I have a big offroading truck that I am rebuilding the for 9" rearend in. What I am looking for are suggestions as to whether I should get a locker or put in a spool, and why you would do that. I appreciate it.

 

I don't think a spool is the way to go, but then again, I'm not in off roading much, just seems like it's a drag race thing. I have heard of doing a locker way more often. Spools turn both wheels the same speed all the time, hence good for going in a straight line at the drag strip.

 

A spool is a fulltime locker, and if it isn't driven on the street much and manueverablity isn't a issue than there is nothing wrong with a spool. Personally I would rather have one I could turn off and on though.

 

The 9" isn't strong enough for a "big offroad truck". It's not even as strong as the 8.8".

If you need strength, use a 9.75" or even a 10.25".

The type of diff you need depends ENTIRELY on what you plan to do with the truck. Specifically. Sand? Rocks? Forest? Mud? Snow/Ice? Some combination? Will it be street-legal &/or a daily driver? What kind of tires, and will you have a street set & an off-road set? Read this.

 

The 9" rear end is 3 times as strong as the 8.8. Every nascar car runs a version of one last time I checked, even the Chevys. 9" are alot easier to work on. When I ran my 69 F150 we would put the 4:56 gears in at the drag strip, run the quarter, then put the 3:25s in for the trip home. The axles are held in by four bolts at the end of the axle tube. Loosen them, pull the axles, drop the driveline, pull the pumpkin, put the new pumpkin in, push in axles, fill it full of fluid, reinstall the driveline and youre off. Just makesure you get a 9" and not an 8". If you can get a socket on the bottom pumpkin bolts, its an 8". 8" limited slip diffs arent very tuff. Very rarely did they come with good gears. I had a 65 Mercury Caliente that had a 289 and 3:70 limited slip 8". But thats the only set Ive ever seen personally. By the way all MustangII's with a V8 had a limited slip 8" but it is very weak.

 

Even recognizing it as an exaggeration, that's ridiculous. The 9" isn't popular because of strength - it's popular because it's cheap, common, & easy to swap out the weak 3rd member when it breaks or wears out.

It's like saying AA batteries are stronger than Ds, and that's why so many cameras & remotes use them. Popularity has NOTHING to do with strength or any other desirable quality, and often doesn't make sense at all - just look at Domino's greased cardboard, or any recent pop band.

 

Well, I plan on doing allot of on-roading, along with the occasional "thats a nice mudhole" driving. I am going with the 9" due to its ease of use as well. I have 44" tires on the truck. So, I gues I should go with a truetrac or something along those lines.

 

44s are WAAAAAAY too big for that axle; even with the light use you describe. 35s are the recommended max, if you're careful. But you can find a LOT more info about this & plenty of people who will tell you the 9" is the way to go (& how to do the swap) on FSB. Just do a few searches before you post a new question because it's a popular topic, and there's already a lot of info up there.

 

My initial question was not covered a whole lot, that would be the reason for the post. As a matter of fact, I was not asking if the 9" would hold up, becuase it will. I was mearly trying to get opinions of people who have run a spool and a locker and wanted their input. Sorry if the question put anyone out.

 

In that case:
I'd recommend an open diff because anything else will make the axle even MORE likely to grenade.

 

The 9" is popular because of it's housing, ring gear, and axle shaft strength, on and off-road and because of it's light weight. The ring gear is huge, .2" bigger than the 8.8. Thicker ring diameter also, including an extra support shaft on the pinion gear. Plus, if you are really worried about the "weak" non-nodular 3rd member, buy a nodular 3rd member off of ebay, set it up with a 35 spline detroit, and have fun.
Go to this website, and click on the link labeled,
"Why a Nine?"
http://www.sunrayengineering.com/

 

Are you nuts? A good friend of mine ran 44's on his F-150 for seven years without breaking ANYTHING, AND he used to run the thing in bog competitions (Full throttle throught 150 feet of 1-4 foot deep mud) as well as use it as his DD.
As far as the 8.8 being stronger than the 9 , where in the world did you hear that?? Have you ever heard of anyone swapping out a 9 inch for the "superior" 8.8? No. Because they aren't. Stronger than the Dana 20's, 35's and even the 44's, but the Ford 9 inch? That's the nuttiest thing I've heard yet. Thanks for the laugh!
Cheap? Common? Umm Steve? The 9 inch has been out of production since 1986. Don't look for your calculator, that's 20 years ago. Even custom 9 inch rear builders are having a hard time coming up with them. When they do find them, they aren't cheap.
Weak third member? Yea, that's why, when people want to upgrade their diff, including GM and Mopar guys, they choose: That's right!! The mighty 8.8!! It's better than that weak POS 9 inch! Buy one today! Heck, buy two! One for your neighbor, or a relative perhaps! Uhhuh.

 

If this vehicle is to be used on the street--AT ALL--do not use a spool. The tire contact patch from the big tires would stress everything for no reason. A Detroit Locker or other, would ratchet loose to allow for unloading of the torque bind while turning.
I have a 9" w/ a Detroit Locker that works fine on the street, and has for over 15 years. If I give it too much gas around a corner, it will lock back up and spin the inner tire like it's a spool, but that only happens once in a while.
BTW, don't pay any mind to what Steve83 says about either 8.8" OR 9"' rears. He clearly has been grossly misinformed on both.
If I saw an 8.8 on fire, I wouldn't cross the street to pee on it, but that's just my opinion.

 

Yes. Plenty of magazine articles written by people who wheel & build axles for a living have begun to acknowledge the 8.8's superiority over the 9. And 9 is by no stretch of the imagination "huge" - nor is 0.2" a big difference. Even if it WAS, an axle's strength is NOT based solely on ring gear size.

The 9" didn't become popular last year - it became popular 30 years ago, because it was cheap, light, & easy to find. But even today, it IS still in production. Ever hear of "Currie"? Do a few searches & I'm sure you'll run across it.
Yes, proven by the fact that it needs an extra bearing to hold the pinion gear in line.

You really seem to think that the ONLY reason anyone would choose or change an axle is strength - not so. There are MANY reasons & considerations, and strength is NO reason to choose the 9". It's a reason to choose the 9.75" or 10.25". Now, THAT's "strength".

 

Ok, based on that statement, why did you say the statement below?

Those axles just about have a bigger ring and pinion. What else is so great about them? Huge center sections? Expensive parts?

You might as well get a Corporate 14 bolt if you want to go big and beefy. Those things are way cheaper than a 9, and about twice as heavy