I have a 91 F-150 two wheel drive pickup, my rear axle bearings are getting bad. After looking at the design like a Chevy I would like to install a older 9 inch rear end in my truck. I am hoping some of you guys may have either made this swap of looked into it. Can any one offer advice?

 

Yes: don't do it.

The 9" is a weaker axle than the 8.8", by design. It's popular because it's simple to modify & quick to repair when you tear it up, but the 8.8 doesn't tear up as often or as easily, so it doesn't need to be repaired as much. Also, it's prohibitively expensive (nigh-on impossible) to fit an ABS sensor to a 9". Furthermore: most 9" axles have a small stickout, which puts all the wheel load onto the lugs (lugcentric) rather than directly onto the rim (hubcentric).

8.8s are very common & inexpensive in junkyards, so do a little browsing. You'll be MUCH better-off.

 

Sorry Steve, but I dont agree, in my experance the 9inch is a far better axle assembly! What good is a axle being the inner race when the cagged rollers go bad as they seam to do so often! If I wanted a chevy axle I would have baught a chevy!

 

Oh sorry forgot, I could care less about the abs bs any how.

 

Isn't the VSS in the rear end? would that switch right over? I would seriously think\do a little more research about the 8.8 vs 9. Not saying you dont know what your talking about or anything, because I don't know your experience level and such. What I do know, is Steve 83 lives and breathes these trucks, he's the Chuck Norris of these things, For years now his advice has always made sense and more importantly been correct\concise\clear.

 

The 9" is not weaker than an 8.8 if you get a 31 spline unit. There are MANY version of the 9" and some are 28 spline though. As long as the vss isn't in the axle then ditch the sensor and all the abs junk. Even if the vss is in the housing you can still do it by relocating the tone ring (google brea auto electric). I've even seen people use an 8.8 tone ring in a 9" but it's a custom job. You might need to relocate the spring perches and build lower shock mounts. As far as drive shaft you may need a conversion joint as well. You can just measure everything out to determine what you need there. You can also swap disc's on pretty easy. I built my own conversion kit for less than 100 bucks. They're super simple, easy to work on, and uber upgradeable. They also aren't c-clip axles so if you break a shaft it stays in the housing haha.

I don't really have too many pics from when I put my 9" in my explorer. The entire rear axle swap was not difficult. I welded on new perches, made new lower shock mounts, and did my disc conversion.

 

Ford designed both of them, and Ford obviously thinks the 8.8" is far superior. They quit using the 9" in '86, and still use several variations of the 8.8" in cars, trucks, & suvs; front AND rear.OK, but that doesn't address the strength issue. You'll still be downgrading.Yes, even the 31sp 9" was always rated for less GAWR than any fullsize 8.8". And anything you can do to beef a 9 can be done to an 8.8 just as effectively, if not moreso.It is.If he was at the level to do that kind of customizing, do you think he'd be posting this question here? I've been working on these trucks for over 15 years, and I'm not at that level, even if I thought it was worth the effort. Currie has been designing their own 9" housings for years, and I'm not sure they've managed to add a VSS to one yet. But check their website...An '80-86 F-series/Bronco 9" would bolt in - no mods necessary. Maybe '78-79, too. At most, the pinion yoke might have to be swapped to a companion flange, if his '91 has that setup now. But it's even easier to remove the mating bracket & just attach the '91 u-joint to the older yoke.Haha is right: it depends where the axle breaks, but I've been working/wheeling an 8.8" for a long time, and I've never broken a shaft. That includes when I towed a Peterbilt dump truck and exploded the pinion yoke. There were a few 9"s that broke at OCBR last month, and one lost a wheel. Another broke the tube off the housing.

. .

...and those were all under early Broncos (VERY light vehicles).That's more different than it seems. An Ex can use a weaker axle since it's a lighter vehicle with a weaker (stock) engine. And the Ex disk brakes fit the 9", but they're not big enough for a 1/2-ton, even if the lug spacing was right.

 

I disagree with your second sentence here. The 9" because of it's wide use in all forms of motor sports has huge after market support. Every single part of it can be upgraded, the 8.8 just doesn't have this. The 9" can be built to the point where it rivals a stock one ton axle and fit in a smaller package.

I will give you this however. The stamped 9" center section is a weak point that the 8.8 doesn't have. Wouldn't surprise me if that's where the difference in rating comes from.

I don't know what level he's at. Looks pretty easy to to do to me. And just cause Currie may not offer something doesn't mean that it's not possible.

Heres a couple options:
http://www.breaautoelectric.com/products/products1.html

http://www.race-dezert.com/forum/sho...ion-help/page2

Agree, if you break the 9" shaft off at the flange you're in for a rough ride. I've seen plenty of 8.8's break...and i've seen plenty of 9"s break as well. No axle is unbreakable though haha.

