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

fidel sells 27 spline shafts to drop into the volvo rear end that will support 700+ ft-lbs
(simply better metal than volvo used from the factory)
($380ish per set)
combine this with a good solid center diff and the reasons to go away from the volvo unit fade quite quickly
the volvo tubes are thicker than on an 8.8 anyways

Nice work on the failtastic post. :-P The 8.8 axle tubes on the late explorer diffs are 3.25"x0.25" -that would eat a dana 30 axle tube as a light snack in the mid afternoon.

I'll take 31 splines, clutch type posi, good aftermarket, 4x4.5 bolt pattern for the price of a junkyard pull. :e-shrug:
 
Bigbegum has an 8.8 too. Also Bondo. There's some good info on how Bigbegum narrowed his... I think he and Bondo both used Explorer rearends and only narrowed one side 'cause it's offset. This is on two series cars though.

Bigbegum is doing 1.40ish 60foot times on his 8.8 behind a built 383, so they must be pretty tough.

Something to consider on the 9" route is because they have a large pinion offset they have a higher parasitic loss... I can't remember how much exactly, but it's something to consider.

I've got a Chevy truck 12 bolt all ready to get narrowed... gonna run 9" ford axle ends so I don't need to worry about the c-clip thing one way or the other.

M.

EDIT Bondo got in before me!
 
I don't know where you guys have been. But here is the rule straight from the nhra rulebook.

http://www.geocities.com/boosted_eine/nhrarulebook.html

2.3 REAREND

After market axles and axle-retention device mandatory on any car running 10.99 (*6.99) or quicker and any car with locked differential. Cars running 10.99 (*6.99) or quicker that weigh more than 2,000 pounds (907 kg) with independent rear suspension must have swing axle differential replaced with conventional differential housing assembly.
 
Good posts guys. Thanksfor the feedback.
It looks like there is alot of merrit for the 8.8. The removable center section is the best reason to go 9". It makes gear ratio changes easy. But I suppose I won't be changing ratios all that often.

How much weight difference is there in a 9" vs 8.8. They are very close in ring gear dimension. And the simple stamped sheetmetal housings of the 9" seem pretty slimple and light.
 
Nice work on the failtastic post. :-P The 8.8 axle tubes on the late explorer diffs are 3.25"x0.25" -that would eat a dana 30 axle tube as a light snack in the mid afternoon.

I'll take 31 splines, clutch type posi, good aftermarket, 4x4.5 bolt pattern for the price of a junkyard pull. :e-shrug:

that does not make them better, just heavier...of course it is dependant on the application...
 
Nice work on the failtastic post. :-P The 8.8 axle tubes on the late explorer diffs are 3.25"x0.25" -that would eat a dana 30 axle tube as a light snack in the mid afternoon.

I'll take 31 splines, clutch type posi, good aftermarket, 4x4.5 bolt pattern for the price of a junkyard pull. :e-shrug:

So how do you identify the lsd types? Is there a mark on the outside of the axle somewhere? What year explorers roughly?
 
I was one of the guys Bondo talked to about the c-clips :oops:



2007 NHRA rules on C-clips-


All cars, except some ET cars as noted in Class Requirements, must be equipped with a satisfactory means of rear-axle retention; minimum .120-inch (3 mm) aluminum retainer, or .090-inch (2.3 mm) steel bearing retainer is mandatory. Stock ’C’ clip axle retention prohibited as outlined in Class Requirements.

Doesn't mention disc brakes. I was skimming through a couple of things that were saying it's a grey area in the rules. Apparently sometimes eliminators are required with disc brake cars despite the fact that it's exceedingly redundant. I agree with Bondo, but if you're looking build one for a track car it might be worth contacting the sanctioning body to ensure you're complying with the rules.

It's something to think about anyways.

M.
 
I was one of the guys Bondo talked to about the c-clips :oops:



2007 NHRA rules on C-clips-


All cars, except some ET cars as noted in Class Requirements, must be equipped with a satisfactory means of rear-axle retention; minimum .120-inch (3 mm) aluminum retainer, or .090-inch (2.3 mm) steel bearing retainer is mandatory. Stock ?C? clip axle retention prohibited as outlined in Class Requirements.

Doesn't mention disc brakes. I was skimming through a couple of things that were saying it's a grey area in the rules. Apparently sometimes eliminators are required with disc brake cars despite the fact that it's exceedingly redundant. I agree with Bondo, but if you're looking build one for a track car it might be worth contacting the sanctioning body to ensure you're complying with the rules.

It's something to think about anyways.

M.


some of the c-clip eliminator kits come with new bearings and new plates....you just cannot remove the clips and install disc brakes and be done with it...at least that is how I see it...
 
