7.5 28-spline locker reliability opinions wanted

[Just_Randy]

Your "grandma" is not very average if she drives like any of those examples...

No, my granny isn't very average. Her foot is heavier than most. But this guy lives across the street and everytime I see him drive by, he shifts at 2500 rpm. Some people have a knack for breaking stuff... and he got a double dose of it.

But yeah, the 28 spline Ford stuff is fairly decent.
Ford shafts have a different spline pressure angle that isn't cut as deeply into the shaft as on Dana shafts. This makes the 28 spline Ford shaft about on par with a 30-spline Dana shaft.

I was thinking there HAD to be something different other than the .04" diameter difference. I just don't read much about broken 7.5 axles.

welded in a light linked car a 7.5 can get lucky, long time. i too have seen it in light fox cars.



i hate the 7.5. in a leaf spring application and my chassis with a load, i can bust a 7.5 in front of you right directly after i bolt it in my truck with a mere 260 rwhp. i have not lost that bet yet.

What breaks in them?

arb.....in a 31 spline 8.8......hate that fawker too. but i way overloaded that past intentions as well.

i cant believe how long some shafts last over others when spooled on the street. the 28 splines usually pencil/fail in short order if run with stout springs or traction bars if there is a load on them.

By load do you mean cargo? Or HP?

 

[bobbywalter]

cargo and hp.


case deflection is what breaks them. i had some top people work on that with me.

 

[Just_Randy]

The cases break in them?

I'm not running a lot of HP. I think its 150 max at 5000 rpm or something.

With an open diff, both axle shafts are pushing the truck. With a locker, the slowest wheel gets all the power. So if I'm pinned in some big rocks and one wheel is off the ground, the wheel tounching the ground is going to be the only thing pushing the entire weight of the truck over the rocks. Can the axle shaft handle that kind of torque? And if it can do it once, how many times can it do it before it fatigues and breaks?

 

[hdmm]

The cases break in them?

I'm not running a lot of HP. I think its 150 max at 5000 rpm or something.

With an open diff, both axle shafts are pushing the truck. With a locker, the slowest wheel gets all the power. So if I'm pinned in some big rocks and one wheel is off the ground, the wheel tounching the ground is going to be the only thing pushing the entire weight of the truck over the rocks. Can the axle shaft handle that kind of torque? And if it can do it once, how many times can it do it before it fatigues and breaks?

Throw a Lock-Right in there and call it a day. The axle shaft will be fine as long as your foot isn't made of lead. The Lock-Right will "unlock" on the street on corners so it is streetable and you won't break stuff. You could also upgrade the axles later on if you wanted, Moser makes a set of nice axles for the 28 spline 7.5 and 8.8 Ranger axle, they are pretty resonably priced and increase the axle strength by like 35% according to Moser. You can even go one step further and add a Moser C-Clip eliminator kit too for added security.

I ran a stock 7.5 in a Mustang that I swapped from v6 auto to 5.0 stick and it never broke.

 

[Just_Randy]

So, you would go this route instead of finding an 8.8 with 31 splines?

 

[bigmark303]

I have a 7.5 28 spline with a detroit locker in it. Its been just as reliable as my 8.8 28 splines.

I had it under a 2.3L 2wd truck 3.73 gears and 34x10.50 tires. I used to haul 2,000lb loads of wood down skidder trails for about half a year. Since then it has been sitting under my 4.0L 4x4. I swapped the gears from 3.73 to 4.56. Its been still nothing but reliable and I run 33x10.50 tires and off road 8-12 solid hours a week and the rest of the week im crawling down the skidder trails to collect wood.

If you dont have propper gears and constantly have to stomp on it vs just crawl you are always gong to break stuff.

 

[bobbywalter]

The cases break in them?

I'm not running a lot of HP. I think its 150 max at 5000 rpm or something.

With an open diff, both axle shafts are pushing the truck. With a locker, the slowest wheel gets all the power. So if I'm pinned in some big rocks and one wheel is off the ground, the wheel tounching the ground is going to be the only thing pushing the entire weight of the truck over the rocks. Can the axle shaft handle that kind of torque? And if it can do it once, how many times can it do it before it fatigues and breaks?

when i say case deflection, i mean the actual housing is flexing causing inner deflection as well.

 

[Just_Randy]

Easy enough to remedy that with some steel and a welder.

 

[bobbywalter]

Easy enough to remedy that with some steel and a welder.

or a real axle for a 150 bux.


then again i was killing 31 spline arb 8.8's as well.


if your staying stock with tire and powertrain...7.5 is fine.

7.5 with locker is better.

 

[Captain Ledd]

Pretty sure the Ford axles run a little better material as well than a lot of the Dana axles do, from the factory.