8.8" vs 9"

gzminiz · Sep 26, 2005

I spoke with a local guy this weekend and he was saying the 8.8 is lighter and provides the same durability that the 9" does. I was thinking about doing the mustang steve cobra brakes upfront and match them in the rear. The 8.8 would accomodate this a lot easier. What are the advantages/disadvantages of each? I here SN95 8.8 are exact width of a 67, True/False?

Edbert · Sep 26, 2005

Don't forget, the rear brakes on a Cobra are not the same as the front brakes of the same Cobra. Just pointing out that your attempt to "match" them will not mean they match

9" is a little stronger than an 8.8", the 9 is much easier to work on (removeable carrier no C-Clips), and the weight is about the same, the biggest advantage of the 8.8 is that it is more efficient (meaning more power to the wheels and possibly better mileage), and they can be found in boneyards under Explorers with LSD and rear disc brakes already on them.

rbohm · Sep 26, 2005

actually the 8.8 is quite a bit lighter than the 9" rear, but unless you use one from an explorer or ranger, you will have to remove the suspension brackets and weld on leaf spring mounts, unless you want to swap the fox body suspension over as well.

gzminiz · Sep 26, 2005

I understand the reear brakes don't look the same I guess better wording could be i want the whole set. The welding on leaf spring mounts is no big deal. The efficiency is interesting point for me though. I will have to take that into consideration. Any other opinions?

Thanks
GZ

302 coupe · Sep 26, 2005

whats the deal with the offset pinion on the 8.8? Is that an issue on some, but not others?

ForceFed70 · Sep 26, 2005

I'm curious as to why the 8.8 would be more efficient. They look to be the same mechanical style as the 9". I really can't see 1 being more efficient than another.

The 9" is stronger, but from what I understand the 8.8 is still good to over 300RWHP.

gzminiz · Sep 26, 2005

A local guy was under the impression that the 8.8 will hold up against 450rwhp no problem.

brianj5600 · Sep 26, 2005

Fox 8.8 is the same width as a '67. SN95 is about 2" longer give or take. The 8.8 has a higher pinion meaning less friction when the gears mesh. Most 9" rears in road racing use coolers due to heat caused by extra friction.

Edbert · Sep 26, 2005

gzminiz said:
A local guy was under the impression that the 8.8 will hold up against 450rwhp no problem.

Maybe he meant FWhp instead of RWhp?

With 450rwhp you're gonna want an aftermarket-beefed-up 9". 450 at the wheel s is close to 600 flywheel.

Also, torque is what breaks drivetrains not hp.

Regarding the widths, an SN95's 8.8 will fit under a 67-70 and allow the use of late-model rims without adapters.

65ShelbyClone · Sep 26, 2005

70_Nitrous_Eater said:
The 9" is stronger, but from what I understand the 8.8 is still good to over 300RWHP.

Thats is generaly true, but the c-clip type axles become the weak point when you throw alot of traction at them. If you break a c-clip axle, say bye-bye to your fenderwell. On the other hand, I know that 8.8s can be built to handle the power a high 7-second car puts out.

gzminiz · Sep 26, 2005

65ShelbyClone said:
Thats is generaly true, but the c-clip type axles become the weak point when you throw alot of traction at them. If you break a c-clip axle, say bye-bye to your fenderwell. On the other hand, I know that 8.8s can be built to handle the power a high 7-second car puts out.

So, what would be needed to make it handle a 7 second car? I assume some new axles but what else would need to be changed out.

66Runt · Sep 26, 2005

Read through some 5.0 Magazines and see the HP pumped through stock 8.8s

One other thing you need to watch for is that it takes a special kit to put Cobra brakes on the back of a Fox bodied 8.8. As it uses smaller end caps. They also used 4 lug axles.

I've got a '91 8.8 out of a GT just waiting on the 2-7/8" HD U bolts to get here so I can mount everything up and weld the spring perches in place. Then I'll build it and install it in my '66 with the Cobra rear brakes. Hopefully that will happen this week. It took a bit of work to figure the whole thing out, but it should be real nice!

Scott

SitDown · Sep 26, 2005

a stock 8.8 wont hold up long to slicks, ive even destoryed a carrier and axle on a 17" drag radial...but mildly upgraded, the 8.8 can be plenty strong...

A simple street strip setup of 31 spline axles (w/ or w/o c clip elims), decent carrier, and girlde will leave you confident that you'll drive home from the track after a day of 6k slick launches with your 4-500rw car.

getting a bit beefier, handling 1000rw isnt an issue...

rollin68 · Sep 26, 2005

Edbert said:
they can be found in boneyards under Explorers with LSD and rear disc brakes already on them.

Also 31 spline

Here is my take, I had an 8" so I knew I was going to need a whole new rear end. Found a guy with Ford's left over Explorer rears that we brand new. At the time I figured 31 spline, disc brakes, limited slip, 3.73 gears for 500-600 bux wasnt too bad and I would just figure out the offset dilema later. Well as time passed and my plans for the car got more agressive, it ended up going to Currie before it even got in the car, and they fixed the offset and added fordged axles, with 9" axle housings ends. So as I see it, if you dont mind hunitng for one, and welding on and off what needs to be done to it, and can deal with the offset or fix it, then go for it. People have done it with just welding on the spring purches, some get interefence. If yer gonna be pushing some serious power its not gonna be cheap anywaise, so you might as well get it done right, at least thats my take. Both 9" and 8.8" can be built to handle more power then most of us will ever have.

One side note, supposedly (and maybe some can confirm or deny this) the 8.8 is just like the Gm 12-bolt.

rbohm · Sep 27, 2005

as i recall the only part that does not interchange with the gm 12 bolt rear is the pinion seal, and perhaps the ring and pinion. everything else is the same as the gm 12 bolt.

Edbert · Sep 27, 2005

I know of a number of LS1 owners with serious power that are dumping their 12-bolts in favor of a FoMoCo 9". The ability of the 9 to stand up to serious power is the stuff of legend, every car on the Winston Cup has one, Pontiac/Buick/Chevy/Dodge.

(Yes I know it is no longer called the "Winston Cup", I also know Pontiac and Buick don't run the series anymore. But when they did they had a 9 under them.)

brianj5600 · Sep 27, 2005

The reason cup cars use a 9" is not because it is the best or the only one that will hold up. They use them because they can carry around pumpkins with different gears in them. If you don't plan on changing gears a couple of times a weekend, a 9" is a liability. Edbert, how much would it cost to duplicate your 9"?

Edbert · Sep 27, 2005

brianj5600 said:
Edbert, how much would it cost to duplicate your 9"?

Here's some details:
http://www.edbert.net/axle.htm

I got the 9 itself for only $100 (still have the center chunk and the 28s that came with it), new axles were a few hundred, the Wilwood discs were almost $600, I traded a 3.25 r&p for the 3.89, and the diff was another couple of hundred. I bartered some computer services for the r&p setup and the powder-coating. All in all the $1,350 is about right.

danny clemens · Sep 27, 2005

I know some die-hard Chevy guys that use the 9" Ford for drag racing. My brother-in-law being one of them. The 12 bolt kept breaking on him. He swapped it out for a 9" Ford and end of problems period.

68rustang · Sep 27, 2005

Fox 8.8 is the same width as a '67. SN95 is about 2" longer give or take...

The Fox and SN95 use the same rear axle housing. The extra 1.5" overall width of the SN95 rear comes from the disk brake/ABS axles.

Regarding the widths, an SN95's 8.8 will fit under a 67-70 and allow the use of late-model rims without adapters.

It's close, I do not know for sure if they will clear or not yet

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