Some interesting reading about the 9" design with regard to strength and parasitic loses. I just lifted this from another forum. So I can't vouch for the source, but it seems legit.
------snip------
I have a Moser 12 bolt, and have always owned 12 bolts, or 8.5 inch 10 bolt rear ends (except for the Dana’s in my trucks). If a 12 bolt would not meet my needs, and so far it has held up to a lot of abuse; then I would replace it with a Dana 60, never a FORD nine inch.

A FORD nine inch takes too much power to turn. I am Scotch. I like my horse power going to the ground, not heating the rear grease in my differential. The strength of a Ford nine inch comes from the fact that two teeth at a time are engaged by lowering the pinion to the bottom of the ring gear. Buy rubbing the pinion past two teeth at a time you double the friction. That is called parasitic loss. A Ford 9" usually has a parasitic rate of about 7% compared to 3% for the Spicer 12 bolt. That is 7% of your flywheel horse power (or what part of it that gets through the tranny which also has parasitic losses of their own) that never sees the tire.

To reduce the parasitic drag of the Hotchkiss nine inch design Strange offers a special aluminum Salisbury bolt in pumpkin that goes into a Ford nine inch housing that uses a Spicer 12 bolt Chevy ring gear and pinion (but it still looks like a Ford rear end).

---- snip------
 
if im cutting a rear end down, im putting the 9" ends on the tube.

I personally don't like the c-clip design for a couple reasons.
1. you can't pull the axles out without removing the center cover to pop the clips off.

2. I always ran the c-clips in my old mustang. And it always bothered me that there was .050-.100" play in the axles if you pushed them in and pulled them out. The cross shaft and C-clips were all fairly loose in all the axles I worked on. Especially with disk brakes, the moving axle can push the pads back into the caliper when you corner and the rotor and axle slide around. They also clunk sometimes. My car was a drum brake rear mustang. So, the brake problem wasn't a problem at all. But the axial play still bothered me.
-- I'll add to that a little after thinking about it --
That is probably one of the reasons for floating calipers. So they can move with the axle. But who wants that crap!
 
that does not make them better, just heavier...of course it is dependant on the application...

It must be friday and everyone is coasting into the weekend. Everyone's IQ seems to be at least 30 points lower than usual. Please tell me you don't actually need me to explain what's better about thicker tubes...

The jury is out on if NHRA will consider discs "a satisfactory means of axle retention". I've never heard of a tech guy ever even asking about c-clips though personally...

Ken,
The is a metal tag on the rear ends attached to the diff cover, there is a number that gives the ratio with a letter in the middle, like a 3.73 is a 3x73 If there is and "L" ther is is a limited slip. Like an 3L73 is a 3.73 with a posi. SOmehting like that. Look for an "L" anyways.

Kepe in mind most c-clip eliminator kits are OUTLAWED for roadracing- they don't like side loads and tend to want to leka diff oil onto your brakes., I would avoid them at all costs.
 
Thanks for the info Bondo,
I have personally been quizzed about C-clips with my old mustang. I guess they had a reputation for the broken axle problem. And my local track in Colorado seems to be pretty strict on the rules. There isn't any reason not to comply considering the work I'll be doing to the axle anyway.

The 9" bearing retainers are fine for road racing right?
 
It must be friday and everyone is coasting into the weekend. Everyone's IQ seems to be at least 30 points lower than usual. Please tell me you don't actually need me to explain what's better about thicker tubes...
The jury is out on if NHRA will consider discs "a satisfactory means of axle retention". I've never heard of a tech guy ever even asking about c-clips though personally...

Ken,
The is a metal tag on the rear ends attached to the diff cover, there is a number that gives the ratio with a letter in the middle, like a 3.73 is a 3x73 If there is and "L" ther is is a limited slip. Like an 3L73 is a 3.73 with a posi. SOmehting like that. Look for an "L" anyways.

Kepe in mind most c-clip eliminator kits are OUTLAWED for roadracing- they don't like side loads and tend to want to leka diff oil onto your brakes., I would avoid them at all costs.

I'm a believer that over-kill is over-kill, why not use 4"x .375" wall tubing by your thinking??

axle tube diameter is based on overall vehicle weight and capacity, I'd almost be willing to be that the tubes are smaller or thinner for the Mustang applications....

I'm all for having strong parts, and for the OP, he might be pushing the limits, we all know the weak link to the factory 1031s or whatever are the center diff and axles, if we replace the center diff with an alloy steel spool and replace the axles with new alloy axles, then possibly the next weak link "might" be the housing..then again, it might not for most all applications
 
It must be friday and everyone is coasting into the weekend. Everyone's IQ seems to be at least 30 points lower than usual. Please tell me you don't actually need me to explain what's better about thicker tubes...

The jury is out on if NHRA will consider discs "a satisfactory means of axle retention". I've never heard of a tech guy ever even asking about c-clips though personally...

