Rearend changeout

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gold swinger

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Hey fellow members. I have a 73 swinger and someone had changed out the rearend with an older small bolt pattern 7 1/4.I want to source an 8 1/4 and change it.What problems should I be prepared for? .The car would have came with a lbp 7 1/4 originally.
 
gold swinger said:
I want to source an 8 1/4 and change it.What problems should I be prepared for?
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You will need to obtain 8 1/4 or 8 3/4 shock plates and U-bolts, and another driveshaft or have your current one shortened.

gold swinger said:
The car would have came with a lbp 7 1/4 originally.
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I doubt that. I don't believe the LBP 7 1/4 came out until a few years later. In 73 you would get a 7 1/4 when you got drum front brakes and a 8 1/4 when you got disk front brakes. It would be more likely that someone upgraded your vehicle to front disk brakes, but didn't want to spend the additional money to upgrade the rear axle.
 
I currently have discs on the front.I believe it came that way.The car was originally slant 6 and change out to 318 four speed. I don't have any history on the car, but I imagine the original 7 1/4 blew up and sourced an older rearend to replace.
 
gold swinger said:
I currently have discs on the front.I believe it came that way.The car was originally slant 6 and change out to 318 four speed. I don't have any history on the car, but I imagine the original 7 1/4 blew up and sourced an older rearend to replace.
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My guess is someone swapped out the drum for disc, I believe a 73 /6 car would have had drum originally. My 74 came with a 318, front disc and a LBP 7 1/4.
 
I've done some research and 73 seems to be a mismatch year.Could be drums on front could be discs . Seems production date and plant seems to be the deciding factor. I highly doubt anybody updated to discs they only spent money on bare essentials.having said this I could be wrong.
 
gold swinger said:
I currently have discs on the front.I believe it came that way.The car was originally slant 6 and change out to 318 four speed. I don't have any history on the car, but I imagine the original 7 1/4 blew up and sourced an older rearend to replace.
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I'll attempt to clarify my last post. If your car came with a disk front, it got 8 1/4 axle. If your car came with drum front, it got SBP 7 1/4 axle. LBP 7 1/4 was not available at that time; I believe 76 was the first year for LBP 7 1/4.

No matter what it came with, you will need the parts I mentioned in my previous post to upgrade to 8 1/4. If you are already LBP disk brake front, but don't want the expense or need the added strength of 8 1/4, there are LBP A-body 7 1/4 axles available as well. You will have to swap the entire axle assembly though, not just the axle shafts. The good thing is you won't need spring plates, U-bots, or a driveshaft to swap in a LBP 7 1/4.
 
Brad4406 said:
I'll attempt to clarify my last post. If your car came with a disk front, it got 8 1/4 axle. If your car came with drum front, it got SBP 7 1/4 axle. LBP 7 1/4 was not available at that time; I believe 76 was the first year for LBP 7 1/4.
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74--my 74 Dart Sport had the 7 1/4 LBP in it.
 
Brad4406 said:
Thank you for the correction. :)
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Lol, but.....if it had been a /6 car with drum front it may have had the SBP. It's odd when changes were made in production cars, it was like a box of chocolates, you never knew what you were gonna get.
 
I would like to clear some of this up for you.
After owning several and personally seeing hundreds of a bodies from '73 to '76, ALL power brakes equipped cars got the BBP front discs and BBP rear end, regardless of the engine ordered.
With slant 6 cars, it was usually the BBP 7 1/4 rear, but it is possible that a 8 1/4 rear could be factory installed,
With 318 cars, power or manual brakes, you automatically got the BBP discs up front and usually a BBP 7 1/4 rear, but i have seen quite a lot of them with 8 1/4 rears too. ( About half and half).
With 340 and 360 cars, they all came with power disc brakes in BBP and a BBP 8 1/4 rear axle.
ALL cars built after January 1st 1976 regardless of engine got BBP front disc brakes and a BBP rear.
ALL slant 6 cars without power brakes got the SBP drum brakes and 7 1/4 rear up until January 1st 1976 by default, as there were no 8 1/4 rear axles produced with SBP.
I hope this helps you and some others..........
 
