Narrowing truck 9 inch to 77 bronco size

[broncochevy]

Okay, I have a 1972 F100 rear end with large center section, 31 spline axles, 11 x 2 1/4” breaks, and large bearings. Is it possible to narrow it to the width of a 1977 bronco rear and use the “stock” bronco length axles (if a replacement would be needed) and even cut and respline these truck axles to bronco size? The reason I want to do this is threefold, it may be cheaper than a totally new housing, and it would be an upgrade from the small bearing 9 that I have already for my bronco, and I have this rear already. It has the ratio I want and it looks to me like a wider version of a 77 bronco rear with the same size brakes. I searched and found threads with “holes” in them as in they weren’t totally finished or not much explanation. I do know that at one time narrowing 9 inch rears was commonplace especially in the hot rod scene. Searched in those types of forums and found that those guys use early bronco rears in their rods as they don’t need narrowing because they are the perfect size. Just wondering...as my budget isn’t exactly like that of a coyote bronco build. Naw mean??

 

[nvrstuk]

Yes, like you said it is common to narrow the axle housings, however re-using the 31 spline axles that come with the truck rear end assembly probably will not work because you will not be able to re-spline the axles after you shorten them to fit the "new" WMS-WMS dimensions. I believe (90% certain) that the axles on that year truck setup has a taper in them and you wouldn't be able to re-spline them after cutting them to the proper length. (Someone will chime in with 100% certainty)

You could reuse your existing 28 spline stock Bronco axles if you buy new Torino ends (available at dozens of suppliers) after narrowing the new truck housing to your Bronco width but of course you'd have to re-use the Bronco 9" carrier assembly since it is setup for 28 spline axles.

 

[sykanr0ng]

It can be done, but if you do not have the jigs and fixtures for it and / or are not a really good welder then you should find one of those hot-rod shops.

I have been looking at having a shop attach different ends on a Bronco housing (for disc brakes) without narrowing it and it would cost me at least as much to buy the jig and fixture as having the shop do it, so unless I set up a business doing it I would hire it done.

 

[Timmy390]

I didn't narrow my housing but I did replace the ends without a jig. I don't advise it but it worked for me.

We took lots of measurement prior to cutting. We welded the housing to a 2 post car lift so it wouldn't move but we could raise and lower the housing as needed.

We cut one end at a time. We left the center section in and used the old axle and bearing as an alignment tool. With the new end in place and measurements confirmed, we slid in the axle and check measurements again and then welded it up. Repeated the process on the other side. The bearings were toast after due to the heat. We installed a 31 spline center section and axles after it all cooled down.

It's been 3 plus years now with no issues........I got lucky I guess.

Tim

 

[Boss Hugg]

my experience

http://classicbroncos.com/forums/showpost.php?p=2985864&postcount=1

 

[Jedeka]

Check out Quick Performance. They have been selling 9” parts for years.

 

[Boss Hugg]

Check out Quick Performance. They have been selling 9” parts for years.

That's where I got my ends. But if I do it again, i'll study more on the actual diameters and get a set that fit my tubes better. I think they have several options, but it's been a while now...

 

[Timmy390]

That's where I got my ends. But if I do it again, i'll study more on the actual diameters and get a set that fit my tubes better. I think they have several options, but it's been a while now...

Bought my ends off ebay and had to have them turned to fit my tubes. A pain but in doing this I was able to keep things very snug which helped with the alignment.

Tim

 

[Boss Hugg]

Bought my ends off ebay and had to have them turned to fit my tubes.

mine came from ebay as well, but Performance was the seller. Can't remember their user name.

 

[Broncobowsher]

For the most part the current housing ends are scrap. New ones that are clean and true are widely available. It is possible to reuse the old housing ends but to do it right would be chucking them up in a lathe and cutting the old weld and housing away. In the end you still have and old housing end that has already had 40 years of abuse and neglect, corrosion, etc.

Next up is the alignment. There are jigs for this. If you are going to do this a few times it is probably worth getting the tools. If this is a one time deal, have someone else do it.

And I didn't think that the 9" in the trucks came with 31s until the mid 70s. You might have a 28 spline full size axle.

 

[Apogee]

I put new ends on a '76 F150 housing and used new housing ends from Quick Performance ($65/pair), a Mitler Bros alignment bar/pucks, and burned it all in with a nice HD welder. The effort to narrow it and match the EB width and pinion location wouldn't be much more. That said, by the time you buy the tools and new housing ends, you're probably over the cost of a replacement housing.

The aftermarket housing end are not intended to be inserted into the tubes, as odds are the housing isn't straight anyway. When I installed the alignment bar through my housing, I found that the tubes were out by about 3/16" on on side and a little under 1/8" on the other from being straight and true to the differential bearings. I performance a nice full penetration butt weld and now my housing is true to within 1/32". I tacked the housing ends at quadrants with heavy tacks, and then welded them out one quadrant at a time, working criss-cross to minimize distortion due to heat...seemed to work.

I thought all of the F150's from 73-86 had 31-spline axles, whereas only the F100's with single speed transfer cases came with the 65" wide 28-spline units, although I could be wrong about that. It's been my experience that Ford has a way of kicking you in the nuts whenever you think you've figured something out to be "true".

