Nothing Special's '71 Bronco

[Nothing Special]

Gary Lewis wrote

If it goes under the Atlas to be the skid plate then I think it has to sit lower than if it is just reinforcement.  So what if it was two parts - the one I show that is wider than the frame rail by ~2", and a skid plate that bolts onto that with spacers that drop it down enough to go under the Atlas.

The ~2" lip, sticking in, is to bolt to.  But that also means it'll have to go lower than if it was just the width of the frame.

On the other hand, if the strap was just the width of the frame but was thick enough I think you might get by with two holes in it to bolt to.  That would minimize the drop in the strap, but then you'd have even more of a need for spacers to get the skid plate under the Atlas.

I really appreciate the different ideas, and now is a good time to get them out.  But I'll warn you that I'm not going to put much more detailed thought into it until I get closer to actually building it.  Right now my mind's moved on to getting the axle out, getting the radius arm mounts back to stock and getting the new axle modified and in place.  Then after I have it sitting on its own tires again I'll get back to the skid plate and reinforcing the frame.

That said, I will think about it a little more now.  I'm envisioning the skid plate being tight against the bottom of the fame rails to maximize ground clearance there, and dropping down as needed to clear the transfer case.  Of course I also want smooth transitions on the bottom of the skid plate so it doesn't act as a grappling hook, grabbing hold of every rock it touches.  So we'll see if what I envision ends up materializing.  But if it does, the skid plate will be close enough to the frame rail to be the reinforcement (whether it can be attached well enough to be the reinforcement is a different still unanswered question).

[Nothing Special]

... and yes, in the post above I did say "new axle."  Because even though I previously said...

Nothing Special wrote

....  By the way, doing all of that to the front axle begs the question "why not switch to a high pinion diff?"  I've thought about that, and while it would be good for U-joint angles, driveshaft clearance and gear strength, "they say" that you need at least a 4" - 6" lift to get a high pinion diff to clear the oil pan.  Lesley doesn't want the Bronco to be any higher so that much lift isn't an option, so I'm sticking with the low pinion....

... I'm going to try to put a high pinion axle in it.  In more conversations on an early Bronco forum I've now heard that 3.5" lift is enough for a high pinion, and I'm pretty close to that.  Also I've heard at least once that it's the oil pan of the C4 automatic that's the issue, not the engine oil pan, and I don't have a C4.  Looking at what room I have I can't imagine I'm going to have trouble with any interference with the oil pan or the NV3550 trans.

So today I got these:


I really only wanted one, but the first axle the junk yard pulled had water in it so they stripped it down to find out what it looked like inside.  The gears were rusty, so they pulled another one.  That wasn't the right one* (fortunately I talked with them before they shipped it) so they found another that was correct and said they'd ship that.  But since I had told them that I really didn't care if the gears were rusty I guess they decided to sent the first housing to me as well.  Anyway, I got everything i expected and more, so soon it will be time to start putting a high pinion axle together!


*  And on "the right one," Up through 1975 F-100s and F-150s (if 150s existed yet) had drum brakes in front.  In '78 and '79 they had cast axle tubes that had the wedges integrally cast with the tubes, so you can't cut them off and weld them back on.  So '76 and '77 are "the right years" to get.  You get all of the parts needed to put disk brakes on and tubes you can more reasonably modify.  Plus I think the '76 - '77 are the largest diameter, thickest wall tubes, so you also get the strongest housing.

And yes, even though I already have disk brakes on my stock axle, I need new parts for this one.  My Bronco came with drum brakes, and the easiest way to convert to disks in front is to use a combination of aftermarket parts and parts off a Chevy truck.  While I might be able to put my old knuckles on the high pinion Cs, using all '76 - '77 F-150 parts makes for a simpler system.  And it also gives me stronger outer axle stubs than the '71 Bronco parts.

[Gary Lewis]

Cool!  I'm subscribed.  Now where's that popcorn-eating emoticon...

On the frame/skid plate, I think it is good to get several ideas in mind up front and then you can think about them as the project progresses.  Sometimes things will fall into place and you'll said "Yep, that will work."

[FuzzFace2]

I was talking of boxing in the opening to the inside of the frame making like a pocket the case would fit into like it dose now. Think of it like the 460 oil filter notch on the frames to clear the filter but a little more square. I think this would add back some strength to the frame.
Then the skid plate from side to side to add more strength.

Not knowing just what you have going on there on the skid plate & edge of frame maybe you could add angle iron welded to the outer edge (could point down) that maybe the bolts would go through as that should also add strength.

The Jeep YJ mounts the trans / transfer to the skid plate that runs side to side and is bolted to the bottom of the frame. The only thing they did wrong was use nut certs and years later when you have to drop everything the nut certs would spin so you would then need to cut the bolt(s) off and figure a way to bolt the plate back on.

