8.8 rear in a 70

[hughnews1]

+2 on Exp 1995 $100 and use the alum driveshaft from the exp pay $20 at JY LOL my welder change the spring area . ready to install ooops now to S.b the coupe

[j persons]

One thing that hasn't been mentioned, the 8.8 consumes less HP than a 9". So theoretically, you will be faster in a quarter mile using the 8.8 assuming everything else is equal, gears, brake drag, etc.

[Maxum96]

Originally Posted by j persons

One thing that hasn't been mentioned, the 8.8 consumes less HP than a 9". So theoretically, you will be faster in a quarter mile using the 8.8 assuming everything else is equal, gears, brake drag, etc.

How do you figure it uses less HP? The ring gear is only .2" smaller. If there is any less parasitic HP loss, it's very minimal. And unless you doing serious drag racing, who cares if there is minimal HP loss?

If you can't find a 9" out of a Mustang, it's not hard or expensive to modify a 9" out of a full size ford car or truck to work in a Mustang. I took a 9" out of a junkyard F150 and narrowed it to fit in my car. By reusing the axles and center section out of my old rearend, it cost me only about $250 (including cost of buying the pickup 9") to build a heavy duty 9".


Stock housing on left, truck housing with back brace on right

[j persons]

The 8' and 9" rear ends use a deep hypoid gear angle, where as the 8.8 doesn't. The deep hypoid angle is about 10% less efficient, depending on the gear ratio, than a non hypoid gear, and that directly translates in to increased performance and fuel millage. You can see this your self by turning the pinion flange on a 8.8 by hand then try the same thing with a 9". The 9" will be harder to turn than the 8.8

The deep hypoid angle axle was introduced to offer a flatter floor and less of a drive line hump in passenger cars.

[Maxum96]

You're right about the hypoid gear angle (where the pinion gear sits in relation to the ring gear). I forgot about that. I was only thinking about parasitic drag. But even then it's not that great. Saying that you can feel the difference by turning the pinion flange is not a good indicator. You can have two identical rearends and one can easier to turn than the other. Newer bearings, different gear ratios, etc can all effect how easy it to turn a pinion by hand. The numbers i've seen is that the 9" rear uses 3%-5% more power to turn than a 8.8" rearend and then that's at higher driveshaft speeds. But the 9" is stronger and less likely to break than the 8.8 rearend.

If power loss was so great with a 9", why do all the professional racers (Pro Stock drag racers, NASCAR racers. etc) use 9" rearends instead of GM 12 bolt or 8.8 rearends? They're always trying to squeeze out ever bit of power out of their cars.

[stangg]

Originally Posted by higher power racing

64-70 Mustang

This is the kit I'm using I havent installed it yet but it uses a mustang 8.8

That AJE kit looks pretty damn nice... especially for the money. Found this old thread on VMF when googling for more info on it.
AJE Rear Subrame Kit and other rear suspension parts

[brianj5600]

The reason PS and NASCAR use 9" rear ends has little to do with my car. That is why I chose an 8.8. NASCAR likes the near unlimited ratios and quickess that they can be changed if you have several chunks ready to go. The PS guys need the strength and have no parts that interchange with a stock unit.

The weakness with the 8.8 is the fact that there are not any pro gears made for an 8.8. Pro gears are made of a different alloy that will stand up to higher shock loads, but wear quickly on the street. There are guys on small tires putting over 2000 hp to 8.8s and gears are a maintenance item changed on a regular basis before they fail.

I have about $1100 in my 8.8 and don't think I could build a 9" to take the same power for the same money. It is an f-150 housing with 9" ends, 35 spline axles, spool and girdle. I am thinking it is not breaking a sweat under 1000hp. I plan on testing it to about 900.

[Maxum96]

Originally Posted by brianj5600

I have about $1100 in my 8.8 and don't think I could build a 9" to take the same power for the same money. It is an f-150 housing with 9" ends, 35 spline axles, spool and girdle. I am thinking it is not breaking a sweat under 1000hp. I plan on testing it to about 900.

If that was the case, then why aren't all the serious racers using 8.8 rearends? It's not because of a lack of selection of gear ratios. If racers started using 8.8 rears, every gear maker in the world would make tons of different ratios just like the 9". And they'd make them out of the softer higher nickel content steel race gears are made of. But because not as many people run 8.8 rears as 9" rears, there's not as much money to be made.

