7.5 rear from 4cyl
- Thread starter softballnrd27
- Start date
Sure, no sweat....provided you stick to your word of "easy driving". Start spinning the wheels and hard shifting the car and you'll end up on the back of a tow truck though.
rd
Founding Member
My 82 has been high 12's with it's 302/C4 combo on a 79 7.5 in axle with 4.10 gears and drag radials.
Not recommended, but it's worked for 10 years. Car is light, only runs 1.90 sixty foots.... I have several 8.8's in the garage if it quits.
Probably fail quickly with a stick shift and abuse.
Not recommended, but it's worked for 10 years. Car is light, only runs 1.90 sixty foots.... I have several 8.8's in the garage if it quits.
Probably fail quickly with a stick shift and abuse.
capri debris
Member
A 7.5 will only fail if you get good traction. On the street without drag radials, you'll be fine because the tires will spin before the 7.5 will break.... however, if you take it to the track with some slicks or power shift like mentioned above, you're going to be picking up pieces.
When I was a teenager, my old '85 Ford ranger went about 12km with nothing more than a stock 302 under the hood with an AOD backing it.
It's never a question of "if" it's going to go with those old 7.5" ers...but when.
He'll be FINE as long as the tires spin!?! Dude, don't tell him that unless you're willing to foot the tow bill. The old 7.5" rear end was practically made of glass. It won't take much traction for him to compromise it. Certainly much less than a set of drag radials at a race track would provide.
capri debris
Member
Back in '84, I bought a stock 5.0 5 spd Capri with 170 hp. It could spin the tires easily and I pounded the guts out of it and power shifted often and never broke the 7.5 it came with.
The physics behind my statement is if only 170 stock hp is enough to spin the tires, you could put 1000 hp in front of a 7.5 and not break it as long as you don't do anything to get more traction. Once the tires loose traction, it doesn't matter how much hp you have, the pressure is relieved from the rear. Big hp is only uselfull if you can get it to the ground and once you cross the threshold of traction, you are no longer putting stress on the drivetrain.
As long as he is traction limited, he won't break the 7.5 with 300+ hp because all the extra hp over what it takes to break the tires loose is not going to be stressing the drivetrain any more than the 170 hp my '84 came with from the factory.
Now take a car with a 7.5 and 300+ hp to the track with some slicks and turn all of that hp into useful hp by sending it all through the drivetrain with tires that stick... and something is gonna give.
On the street with normal traction street tires, he will never come close to breaking the 7.5 before the tires go up in smoke. And no, the 7.5 is NOT made of glass... there are many on here and other boards who will tell you they are running a 7.5 with big hp and it's still holding up. Yes, an 8.8 is good insurance, but the 7.5 isn't as weak as some may think.
I don't recommend that the OP goes beating on the 7.5 to find out if I'm right, but rather he asked if he could get by with it until he has the cash to upgrade... and my answer to him is yes, it will definitely hold up.
Agreed, for what you'd sink onto a 9" to get it bolted into and working with your Fox body, you could build an 8.8" to take twice that power.
darthcual
Member
True that 9 is over kill but he maybe planning for the future. Any way, I rode drag radials on 285 hp and over 300 ft lbs of torque with full drag suspension on a 7.5. Not optimal, but it never broke at the strip. Ran 12.9XXX's with a low sixty foot (dont remember the exact numbers)