Ken,
The is a metal tag on the rear ends attached to the diff cover, there is a number that gives the ratio with a letter in the middle, like a 3.73 is a 3x73 If there is and "L" there is is a limited slip. Like an 3L73 is a 3.73 with a posi. Something like that. Look for an "L" anyways.

Keep in mind most c-clip eliminator kits are OUTLAWED for roadracing- they don't like side loads and tend to want to leka diff oil onto your brakes., I would avoid them at all costs.

Tag image for you. See where it says 3L73? that'll be a 3.73 diff ratio with an LSD. Just to clarify for the hard of understanding, the important part is the "L"

DSCF0002.jpg


Keep in mind most c-clip eliminator kits are OUTLAWED for roadracing- they don't like side loads and tend to want to leka diff oil onto your brakes., I would avoid them at all costs.

Thanks- I didn't know that.
 
Care to share what calculations you used to determine that the material cross section in question is overkill? Or are you saying it is overkill arbitrarily?

Axle tubes for "real" axles come in 2 sizes- 3" and 3.25". This is a very standard tube size - and not typically called "overkill" by anyone. 3.25" is the "9 inch style" axle tube and most everything else built to hold power is 3".

The more desireable GM housings have axle tubes this size as well.

So we have a whole raft of proven, solid axle configurations that use 3" or 3.25" axle tubes. And a dana 30 that is just a carry over of the dana 27 as used in 80hp, 2300lb PV544's. And you're saying the Dana is the "right" size and all of the proven durable axles are overkill? Good luck with that.

The axle tubes "see" all of the engine torque as transmitted via the suspension links.
One of the weak links of the 8.8 is actually that the axle tubes are held in the housing via welded plugs and the tubes actually turn inside the diff (easily fixed by welding the tubes to the housing).

Part of what is hard on axle splines is that when you torque on the pinion the whole housing and axle tube assembly tends to flex and misalign the axles relative to the carrier.

Increasing diameter improves torsional stength exponentially.

Ken, Don't know much about the 9" bearing retainers, but I like your reasoning in modifying the length and then welding on whatever bearing housings are appropriate- I am guessing what you're talking about is more like converting to a semi floater with a tapered roller bearing as opposed to just a press-on ballbearing with a seal in the housing. That would be the best way to go.
 
I would go with a 9" Ford. It would probably cost less than a 8.8", but if you can get a good deal on a 8.8", go for it. These are both very easy to work on and set up correctly. So get the rear axle and customize it for your needs, limited slip or locker, stronger axle if you are going to be using big slicks, ring and pinion ratio. One thing nice about the Ford axle is that you can take several pumkins already setup with different ratios. A change takes about 15 minutes.

If you are shopping the junkyards, look at the axles in station wagons and pickups and find a pumkin with a "N" cast on it. The N stands for nodular and is a stronger housing.
 
The one thing that gets me, with all this talk of 8.8" and 9", is the target 1/4 mile time of sub 11 seconds.
That's quite a lot of torque to be pushing through a diff, considering the car's going to be 1300kg+ ... I just have a suspicion that the 9" from the get-go would save on wasting an 8.8" first.
And as far as the weight difference; if we're talking about the sort of power that pushes a 1300kg+ car to a sub-11s quarter, I don't think it's all that relevant.
 
Care to share what calculations you used to determine that the material cross section in question is overkill? Or are you saying it is overkill arbitrarily?


I guess I was looking at this from my 242's needs as well as those that don't plan on putting down 400hp to the rear wheels with slicks :)

I'm all for having parts that won't break and I've had my fair share of Ford 9" rear ends on my Mach I's in the past (i've also had the "pleasure" of having a few drum braked axles decide to part ways with the rear end assembly, luckly I was able to jack the car up, kick the axle back in and make it home to repair with a new bearing :) )
 
The one thing that gets me, with all this talk of 8.8" and 9", is the target 1/4 mile time of sub 11 seconds.
That's quite a lot of torque to be pushing through a diff, considering the car's going to be 1300kg+ ... I just have a suspicion that the 9" from the get-go would save on wasting an 8.8" first.
And as far as the weight difference; if we're talking about the sort of power that pushes a 1300kg+ car to a sub-11s quarter, I don't think it's all that relevant.


There's plenty of nine second cars on 8.8" rears. There's none of us here that'll break one. I think you'll see the 8.8" becoming more popular over the years as the 9" is getting older and rarer (unless you have the funds to buy a brand new axle, of course) in the junkyards.
 
Forg, What are you referencing that suggests a 31 spline 8.8 is no good for 11's in a 3200lb car? You think he will "waste" and 8.8? How come?

Go to a mustang forum and tell them you plan on upgrading your 8.8" to a 9".

They will tell you to convert to 31 spline and leave it unless you plan to exceed 600hp.

600hp in a 3200lb car should be good for high 9's.

edit: BBQ beat me...
 
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