[brianj5600]

There are a lot of people that wonder why there are no pro gears. No body will know the weak link of the 8.8 until pro gears are readily available. It will likely be the 35 spline axles. The carrier bore being the limitation. If you venture over to yellow bullet you will see sub 5 second 1/8 mile and some low 7 second or even high 6 second 1/4 mile cars running 8.8s. Several threads in drivetrain tech. The generally accepted rule is stock gears are good to about 1.20 60' times at 3000 pounds. I still say an 8.8 will out live a stock case 9 inch.

[OCHOHILL]

Originally Posted by MustangChuck

The SN95 rear is about 1.5" wider (hub to hub) than a 70 rear. If you are planning to use aftermarket or late model rims, this shouldn't be a problem. I am planning to use the rear from my 94 GT donor. I am running 97 GT rims and with the old rear end, needed 1" spacers. With the new rear, I should only need 1/4" spacers.

Chuck

Are you sure about that?

Factory Axle Widths

I am asking because I bought a fox rear axle I am converting to sn95 for a 67. I thought the were the same width exactly.

[brianj5600]

the housings are the same length and interchange. Each axle is 3 quarters of an inch longer for 1994 to 1998 axles. I believe they call that brake stick out. At least strange engineering does if I remember correctly.

[GypsyR]

Funny to be discussing the whys of nine inch rears when it was figured out like 30 years ago. A Nine is TOUGH. And relatively easy to change gear ratios in the pits. A GM 10 bolt rear and an 8.8 share a bunch of design similarities. So a 10 bolt is also more efficient than a nine. But the GM guys for years have been swapping their 10 bolts (and 12 bolts) out for Ford nines. The Dodge guys tend to have pretty good luck with their Dana rears in the durability department but you will still see nines under Dodges where they need to change ratios from time to time.
For many years nines have been the go-to rear to handle power and for quick ratio changes on a reasonable budget. A nine inch rear may be one of the best all-around pieces Ford ever designed. It doesn't hurt that there is a ton of aftermarket support for them either.
And they don't need "c-clip eliminator" jury-rigs either when you have a car faster than 10 seconds in the 1/4.
You figure it out pretty quick drag racing. If you've been regularly running a 10 bolt or 8.8 against Joe Bob with a nine it doesn't take too long to notice that Joe Bob has been running the same nine all season where you've just blown up your third (expensive) rear end. And that's about all it boils down to. At certain power levels a nine inch rear is money well spent. Drag racing is an expensive hobby.

[brianj5600]

Originally Posted by OCHOHILL

Are you sure about that?

Factory Axle Widths

I am asking because I bought a fox rear axle I am converting to sn95 for a 67. I thought the were the same width exactly.

Reread the link. The second post clarifies it.

[brianj5600]

Originally Posted by GypsyR

Funny to be discussing the whys of nine inch rears when it was figured out like 30 years ago. A Nine is TOUGH. And relatively easy to change gear ratios in the pits. A GM 10 bolt rear and an 8.8 share a bunch of design similarities. So a 10 bolt is also more efficient than a nine. But the GM guys for years have been swapping their 10 bolts (and 12 bolts) out for Ford nines. The Dodge guys tend to have pretty good luck with their Dana rears in the durability department but you will still see nines under Dodges where they need to change ratios from time to time.
For many years nines have been the go-to rear to handle power and for quick ratio changes on a reasonable budget. A nine inch rear may be one of the best all-around pieces Ford ever designed. It doesn't hurt that there is a ton of aftermarket support for them either.
And they don't need "c-clip eliminator" jury-rigs either when you have a car faster than 10 seconds in the 1/4.
You figure it out pretty quick drag racing. If you've been regularly running a 10 bolt or 8.8 against Joe Bob with a nine it doesn't take too long to notice that Joe Bob has been running the same nine all season where you've just blown up your third (expensive) rear end. And that's about all it boils down to. At certain power levels a nine inch rear is money well spent. Drag racing is an expensive hobby.

I am guessing you don't get to the drag strip very often.

[GypsyR]

Ok.sure.