Thread: 7.5" Ford rear

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Been beating on this 82 Mustang to race and now I'm at the rear end. The 7.5 has a cracked bearing cap and the ring & pinion are mush. I need to go with 4.56 gears if calcs. are correct, but am wondering if I should loot an 8 or 8.8 rear from the local yard instead of spending time and money on this rear end. Am hoping on 500 to 550 horses to hammer it with and don't know if this little guy can take the stress-girdle or not. Any ideas???

Originally posted by stangwrecker
Been beating on this 82 Mustang to race and now I'm at the rear end. The 7.5 has a cracked bearing cap and the ring & pinion are mush. I need to go with 4.56 gears if calcs. are correct, but am wondering if I should loot an 8 or 8.8 rear from the local yard instead of spending time and money on this rear end. Am hoping on 500 to 550 horses to hammer it with and don't know if this little guy can take the stress-girdle or not. Any ideas???

why not go ahead and put the 9" in there and forget about it. thats the only way to go.

you should also consider stiffining the unibody because 500 horses to that mustang, let the hammer down 1ce and the car could twist like a paper clip. 9" sounds best for your application.

My vote would have to be the same as Bill, Matt, and lt!, no way the 7.5 would live. Maybe you could get lucky and find one of the 8.8" with the factory disc brakes?? A 9" would be the best set-up.

Thanks for the input- I should have told you that I am on a fairly tight budget and have never dealt with a rear end this in depth before. I would have to back half the car and set up for ladder bars or four link if I went with the 9 inch wouldn't I? Or is there a more direct route to this than that ?

I don't belive it's that big of a deal. as Dave said, you could get lucky and find a ford explorer with an 8.8" and that would take it but your 7.5 I dout has a chance at surviving 500+ HP. The 9" will cost less in the long run.

Originally posted by stangwrecker
Thanks for the input- I should have told you that I am on a fairly tight budget and have never dealt with a rear end this in depth before. I would have to back half the car and set up for ladder bars or four link if I went with the 9 inch wouldn't I? Or is there a more direct route to this than that ?

500 hp is a lot of hp for the st. but if youve got it you should use it, and the only way you can do that it you have to have something that will stay togother and hook up when you wont it to. you could put the 500 hp motor and 7.5 dif. with 4.56 gear in it and ride around and porfile all you wont, but if youer (going to hammer it) as you say then you need the 9" dif. with at least frame ties installed. the ladder bars or 4 link would be for handling not strength. leaf springs should be strong enough but you cant do much with them far as handling goes. put your 500 hp motor in and the 9" dif. use your leaf springs and install some frame connectors youll need to look at the shocks. thats my story and im sticking to it.

If you are setting your mustang up for racing then and don't know much on chassis and rear ends at all or not much then I recommend a couple books that I just got the other day that help a lot. One of them is "Hot Rodders Bible" the other is "So Cal Speed Shops, How to Build a Hot Rod Chassis", those are very helpful and will teach you all about the ladder bars or 4 link or whatever you wan't to do. Well worth the 15 bucks on each book I think. Now I am with everyone, I have done some research on rear ends and a 9 inch sounds good. If you will have about 500 HP then you will need to strengthen up the chassis a bit so it doesn't do what Matt there said....

Thanks for the advice. I have a 9 inch sitting and to be honest-I was hoping what was in the car would work. Guess I better get started on tearing the 7.5 out. I'm sort of getting impatient as I have had my engine setting on the stand for a couple of months and want to get it in and going soon!

Originally posted by stangwrecker
Thanks for the advice. I have a 9 inch sitting and to be honest-I was hoping what was in the car would work. Guess I better get started on tearing the 7.5 out. I'm sort of getting impatient as I have had my engine setting on the stand for a couple of months and want to get it in and going soon!

if youer just going to ride go with the 7.5. i try to do as much to the the car as i can before i start the motor because once i start it up and ride, then its hard to go back to work on it.

The car won't see the street again-too radical and already stripped of its fat.Caged, subframe connectors and all. Guess I'm trying to weenie out of the nine inch just from engineering standpoint!