How much hp can the ford 7.5 handle?


Tokar347

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I'm buying a new v8 from blueprint to replace my current worn out v8 (no I'm not going to build the current engine because it's much simpler and less confusing than building an engine with unknown specs) 84 ranger and it makes about 390hp. I plan on pairing it up to my current c4 auto and running my ford 7.5 for the rear diff with 3.73 gear ratio and the Yukon posi in it. Anyone able to get me some numbers on how much hp it can handle? I also have a shortened ford 9" for it that I want to convert to disc brakes and possibly use that instead as a backup but I have to fabricate mounts for the leaf springs and struts that I kind of don't want to do. Any insight will help
 


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I don't know. Everything I've read says they are a pretty tough rear end. Run it til it breaks then upgrade it.....
 

Tokar347

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I don't know. Everything I've read says they are a pretty tough rear end. Run it til it breaks then upgrade it.....
From what I've seen around, even if the 7.5 is rated for a lower hp than the 390 I'm going for, using an auto trans helps soften the shock or stress on the diff as opposed to the manual transmission or something along those lines. Have any knowledge on that?
 

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The mustang guys put a lot of power to them, I'm with the above, run it till it brakes then put in a 31 spline 8.8" in there... 3.73 limited slip axles are the easiest to find in the junkyard and all you should have to do is weld on spring perches and shock mounts, maybe the flange on the rear drive shaft at most or possibly shorten it it an inch depending on a lot of things...
 

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Mustang GT's stopped using 7.5's in 1985 when they produced 225hp, that's apparently Ford's opinion of their durability because Ford wouldn't have spent the money to install 8.8's if it wasn't needed. Or you could run skinny tires that would spin and not stress the rear end.
 

rusty ol ranger

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You wont break it unless it hooks hard.

HP dont break stuff anyways, torque does. At 390hp your pry....450 or so on torque? That is asking quite a bit.

Like stated above the auto trans wont put the shock load on shit like a manual will, but the 7.5s longevity will depend on your stall speed, tire grip/size and your right foot.

If that C4 is stock dont expect it to live long either.

The mustang ran a 28 spline 8.8 IIRC, theres not a huge strength difference between that and a 7.5.

Your 9 inch should fare well though.
 

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When considering the question above, all I can think of is this...

tumblr_mx9dh3nWWk1t55xupo1_400.gif
 

rusty ol ranger

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I think itll be ok for a bit. Tires will play the biggest role. Espicially with a light ass ranger rear end.
 

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Mustang GT's stopped using 7.5's in 1985 when they produced 225hp, that's apparently Ford's opinion of their durability because Ford wouldn't have spent the money to install 8.8's if it wasn't needed. Or you could run skinny tires that would spin and not stress the rear end.
Only difference in strength between a 7.5 and 28 spline 8.8 is the diff.

The spiders on the 7.5 is the weak link.
 

rusty ol ranger

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Only difference in strength between a 7.5 and 28 spline 8.8 is the diff.

The spiders on the 7.5 is the weak link.
Yes but how often does a 7.5 grenade?
 

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My buddy grenaded the 8.8 in his mustang.

it was only making 900 hp...
 

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I've owned 4 different 7.5s and they are all still in working order. Never been rebuilt or needed to be taken apart. I know its nice to have the bigger breaks on the 8.8 though I'm sure you could put em on a 7.5 as well. The main reason To switch is if you are running 35" tires. The bigger ring gear is stronger then the 7.5. Relatively speaking. And I think the hp rating isnt as relavent as the GVWR. Which is the one of only reason the explorers run 31 spline 8.8.
 


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