 

[SteveL]

If you're not set up to do the work it sounds like a money pit. There are some sites you can buy a floater 9" set up in the $700 range. Not sure if that included brakes. When I was looking I ended up finding a 77 housing with moly axles for 400. Then added bc disc brake brackets. Got the rest from napa

 

[broncochevy]

No definitely 31s. I counted them a few times. This F100 was bought new by my grandfather with a 360 FE V8, C6 and heavy duty springs. Don’t know if that warranted a heavyweight rear end or if they all were like that?
So, the breaks are 11” diameter drums and 2 1/4” pads, are these the same as a 77 bronco rear? Pretty sure they are. The offset the breaks provide is 2 1/2”. Let me know if I am wrong...
So if the WMS to WMS demension should be 58”, then my housing needs to be 5” less (break offset x2 for each side) giving me 53” from housing end outside to housing end outside. Does this seem correct? Is there something I am wrong about, because I believe I’ve read here that that measurement should be 52 5/8”?? I called WH and TBP, and WH confirmed this measurement. TBP had me get the other measurements making sure my break offset was not going to change my track width. Both were helpful, because I did explain how I was most likely going to need axles and other things mom, plus so much other stuff for the rest of the bronco. Also called JBG and was explained to that they just sell things, not this sort of help, which I do understand, maybe I don’t need anything from them from now on.
And yes, I am not going to do this myself, I don’t have the means. But the housing is tapered at the end down to the ends. They may have to cut it on the other end of the tube, but I am going to leave it to a pro.
Thanks for all the responses and help,

 

[broncochevy]

One more shot

 

[garberz]

How much money are you saving by cutting down this old F100 9”? This Currie 9” from WildHorses is tough to beat, just over $500 with tax. It’s new and much stronger than the old stock 77 9’s. I think for just a little more money, you could go with something new. My .02.

https://www.wildhorses4x4.com/product/Super-9-Housing-66-77-Bronco-Large-Bearing-Large-Bolt/Bronco_Rear_Housing


Mark

 

[DirtDonk]

Thanks Mark. And sorry we had to raise our price.
But the good news is that it's back to the old price AND free shipping this month!

WH Heavy Duty Super-9 Housing

I had forgotten that, but when I clicked on it had a not-too-subtle reminder.
But I understand if you already have one housing the desire to do it yourself. Totally.
And if you have the time, it can be worth it. But if time is money and you can sell your existing full-size 9" to someone to help offset the costs, at least it's worth doing some factorin' & figgerin' to make sure.

The other downside to all this "adding-for-dollars" is that new axle shafts are not that expensive either. At $250 for the pair of high-strength alloy, Set-20 bearing equipped 31 spline shafts, it's not a lot.
But when you start adding things up, you're probably still better off initially doing your own.
But you said you'd probably have a pro do it? I'd get quotes then if you haven't already. When all is said and done that kind of stuff adds up quickly too.

Some of the full-size axles can be cut and re-splined. I have a set in one of my housings as well. But I would never do it without re-heat treating, or cryo treating them. The splines on these twisted up faster than you can say BroncoRangerExplorerSport! It's not pretty...

And the cutting and re-splining is likely not inexpensive anymore either. It used to be a perfectly viable way of saving money over new. But at 250 plus shipping, I bet you're going to be in to the axle shafts for more than brand new.
But if you find an old school shop with the old timer that doesn't have to prove anything to his wife working it, you may actually get an old school price too.

It's all up in the air. But definitely get some quotes in case you decide you want to take advantage of some sale pricing.

Good luck!

Paul

 

[broncochevy]

Thanks for the advice, all of you. I so far haven’t found anyone to do the work, so quotes at this point are a no go. I am trying to bring back to life an old military bronco, that was rolled 30 years ago, and with one income, 2 little boys and a house payment on the central coast of California, any money saved would be appreciated onto the next part of the build. No coyote install here, no high pinion nothing. I may be cheap, but I do know the value of a dollar, and I can make it last. Plus Christmas and the holidays are coming fast, and the only one who wants bronco parts in this house is myself. I just thought if I could save $200-$300 off a new housing, I could justify the little extra on some axle shafts.
Paul you are right, I think that is a good price for new axle shafts. I don’t know if you were the one I spoke to on the phone, but WH was helpful to my about this issue. I don’t know everything about the issue at hand, and your guys helped. Thanks. Toms didn’t turn me away either, however another vendor was unwilling to help to say the least. If my “poor” money isn’t good enough, then it doesn’t need to go there.
My late grandfather was born in 1920, was raised thru the Great Depression, and never threw anything away. What he didn’t have, he made. With an old Allis Chalmers stick welder and his hands. He actually rolled both of these vehicles, years apart, on his ranch. He purchased the truck new, and got the bronco from a, what he called a junky, but not the drug kind, in Barstow, California when the bronco was 11 years old in 1978. My family’s love for broncos began then, we’ll probably before as my father wanted one but never was afforded the chance. This 72 f100 was bought for him. “You need a pickup, not a bronco”. The just thought I could blend the 2 vehicles together beings I had the rear already, but I need to find someone to do it first.
Thanks

 

[SteveL]

It wasn't a 77 but I think there was a complete working eb rear end in the classifieds. I think it was here in LA

 

[DirtDonk]

That's a great family story James. Hopin' it will all work out with the family budget. I know about saving everything and building what you can't save too. Unfortunately the current digs don't have much "redneck room" on the front lawn for truck parts!

Good luck with it.
I forgot to touch on the advantage of doing it the other way. I was pointing out the obvious "potential" savings of buying some new stuff (and hoping it was from us too of course!) which is perfectly legit and may indeed save you money over time.
But the angle I didn't take into account then, but often use it myself, is that it may cost me more to do it myself, but it costs less "per purchase" since you're only buying small stuff at first.
So either way works for me! Just let us know what you need and we can usually figure out some recommendations.

Good luck.

Paul

 

[68ford]

By the time you pay parts and labor, you could pay for most of a floater kit.
Brand new housing any width you want, hubs, bearings, seals, drive plates, axles and brake rotors for 850.
Use your 3rd member and buy a set of common oem calipers. Sell your old parts and you will be all new for 700ish.
http://9inchfloater.com/CompleteRrEnd/CmplteRrEnd_28_31.htm