Rear drum tight... Wrong brakes or axles?

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69fstbkcuda

69fstbkcuda

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Just swaped an 8 1/4 to 8 3/4.
Bought the housing and axles separate. Anybody know why the drums bottom out before they seat on the axle? It's causing them to lock up.

(Pic reference) Where the red arrows are there is about a 1/8" - 1/4" gab between the axle and drum. They are bottoming out where the backing plate an drum groove are. (Green)

image.jpeg
 
That does not look right. There should be no gap on hub. IIRC the 8.25 had a larger register than the 8.75 and they dont cross over.
 
pishta said:
That does not look right. There should be no gap on hub. IIRC the 8.25 had a larger register than the 8.75 and they dont cross over.
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8.25's use the exact same 10x2.5" brakes as the BBP 8 3/4's.

As for the OP, you've got mismatched parts. If the drums hit the backing plates you've got the wrong backing plates, drums, or axles somehow. Is this an A-body 8 3/4 housing? Are the axles original? What bolt pattern is on them, and have they been re-drilled? The wheel studs look like they're swimming in some of those holes in the drums. Something's wrong. What size are the wheel studs?
 
72bluNblu said:
8.25's use the exact same 10x2.5" brakes as the BBP 8 3/4's.

As for the OP, you've got mismatched parts. If the drums hit the backing plates you've got the wrong backing plates, drums, or axles somehow. Is this an A-body 8 3/4 housing? Are the axles original? What bolt pattern is on them, and have they been re-drilled? The wheel studs look like they're swimming in some of those holes in the drums. Something's wrong. What size are the wheel studs?
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Bought the housing off craigslist. It's supposed to be and A body housing. It fit like a glove when I put in. I'm assuming it is the correct width. It came with springs, brakes, and axles. No third member. It was all apart and needed some tlc. The axles are big bolt pattern. I'm using the same wheels and lug nuts from my 8 1/4. The backing plates and drums measure the same. Where I'm getting a different measurement is on how far the axle sets off from the backing plate. The 8 1/4 sets 3 1/8" out and the 8 3/4 sets 2 3/4"

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Those are NOT BBP axles, those are redrilled SBP axles. You can see the weld marks where they welded up the old holes for the studs. And look how close the studs on the 8 3/4 axles are to the edge of the flange. You're using BBP brakes with re-drilled SBP axles.

Arrows to where the old holes were welded up and ground down. If you want to use those axles, you'll have to find a SBP set of brakes and re-drill the drums. Personally, I'd buy new axles and use the brakes you have.
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Actual factory BBP axle. You can see the center register is a larger diameter and more raised, just like the 8.25" axle flange pictured above. Diameter of the flange is about 5-15/16", the picture with the tape measure isn't a good likeness because the camera is too close, too much angle from the lens to the object to read the tape correctly. But even in that picture you can see it's a much larger diameter than the SBP axle flange. And you can see how much more flange there is between the studs and the outer edge.

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IMG_4291.JPG
 
haha just bought all new housing studs/nuts and axle studs/nuts off @DoctorDiff. Wishing I would have bought a complete rear end off from him now. I was trying to save money by buying everything separate... gonna end up having more money in it and its just a 741 open 3.55 :BangHead::soapbox:


thanks for all the help!
 
I run 3.55s. They are a great street compromise gear. And on the street you will probably never have trouble with the 741 carrier. Just make sure the pinion nut stays tight!
And you do have a SureGrip in it right? And the center spacer better still be in there,lol. On the cone types, it's captured by the crosspin so don't sweat it if you have that.
 
AJ/FormS said:
I run 3.55s. They are a great street compromise gear. And on the street you will probably never have trouble with the 741 carrier. Just make sure the pinion nut stays tight!
And you do have a SureGrip in it right? And the center spacer better still be in there,lol. On the cone types, it's captured by the crosspin so don't sweat it if you have that.
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Oh boy! Don't know if it's a sure grip or if it will even roll down the road lol... I've had the car since I was 12 my dad bought it for me out of a junk yard. I worked on it from then until I was a junior in highschool before I got it running. It had a super 225 small bolt pattern, drum brakes all around 7 1/4 rear. We converted to disk in the front BBP drum in back with an 8 1/4 243 gear out of a 73 scamp I believe. Pulled the 318/904 from my uncles satellite. I drove it for a couple of years and fried the wires. Got married had kids and it has set in the garage since. I'm 31 now and have forgot everything about mopars lol. Pretty sad I knew more when I was a kid then now.

Anyways my kids keep asking me to get it going so I got excited and started ordering a bunch of parts for it without researching what I really want and need... And here I am posting threads like a ***** and relearning everything. I really do appreciate all the help I get from here. I don't have anyone else to help me get her back on the road.
 
I'm running an open 3.55 chunk that I pulled out of the junkyard in my Duster right now. Not that bad at all. Still can manage decent speeds on the freeway, not too bad around town either.
 
Just to be clear I need to remeasure my housing (supposed to be an A body) and order big bolt A body axles right? Not BBP B body. Stupid question I know... Just tired of buying the wrong stuff lol
 
69fstbkcuda said:
Just to be clear I need to remeasure my housing (supposed to be an A body) and order big bolt A body axles right? Not BBP B body. Stupid question I know... Just tired of buying the wrong stuff lol
Click to expand...

Yes. BBP A-body axles. Based on your description of the installation, and the fact that you have re-drilled SBP axles I'm pretty confident you have an A-body 8 3/4. A-bodies were the only ones that got the 5x4" pattern. But just to be sure get yourself a backing plate to backing plate measurement. Then call Cass @DoctorDiff so you can tell him what you've got, just to be sure (vs just placing an online order). He'll know what you need and the right questions to ask before he sends something out. He will ask, but sure you tell him you want the axles to work with the 10x2.5" BBP brakes you got from your 8.25.
 
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