I'm having some work done on my car at the moment. I'm switching my original 67' mustang coupe's rear end. It's being converted to posi- and I'm throwing a 3.89 gear in there. I thought it was a 9" rear end but it turns out it's an 8.8". My mechanic tells me these parts are rarer and its going to cost almost double the amount that it would with a 9". He also told me convertting to 9" is going to be just as expensive because of the driveshaft u-joint etc.

So I told him to go ahead and order the parts for an 8.8" rear end posi. Will it still have decent strength as compared to a 9"? I'm planning on swapping motors next year to a 350-400 hp engine. 8.8's can handle that? Did I make the right move sticking with an 8.8" posi as apposed to converting to 9"?

 

You don't have an 8.8" rear unless someone put it in there. You probably have an 8 inch, which really is enough for you plans. The parts are available, and priced close to the 9" anyway.


Get a new mechanic.

 

I hope it is an 8.8 because if it is not and he puts those parts in that rearend it could end up a mess and about triple the cost. Get a second opinion...

 

Yea I have an 8.8 in my car.....its a 65 with about 330-360 HP....so it can def handle it.....I beat on mine all the time

 

its easy to tell the differance

8.8 has a diff cover on the back, 8" & 9" do not
8", 9" have drop out 3rd members, 8.8 dont

install $ is probably higher on an 8.8 (going rate here is 250-300)

posi about the same for all 3 @ 400-500
gears 150-210
install, bearings, etc, 100

sounds like you need a new mechanic

 

what do you mean by drop out 3rd memeber?

 

You don't have an 8.8 you have an 8" or otherwise know as an 8 3/4".
8.8 are whats fitted to current mustangs, and noobs often mix them up.
The parts are getting a little harder to find for the 8 3/4", however there are still plently of aftermarket gears available.
An 8 3/4" will handle up to about 400 hp pretty well, but their limited slip system is garbage. for the money you would be much better off going for the detroit truetrac centre. These are available from summit for about $400. and will give you better results.

 

Ford 8" and 9" have a "third member" it unbolts from the front side of the housing, and the gears, carrier come out from the front.

Dana, and 8.8"s(and others) have a "diff cover" on the back side of the axle housing... when you remove it you can see the carrier, gears.... to remove the carrier and gears you must also pull the bearing caps....

the ford 8" and 9" is easier because when you pull the third member you can set up the gears on a bench, not working under the car..... this is one reason the Ford 9" has so many aftermarket parts available to dragracers... easy swaps (if you have a spare you can change it trackside) (dont try this with a Dana or an 8.8")

 

I have an 8.8 (out of a ford explorer) w/disc brakes, LS, 3.73's the width is 59 3/4" (1/2" wider than the 8" i removed)

is the 8 3/4 a newer mustang rear axle ?

 

oook then, I have an 8" not an 8.8". My mechanic described it as 8 3/4 rear end. He said the price of converting 8" to posi with a new gear ratio will be double the cost of the 9". Sounds like I'm getting ripped off here.