I wouldn't use an eb9" they are weak in comparison to a 8.8 or full size 9". I have seen 8.8's break where the tube meets the chunk as well. Plug weld breaks, the tube spins you're day is over. In fact a guy at my last run who had an eb blew his pinion. That day I don't remember any 8.8's breaking but he was bouncing the rig...pretty much a recipe for a break haha.

My explorer weighs in around 4500-5000 lbs. The front and rear axle are both out of 78 f150 and have not been cut down. The engine is a bit weaker yes but I run 35"s and 5.13 gears so there is a good deal of torque running threw them. And I know that if I start to break my 9" there is a stronger part on the market....just depends on how deep my pockets are. I did not build it for mudding or driving down gravel roads. I built it for hard trails, rocks and anything else I can find. The result is a rig that is much much more capable than the driver is (me). After exhaustive research the 9" was the best option for me because of it's strength and after market support.

Instead of using explorer brakes (which may or may not fit actually) throw dana 44 rotors and gm calipers on it or any other caliper you want. Lug spacing is easy to work around. Either use a full size rotor with the correct pattern or re-drill one. For a full size I would agree the explorer stuff probably isn't big enough.

I'm not trying to get into a pissing match or anything. The 8.8 is a great axle I have no issues with them. Depending on what the op is wanting to do the 8.8 very well may be the best option. If he wants something to put in with no issue...8.8. If he wants something he can upgrade to the sky until his checking account is empty...9".

 

You haven't shopped for 8.8" parts in the past 5 years, have you? And many of the 8.8 upgrades can be had from junkyards because of the wide variety of stock applications.Not a chance. Not even halfway there. Not even an old (70s) 1-ton axle. Here are some 8.8 & 1-ton ratings:



The 9" was rated 2700~3300lbs. You'll never get it to carry over 4Kip reliably. Its housing just isn't strong enough, even if you truss it.No, it comes from the tubes, axleshafts, & wheel bearings (cargo capacity), and the strength of the gears & diff carrier (towing capacity). Then they upsized the brake shoes from 1.75" for the 9 to 2.25" wide for the 8.8 to correspond to the increased GCWR. And with disks, some 8.8s are rated even higher. For a few years, the 8.8 was used under the Expedition with thicker axleshafts & bigger brakes.True. And just because NASA may not build something doesn't mean it's not possible. But Currie is the acknowledged industry-leader & innovator when it comes to the Ford 9" axle, and there IS a market for a 9" w/VSS, so why don't they sell one? If they do, check out their price - if there was a cheaper way that worked, wouldn't they offer it?I hear that a lot, and I've seen pics of Mustangs doing it, but I've abused mine severely, and often, and that's never happened to me. I've broken a few 8.8s, but never like that.Are you sure about that? Have you driven over a certified scale? I have in a stock '93 FSB 5.8L E4OD that weighed 5240#. Mine, with bumpers/tools/full gas tank is 5990.Torque doesn't come from the tires - it comes from the engine/trans.Me either - I'm just discussing the pros & cons of the axles, and the issues relating to them - nothing personal.

 

Remind me to never argue with Steve..
But really why would anyone waste their time upgrading to a 9"?
You can get anything you need for an 8.8 from a junkyard or very cheap online.
Just seems like common sense to me.

 

Who's arguing? We're just discussing.

 

I swapped a 9" into my 87 Bronco after destroying the limited slip and then later smashing the cover in the 8.8 axle. The 8.8 axle is a fine unit, but between getting rid of the c-clips, and being able to swap out a damaged housing without having the gears setup again, and wanting to go to disc brakes I chose the 9". The pinion gear in the 9" is also supported with a third bearing making it stronger than the 8.8 gear set. The VSS in the 87 is in the tcase, so no problem for me there.

I originally got one of the 78 Bronco housings with the plug welded tubes. I kept the drum brakes initially and it was basically a bolt in swap. in 2004 I built a full welded housing out of an 84 Bronco to go with my rear shocks and disc brakes in 2004. Running 35" tires on a trussed 9" I have had no issues, and the truck gets used hard.

 

That's backward. The 9" needs 3 pinion bearings because it's weaker than the 8.8". Look at cutaways of each and you'll see how close together the 9" main pinion bearings are - too close to hold it straight under any load, which is why they added the rear bearing. The 8.8's bearings are ~2x as far apart, and its shaft is thicker, making the 8.8 stronger. That's just another reason Ford rates it for more load than the 9. If the 9 was better, Ford wouldn't have replaced it with the 8.8 .That VSS is for cruise & the E4OD transmission. The one for ABS is always in the rear axle, and on '92-96 trucks, the one in the rear is also used for cruise, transmission, & more.

 

Ok guys well thanks very much. I just perfur the 9 inch rear end, had one in my 73 that never let me down in 400,000 miles! I dont put much weight in the bed, I tow what ever I cary thats large, so I have decided to use a early bronco 9 inch rear with traction lock and fit it with disc brakes! Once again lots of information and as always a big help!

 

That won't work. An early Bronco is much narrower than an F150.