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9" rear end newbie question

1967Bronco

Jr. Member
Joined
Mar 7, 2012
Messages
65
I have the stock 9" rear end from my 1967 bronco. What are the issues with swapping in a newer 9" big bearing from the 70's? Any major mods needed?
 

Pedestrian

Bronco Missionary
Joined
Sep 10, 2008
Messages
2,299
Are you wanting to go wider because the fullsize 9" is about 6" wider.
 
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1967Bronco

Jr. Member
Joined
Mar 7, 2012
Messages
65
I wasnt looking to go wider. Sounds like it wont be a simple or exact swap out.
 

thegreatjustino

Contributor
Red Head Grease Monkey
Joined
Jan 23, 2002
Messages
15,620
Loc.
Stockton, CA
Rear end is easier than the front end. In the rear, you'll need to move the spring perches and shock mounts inward so they line up with the EB frame.

You are planning on swapping to a full size front end at the same time right? That's a whole different headache.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
OK, sounds like he wants to swap in a big bearing EB 9" into his small bearing '67. Shouldn't be so quick to assume he wants to do a full width swap.

All early bronco 9" axles from '67-77 are a bolt in interchange. The '66 has different shock mounts due to the forward facing shock mounts in that year.

Couple of things to watch for are brakes and gear ratio. The gearing has to match between the front and rear axles. Stock 9" ratios are 3.50, 4.11 and 4.56. The front axle is 3.54, 4.10 and 4.56. 3.50 and 3.54 are considered the same, 3.50 and 4.10 are not.

Brakes, as long as you get the big bearing 9" drum to drum you are fine. The brakes are completely different between the small bearing and big bearing 9" axles. 10" vs. 11". Everything from the housing ends (retainer bolt pattern), backing plates, shoes, hardware, drums. Really nothing from the small bearing housing brakes will work on the big bearing housing.

Now if you find a (70's big bearing) 9" housing from anything besides an early bronco the track width will be different and every mounting point will be wrong.
 
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1967Bronco

Jr. Member
Joined
Mar 7, 2012
Messages
65
What i have is a 9" big bearing rear end with 4:11's and a dana 44 with matching 4:11's. The big bearing is drum to drum and they both currently are in a 72 bronco. Currently i have the stock 1967 dana 30 and 9" rear end and was looking to swap out these two for the ones that are in the 72. I am just curious if its a simple bolt up or will i need some mods done to make it work?
 
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1967Bronco

Jr. Member
Joined
Mar 7, 2012
Messages
65
the basic question i have is.......can i take any rear from any 66-77 bronco whether its a big bearing or not and will it be a bolt on or mod fit
 

bknbronco

Bronco Guru
Joined
Jan 17, 2011
Messages
4,378
Loc.
North Metro, MN
Should be able to unbolt drive shaft and ubolts and bolt the new one right back in. There the same exact rearends, just the BB one has bigger brakes and bigger bearings.

Simple plug and play. Not sure what confused the other guys??
 

thegreatjustino

Contributor
Red Head Grease Monkey
Joined
Jan 23, 2002
Messages
15,620
Loc.
Stockton, CA
What i have is a 9" big bearing rear end with 4:11's and a dana 44 with matching 4:11's. The big bearing is drum to drum and they both currently are in a 72 bronco. Currently i have the stock 1967 dana 30 and 9" rear end and was looking to swap out these two for the ones that are in the 72. I am just curious if its a simple bolt up or will i need some mods done to make it work?

the basic question i have is.......can i take any rear from any 66-77 bronco whether its a big bearing or not and will it be a bolt on or mod fit


Sorry, I misread your post the first time around. Yes, you can swap any EB front or rear axle into any other EB. I am currently running a '77 rear end and a '74 front end in my '69 Bronco. Everything bolted up exactly the same as the original '69 axles.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
What i have is a 9" big bearing rear end with 4:11's and a dana 44 with matching 4:11's. The big bearing is drum to drum and they both currently are in a 72 bronco. Currently i have the stock 1967 dana 30 and 9" rear end and was looking to swap out these two for the ones that are in the 72. I am just curious if its a simple bolt up or will i need some mods done to make it work?

Yes, the rear is a direct swap. Any '67 to '77 rear axle is a direct swap. Just not the '66

Front axle goes right in as well. Use the '72 track bar, it has a bigger bend in it to clear the bigger dana 44 axle. Steering linkage is the same, use whatever is in better shape. The design of the ball and socket changed but they all interchange. Steering linkage didn't change dimensions until '76.
 

t120r

Sr. Member
Joined
Nov 25, 2008
Messages
629
So if putting a 1977 rear 9" into a 1966,one would have to change a shock mount to match. Seeing as there is welding involved, what would be the best course of action: changing the axle mount or the frame mount (to match later years) ???
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
Either way really. The newer style frame mount is easily purchased new, usually as part of the dual shock kits. The lower mounts are available as well.

Only the early '66 models had the unique rear shock mounting. Later in the same model year Ford changed to the style that continued through '77.
So of course check what you have before you decide. Easy to see the difference at a glance.

Paul
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
So if putting a 1977 rear 9" into a 1966,one would have to change a shock mount to match. Seeing as there is welding involved, what would be the best course of action: changing the axle mount or the frame mount (to match later years) ???

Axle mount for sure........Cut it off and weld it on where needed.......

Tim
 

t120r

Sr. Member
Joined
Nov 25, 2008
Messages
629
I was just curious as to the advantages, if any, of one style vs he other. If ride is the same, I'll just do the axle mount.
 

bknbronco

Bronco Guru
Joined
Jan 17, 2011
Messages
4,378
Loc.
North Metro, MN
I was just curious as to the advantages, if any, of one style vs he other. If ride is the same, I'll just do the axle mount.

Would be the same as long as you had the same shocks. The axle mount would be simple since you have the axle out and can weld it outside the vehicle. Frame mounts might get close to the body if you have no BL.

And since you have it out might as well drill and tap for a drain plug of some type. Shave and plateing that 9" is a worthy mod. Of course all new brake parts including cylinders and turning drums. Tapered outer axle bearings is a nice upgrade. I have a BB 9" that I picked up and stripped down and someday will swap it after I build it up.....for me that is everything above plus new spring pearches (to eliminate my 10deg shims) possibly with shock mounts on that instead of hanging off the axle. Also a re-gear (something higher than 4.10's), a selectable locker, and of course big boy axle shafts!
 

t120r

Sr. Member
Joined
Nov 25, 2008
Messages
629
A drain plug is definitely happening. No drums, I'm making brackets to mount discs on there. I've got the upgraded 31-spline Yukon axle shafts and it will be getting a tru-trac. Completely street driven machine.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
... and it will be getting a tru-trac. Completely street driven machine.

Why the limited-slip if it's going to live it's life on the street?
Not that there aren't some benefits of course, but depending on your driving habits, it might also be completely superfluous.
Relatively speaking.... ;D

Paul
 

t120r

Sr. Member
Joined
Nov 25, 2008
Messages
629
We get a lot of snow here and I use 4wd in my '92 ranger all the time. So I know I need that extra bit in the winter.
 
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