't think I'd ever try to market it in any numbers because of the demand in this market for anything over $20.
 
C- clip eliminators are required for drag racing after certain ET's are obtained too,besides any mods worth doing are worth doing right,RIGHT? Do you really want to depend on your brake rotor/calipers when the axle breaks, What if it cuts a brake line, and now you have broke axle and dying brakes? Could get HAIRY! Always remember, In Racing, whatever can go wrong, probably will,sooner or later. Also , RACING!! because basketball,golf,football and bowling,only take one ball!! I would definately use the C-clip eliminatators for ANY type of racing!!
 
smokeyfan1000 said:
C- clip eliminators are required for drag racing after certain ET's are obtained too,besides any mods worth doing are worth doing right,RIGHT? Do you really want to depend on your brake rotor/calipers when the axle breaks, What if it cuts a brake line, and now you have broke axle and dying brakes? Could get HAIRY! Always remember, In Racing, whatever can go wrong, probably will,sooner or later. Also , RACING!! because basketball,golf,football and bowling,only take one ball!! I would definately use the C-clip eliminatators for ANY type of racing!!
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C clip eliminators are not required at any ET that many on here are going to achieve. Besides, if you have a C clip failure (hardly an every day occurrance) then you'll be relying on a 1/2 inch thick bit of steel to stop the axle falling out whilst being clamped by the now pressurised caliper to keep everything in line.

I'm no expert but as I understand it that rule was brought in in the days of drum braked 8.8"'s, not disc braked. I've seen FWD cars suffer complete bearing collapse so that the disc and caliper are the only things holding that wheel station together. Yet despite having to suffer turning forces in addition to all those a rear axle would have to suffer, they stay in place.

Before you go spouting internet hearsay I suggest you mount up a caliper and disc on an 8.8" axle, then apply as much force as is needed to break the ears off the caliper using a bar that is attached to the centre of the axle and terminates no further than 15" from that centreline (because most people running slicks bigger than 30" will be on a 9"). On second thoughts, fill your boots- go do it with an 18" bar (36" slick).

Be sure to use some reliable equipment to see just how much force is required to break everything off so the axle can roam free, won't you?

I think you'll be surprised.
 
Regarding strength increase vs diameter:

tau = 2T/pi*r^3

tau is shear stress, T is torque, r is radius

Assume that tau_max is constant. Allowable tau_max actually depends on materials, so in this case, it's not actually correct, but lacking real data on the materials used in each of these shafts, we'll assume that it is constant.

Solve for T/tau.

T/tau = pi*r^3/2

This gives us a ratio of torque to shear stress.

d...........r............T/tau......factor
29.........14.5........4788.77..1
32.65.....16.33......6834.07..1.43
33.8.......16.9.......7581.93..1.58

So an increase from 29mm to 32.65mm gives a 43% increase is torsional strength, and going from 29mm to 33.8mm give a 58% increase in strength.

Not shown, but going from 32.65 mm to 33.8mm gives an 11% increase in torsional strength.

Again, this is based on identical materials, which is not actually correct.
 
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I like the 8.8 because I already had Mustang wheels. The cobra clutch pack I put in the Ford Traction Lok works great and leaves 2 black stripes, it almost feels like a weldy but it goes around corners.
 
VB242 said:
I like the 8.8 because I already had Mustang wheels. The cobra clutch pack I put in the Ford Traction Lok works great and leaves 2 black stripes, it almost feels like a weldy but it goes around corners.
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So.... What year Explorer did you get your rear from?
 
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