Measurement between frame and axle housing??

JSmall · Oct 30, 2015

I've always read that a stock height Bronco will have 7 inches between the bottom of the frame and the top of the axle housing in front and 6 inches in the rear. Using one of the frame drawings that I found on here, I verified the frame heights have the same dimensions front and rear (see pic, red line).

I'm crunching numbers for my 4-link right now and I want to make sure I setup the front and rear with about 4.5" lift and the starting distances are important to get it correct.

I am looking at this correct? I don't want to set my front axle at 11.5 inches and my rear at 10.5 inches (4.5" lift) if that is not accurate. Should both be at 11.5 inches?

Crush · Oct 30, 2015

Dont see where you are getting the fram to axel measurement off that pic? But 7 and 6 have been the norm for figuring out how much lift you have.

JSmall · Oct 30, 2015

If the frame is level and the distance to the ground to the frame is the same front and rear, why would the distance from the frame to axle not be the same? I could be missing something here.

**Edit**

The red boxes in the pic are the same length.

Apogee · Oct 30, 2015

Good question. That said, the axle tube diameter is different front to rear by 1/2", so there should be at least a 1/4" difference based on that alone since the measurement is to the top of the tube, not axle centerline.

JSmall · Oct 30, 2015

Apogee said:
Good question. That said, the axle tube diameter is different front to rear by 1/2", so there should be at least a 1/4" difference based on that alone since the measurement is to the top of the tube, not axle centerline.

Now to figure out where the other 3/4" comes from

Action · Oct 30, 2015

I would look at it like you are but like you have always heard the 6 and 7 inch deal.....wondering myself now.
Jack

jckkys · Oct 30, 2015

Every new Bronco I've seen, including the two I bought new, had a slight nose down stance. The '77 had/has the front sitting about 1 1/2" lower than the rear. This seems to contradict the common definition of stock ride hieght of 7" front and 6" rear. My '77 sits about 1 1/2" higher than that, front and rear, with stock springs. The rear end sits the same 1 1/2" higher than the front, as it did when new. A level stance was never "stock". If the frame blueprint indicates the front end should be higher than the rear, the reality is the opposite. The 7"/6" thing never carried much weight for me. It was clearly a vague guess at best. Different equipment and GVW packages resulted in a range of ride heights.

DirtDonk · Oct 30, 2015

What he said. I use it as a general reference to get people in the ballpark when trying to figure out what lift they might have, or what to expect when they install a new lift. But it's not etched in stone and is definitely approximate.

And also like said, not all Broncos sat with the same rake right from the factory. Although I've seen some that were (or at least appeared) perfectly level, by far most had a slight up in the rear stance.

I'll continue to use the 7 and 6 as a starting reference point, but if someone comes up with a better generalization, I'm all for it.
Never even measured my own, but with no engine and nothing in the back currently, it's not much of a reference.

I could wander around the shop and get measurements from stock and modified rigs, but now with 40+ years on them anyway, it'd be hard to call that an exact science either.

Paul

Steve83 · Oct 30, 2015

jckkys said:
...the front sitting about 1 1/2" lower than the rear. This seems to contradict the common definition of stock ride hieght of 7" front and 6" rear.

You all seem to be forgetting that the frame is NOT horizontally straight. It arches above both axles.

And my diagram in post #3 is ONLY for the frame; the circles I sketched in for the axle tubes are NOT based on any measurements I took. So the red boxes prove nothing other than my arbitrary placement of those circles.

THIS is (apparently) based on Ford's designs:

That diagram indicates that the frame arches 1.19" (1 3/16") higher above the front axle than the rear, which is why the front frame-to-axle measurement is larger, even though the factory ride height was essentially level. It's also worth noting that that diagram references the normal TOP of the frame, and you're all talking about the BOTTOM of the frame. So the frame's height becomes relevant to your discussion, and it varies front-to-back.

And this is (probably) based on Ford marketing literature:

I just cleaned it up & applied the measurements to another diagram I was working on, just to make them easier to read. I didn't confirm any of those dimensions - I just copied them.

JSmall · Oct 31, 2015

Thanks for the clarification Steve. I'm on my phone right now so I'll have to look at the picture when I can get to a computer.

The first picture that I attached is the side view of the frame and if a horizontal line is drawn between the two frame locations, they are level. I think that is where my confusion came from. I will use the original numbers now after your explanation.

Steve83 · Oct 31, 2015

The first one is just my version of an older diagram that I cleaned up & corrected some REALLY obvious errors. The diagram itself is low-resolution (meaning the contour of the drawing is not necessarily an exact match for the contour of the frame), and not necessarily presented at ride angle on level ground. The larger diagram of every surface of the frame SHOULD be vastly more accurate because I created it from scratch using a laser level. But it's still not necessarily at ride angle (just an angle that I chose to make my measurements easier), so it's not useful for measuring body or axle positions - strictly the frame. And I just measured an old frame that ended up in my possession - I can't say for sure that the frame I measured was still in factory shape, but I didn't find any signs of bending, so it's the best diagram of its type available right now. When someone 3D-scans an eB frame & uploads it, that might show some defects in mine, or at least DIFFERENCES.

JSmall · Oct 31, 2015

Thanks Steve

bronconut73 · Oct 31, 2015

Steve83 is da'man, here "and" at FSB.

jckkys · Oct 31, 2015

For those of us who saw many more new Broncos than modified types, the idea that stock ride height or stance was level, is laughable. Just look at some photos in the contemporary road tests. None of the above diagrams is accurate in this respect.

JSmall · Oct 31, 2015

jckkys said:
For those of us who saw many more new Broncos than modified types, the idea that stock ride height or stance was level, is laughable. Just look at some photos in the contemporary road tests. None of the above diagrams is accurate in this respect.

I'm not so much interested in what the stock stance was (nose high or low). I'm going with ORI struts so I will be able to level mine out when that time comes. What I'm trying to do is set my axles at ride height so I can measure for links. If level is one less inch in the back, I want to take that into consideration when I'm building.

Steve83 · Nov 1, 2015

bronconut73 said:
Steve83 is da'man...at FSB.

%) Not so much...

bronconut73 · Nov 1, 2015

Steve83 said:
%) Not so much...

OMG F'n wow.....
I still learn from your threads over there.

Mark · Nov 2, 2015

Steve83 said:
%) Not so much...

must be a mistake

Measurement between frame and axle housing??

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