How do I know this you ask? My son went through this on his.
I also told him once the nut certs were out to make the holes bigger so a normal nut would fit in the hole and weld it in place. Then when putting it back together to never seize the bolts.
I think he only did 1 like that dont remember what he did on the others?
Dave ----

[Nothing Special]

FuzzFace2 wrote

I was talking of boxing in the opening to the inside of the frame making like a pocket the case would fit into like it dose now. Think of it like the 460 oil filter notch on the frames to clear the filter but a little more square. I think this would add back some strength to the frame.
Then the skid plate from side to side to add more strength.

I'm definitely planning on that.  Stealing Gary's sketch from a few posts back, I'm planning on welding small plates at the top and sides of the cut-out (all three of the thin black lines).  Those plates will be welded to the cut edges on the inside face of the frame and to the inside of the outer face, as well as to each other where the top and side pieces meet.  I might also weld a vertical plate in from the bottom of the cut up to the top piece I will add.  But I agree with Gary's point that all of that won't entirely make up for what cutting the lower flange lost.  So hopefully I can figure out how to do that with the  skid plate.

FuzzFace2 wrote

Not knowing just what you have going on there on the skid plate & edge of frame maybe you could add angle iron welded to the outer edge (could point down) that maybe the bolts would go through as that should also add strength.

I'll file this with ideas to think about when I'm back to thinking about this.

FuzzFace2 wrote

The Jeep YJ mounts the trans / transfer to the skid plate that runs side to side and is bolted to the bottom of the frame. The only thing they did wrong was use nut certs and years later when you have to drop everything the nut certs would spin so you would then need to cut the bolt(s) off and figure a way to bolt the plate back on.

How do I know this you ask? My son went through this on his.
I also told him once the nut certs were out to make the holes bigger so a normal nut would fit in the hole and weld it in place. Then when putting it back together to never seize the bolts.
I think he only did 1 like that dont remember what he did on the others?
Dave ----

Yeah, I won't be using nutserts!

I don't want to use the skid plate as the trans mount crossmember.  I want to be able to take the skid plate off without worrying about supporting anything else.  I've definitely seen it done that way, but it's not what I want to do.

[Bruce moose4x4]

I read your not thinking a whole lot on strengthening the frame But I wanted to give you my thoughts.
Cut a heavy piece of angle or another section of frame. make it long enough to span the hole you cut out, I would make it as long as you could to go inside the frame rail with the back towards the outside of the frame and along the bottom of the frame. Drill or cut some holes in the outside of the frame and along the bottom and plug weld the angle to the frame. once ground down on the outside of the frame no interference with the side tank. You might have to radius the corner of the angle iron to get it to fit snug against the interior frame wall. That is why I mentioned using another piece of frame rail that has the radius. If you need a piece I have some old frame rail pieces laying around I could cut to your size and send you.
Looking forward to seeing the conclusion of this build. If you ever get back to SMORR let me know, I only live 30 miles from there.

[Nothing Special]

I'm not quite following you.  Are you talking about putting steel inside the original frame rail?  If so, that sounds challenging, and I'm not sure it buys me anything.  I've got room for a plate on the outside, just probably not for a C-channel with the opening to the outside.  And what I need to do is replace the beef I had to cut out of the bottom flange.  But I can't do that by just putting new metal there, I need the cut-out for my transfer case.  So I'm thinking something like Gary sketched will be my best bet.  Then it's a question of how to integrate that with the skid plate.

[Bruce moose4x4]

16504176274521555276090.jpg

Yes an angle inside the frame rail plug welded like you did your rock sliders. With the angle inside would create no interference issues. You could then box the hole you cut like you planed.

[Bruce moose4x4]

The pic is not rotated correctly. Did that on my phone, But maybe it will be a little clearer.

[Nothing Special]

Thanks for the picture.  It's definitely good to have more stuff to think about.

[Nothing Special]

Nothing Special wrote

....  I really only wanted one, but the first axle the junk yard pulled had water in it so they stripped it down to find out what it looked like inside.  The gears were rusty, so they pulled another one.  That wasn't the right one* (fortunately I talked with them before they shipped it) so they found another that was correct and said they'd ship that.  But since I had told them that I really didn't care if the gears were rusty I guess they decided to sent the first housing to me as well.  Anyway, I got everything i expected and more, so soon it will be time to start putting a high pinion axle together!....

Good thing they sent both.  I didn't pay very close attention when I was loading them into my truck at work.  I needed to get them out of the way and get back to my job.  But when I got them home I realized that the complete axle is a '78 - '79.  I can't use that housing, but the spindles, brakes, hubs and outer axle stubs should all work with the '77 housing.  So I should have all the parts I need to put one axle together and a heavy piece of scrap to get rid of eventually.

[Gary Lewis]

Sure glad you got both axles!  

[Nothing Special]

The fun with the squirrels in my motorhome air intake took up most of my project time this weekend.  But I did get back to the Bronco for a little bit.