In Canada, 74ups all As got discs, and the LBP. Supposedly, the slantys also got discs as standard. I have never seen a 74up a with sbp.
In Canada the 73 V8s got DBs and LBP, while the slantys usually got drums and sbp. This is not written in stone.
All the Canadian73 Scamps and Darts,with slantys, that I have come across, had sbp. I assume they were drums.
Having said that, I confess, I have not seen hundreds of these cars. Perhaps a few dozen.
 
AJ/FormS said:
In Canada, 74ups all As got discs, and the LBP. Supposedly, the slantys also got discs as standard. I have never seen a 74up a with sbp.
In Canada the 73 V8s got DBs and LBP, while the slantys usually got drums and sbp. This is not written in stone.
All the Canadian73 Scamps and Darts,with slantys, that I have come across, had sbp. I assume they were drums.
Having said that, I confess, I have not seen hundreds of these cars. Perhaps a few dozen.
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Please re-read post #11.
I have personally looked at hundreds of these cars in both the U.S. and Canada, and that's where i draw my conclusions from.
I have a '75 Dart Sport slant 6 with standard drum brakes from the factory, it's one of my donor cars in my build thread. (The red one).
I have a '74 Hang 10 Dart Sport slant 6 with power brakes and BBP discs and a BBP 7 1/4 rear end.
I either own or have owned or seen other cars from junk yards to car shows over a lot of years to back up my research..........
 
Seems like a box of chocolates lol.Mine is a Canadian car but there seems to be a mismatch of whatever was on the shelf.So correct me if I'm wrong but I need 3 inch u bolts and shock plates and a shorter driveshaft.If I could source a driveshaft and rearend from a dart should go pretty smooth emphasize on the smooth.thanks for the info
 
Yeah, I saw that post, and realized, mine sorta conflicted with that, so I added the qualifier, that I really hadn't seen that many. Especially slantys; I just don't pay much attention to those.
 
gold swinger said:
So correct me if I'm wrong but I need 3 inch u bolts and shock plates and a shorter driveshaft.If I could source a driveshaft and rearend from a dart should go pretty smooth emphasize on the smooth.thanks for the info
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Pretty much.
 
AJ/FormS said:
OP,
You know a teener will have a tough time killing a SG 7.25, right? And you already have the D/S. And lbp 7.25s are cheap. Almost come and get it outta my shed,free cheap.
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^^ This sounds like good advice. But if you go ahead with the 8.25, you might be able to use the shock plates and drive shaft from the same donor car. If it's a Dart or a 4-door Valiant, it should have the same 111" wheel base as your Swinger (Duster/Scamp are 108"), and so the driveshaft might fit without cutting.
 
So basically as aj said.This is just a cruiser that I enjoy totally. If I upgrade to lbp 71/4 eliminate the wheel adapters on the back ,and I'm down the road with little grief.I'm slowly eliminating troubles.I'm putting new leafs ,hangers and new shackles brackets etc at the same time.First car I owned was a 75 swinger and at 50 just bringing back some fun.this is an awesome form and appreciate your help.
 
Recent-ish owner of a 73 Swinger as well and have gotten to do most of what you are looking to do.

Found an 8 1/4 with the larger bolt pattern from a 76 duster that had shock plates. Rebuilt it - threw in a 3.55 trak-lok carrier out of a Dakota I found on eBay because it had the highway open carrier 2.76.

When it came time to take out the 7 1/4 we just cut the old u-bolts because they were indeed rusted/caked and you have to change them out to larger radius anyway.

Right before winter hit I ordered and installed a set of Mancini heavy duty leaf springs and original style shackles. Can not be more pleased with the way the car sits (and corners!) now. Only thing that took a little while was the new front-spring eye bolt was heavier duty and had to open up the bolt hole a bit. Still only took an afternoon to change out. The picture shown is right before the leaf spring install with the horrible chevy-style shackles I was trying to get by with. Most likely get plenty of other recommendations on springs from others on here but I'm glad I went with the Mancini and not priced badly at $235 for the pair. Correct left and right with the passenger side with a bit more arch to it can be found here Mancini Racing Heavy Duty Leaf. Broke my camera but will try to get some photos if you are interested in now it sits on them.

As for problems, others stated what I ran into - Shortening and balance of the driveshaft (I was charged $75 at a local shop). The duster rear end had the same pinion yoke size so didn't have to change that.

Looking forward to spring and hope your swap out goes well too!
 

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