My main progress was getting everything I need pulled off the '78 axle housing.  That also made me hate Minnesota road salt all the more.  Every time I've pulled the spindles off a 4WD front axle for the first time they've been ridiculously rusted in.  Once I get them out I clean them up and use anti-seize, so they usually come apart for me fine after that.  But on this old axle I was expecting a fight.  But this axle wasn't from Minnesota!  Both spindles came off pretty easily!

Actually the worst thing I had to deal with was getting one of the brake calipers off.  A previous owner had laid a weld bead along the top edge of the caliper bracket.  I wasn't able to get the caliper off.  It wasn't welded in place, but the weld bead didn't leave enough room to get it out after I removed the retainer.  (I don't know how he got it in...)  A little touch with a cutoff wheel in my angle grinder gave me the clearance I needed.  Hopefully I won't have any trouble putting it back together.

The only other thing I accomplished was getting the front of the frame supported on jack stands so I'll be able to remove the front axle.

[Gary Lewis]

I mentioned to my brother recently about the road salt and the cancer it creates.  I don't think I could deal with that!

So I'm glad you got things apart fairly easily.  Sometimes things go a lot better when you've gotten things apart, cleaned, and ready to go back together.  Let's hope that's what you are going to experience next!

[Nothing Special]

I still have a lot of disassembly to do before I'm putting things back together!  The worst (best?) of which will be cutting apart the '77 axle housing to move the wedges, inner C's and track bar mount!

[Nothing Special]

Some more disassembly this weekend, much of it using a cutoff wheel, but I still haven't started cutting the axle housing apart.

First was getting the Bronco axle out.  If I was working on a lift that would have gone pretty well.  But crowded against the wall of the garage makes for less comfortable positions.  So after that I was done for the day.

Then Sunday I cut the dropped radius arm brackets off!  Getting rid of them was the impetus for this whole snowball.  So now I'm done with the main project, I just need to clean everything up!  OK, not so much.

Anyway, cutting the brackets off went pretty well.  I went through six cutoff wheels, which was all I had.  But I was able to do it without cutting off the stock mounts, so I don't need to put new mounts on like I was expecting!  I ended up leaving a lot of the drop bracket metal in place where it's not in the way, so it will even reinforce the stock mounts.

Now I need to pick up more cutoff wheels so I can get started on the axle housing!

[Gary Lewis]

Sounds like you are almost done.  Done cutting that is.  

Glad you could save the stock mounts - that should make things easier.

[Nothing Special]

Yeah, I wasn't looking forward to putting new radius arm mounts on.  I've welded to this frame twice before, building the front bumper and putting the dropped radius arm mounts on.  I don't know what it is, probably the steel alloy the frame is made of, but it's really hard to get a good arc.  Of course I still need to weld on the frame to reinforce where I notched it for transfer case clearance, but at least I don't need to do as much of it as I expected!

[Gary Lewis]

Be thankful for small wins.  

[Nothing Special]

Well, I'm getting closer to being done with the cutting!

But first a picture from last weekend's work.  The first picture is one from when I was notching the frame.  It shows the dropped radius arm bracket in the foreground.  The second is after cutting the dropped mounts off last weekend.






OK, on to new business.  Here's a "before" picture.  The "new" '77 F-150 axle is in back with the "old" '71 Bronco axle in front.



After about 7 hours, 7 cut-off wheels, a bunch of work with an air chisel and a lot of swings with a big hammer the high pinion axle now looks like this!



The wedges weren't too bad.  The inner C was in the way so I couldn't cut them all the way off with the cut-off wheel, but I could get most of it, and then had to finish up with the air chisel where the wheel couldn't reach.

The inner C's were another thing entirely!  The wedges were in the way to get at the C's worse than the other way around (which is why I took the wedges off first).  I started on the passenger's side because I'll be cutting 6" off that end of the tube, so if I screwed it up it wouldn't be so bad.  Then after practicing on that side I hoped to be able to do the driver's side more confidently.  The problem with that plan is that I couldn't get the passenger's side off!

Eventually I gave up and cut the tube off flush with the inside of the C.  Then I could use a hack saw to cut through the section of tube that was left in the C.  I made 4 cuts and was able to knock the 4 sections out with a big hammer and a punch.

Doing that I realized that I hadn't cut into the C enough to get past where the weld had penetrated.  I still wasn't at all sure that I could do the driver's side, but I did try to cut back into the C a lot more than I had the first time.  I didn't have a lot of hope when I started swinging the hammer but, to my surprise, a line started opening up!

I still need to clean up the OD of the tubes and cut both tubes to length.  Then I'll be done cutting things off!

Don't worry, I'll still have use for my cut-off wheel.  I'm going to have to fab up two bump stop mounts for the axle (one will also include the track bar mount).  And near the end of the project I'll be making the skid plate.  But I am pretty close to starting to put stuff back together!