1973 Duster 8 3/4 rear end Lengths!?!?!

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73 Plymouth Duster

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Okay so I have a 1973 Duster that had a 7 1/4 rear end that measured 51.4 inches outside flange to outside flange. I found an A body 8 3/4 housing on craigslist then found an A body 8 3/4 3.55 posi center section and A-body 8 3/4 axles. I bought them both and put them together. (this was before I had a tape to measure the housing and took the guys word, stupid me I know) anyways tonight I measured the A body housing I bought and put together. turns out it is 53 1/2 in outside flange to outside flange or 53 1/4 center to center. which from that chart says it's a B-body early 60's rear end. Im beside myself right now. I measured the axles and I get roughly 27 and 7/8 or close enough to 27 and 11/16.

Just for grins and giggles i slid in the axle (with green bearings and backing plates) with no brake backing plates and right when the axle stud plate met the top of the studs i turned the rear end and it was grabbing. It was suspended in there from about 1 in out before i hit the bolt tops but I don't think I grabbed teeth? I dont know much about this rear end stuff.

SO is it expensive to have my housing cut down and rewelded? or should I buy new axles and bearings and have to long a rear end? any insight would greatly help.
 
Hey there-=;
I would be hesitant to start chopping up an axle housing, people do it but I would wait and get the correct stuff. "Consider The Following"...:shock:


  • Is this going to be a Street Car, Drag Car, Show Car?
    • If you intend to put some major power to the axles, consider some good aftermarket axles.
  • How soon do you NEED to get this part of the project completed?
    • Being patient and looking around could net you the correct axle housing and keep you from having fenderwell clearance issues. This will allow you to use stock wheels (If you like) and give you more wheel and tire options.
Ultimately I am a pureist and I would find the correct parts for the correct application. Oh, and 8-3/4 Third Members ("Pumpkin"...Center Section, ect) are not particular to A-Body, E-Body, B-Body, ect. You mentioned you purchased an "A-Body 3:55" gears.

Much luck to ya' and don't forget the dimensional changes that you may have to make to your driveline and the potential change in U-Joint and/or the mount attached to the pinion gear.

:eek:ccasion:
 
yes sorry I know pumpkins aren't body specific I jut miss typed. It's going to be a nice street car with some power.

So earlier I said I slid the axles in and they didnt grab well they just Barely do. If I were to slid it in on both sides it would only grab about 3/4 in. (which obviously isnt enough)
-CrackedBack. That is the reference point for dimensions that I am using now however it says like 63-72 a body 8 3/4 is 52 5/8 in. My car is a 73 idk what changed but something did because I pulled my 7 1/4 out and it measured 51.4in so logic would tell us the right rear end for my 73 car would be an 8 3/4 rear end that is 51.4 in. However everyone claims 52 5/8 and it works great but they probably used it on a 63-72 car like it says you should. MY AXLES are correct length at 27 11/16in

One more weird fact. THe wrong length rear end I now have is 53 1/4in and by what I can see it grabs the axles 3/4 of an inch in the center section. If these "correct" charts are indeed correct and it needs to be 52 5/8 that mean I need to shorten it a little more than 1/2 an inch. so then each axle would only grab an extra 1/4? So they would grab 1in total then? This is the logic I come up with based on the Correct rear end and axle lengths for an 8 /4 63-72 a-body rear end regardless of my car.

So what is the best route? shorten it to 52 5/8 in like EVERYONE says and put in the axles EVERYONE says ARE the right length and hope my "reckoning" is wrong? If that happens to work out and those axles do in fact work with a 52 5/8in rear end then GREAT! except I pulled a 7 1/4 rear end out of my car that measure 51.4 in.....HELP ME
 
The reason there are no references to 73 A body cars and 8.75's is because they never came with them. They went to the 8.25 rear in performance and HD applications. the spring perches and wheeltub width is the same from 67-76 on A body cars.

A body rear 8.75's are 52 5/8". Measure the overall, drum to drum width of the 7.25 rear you have. I bet it's REALLY close to 57 1/8" DO NOT make any conclusions regarding what an 8.75 requires based on flange width of your 7.25 rear, it's a recipe for disaster. And if you see that POS chart that says A body 8.75 rears are 51.40", burn it, it's WRONG!

The axles you have at 27 11/16 are too short for the 53.25" axle.. PERIOD! Don't bother to try. They are the right length for a stock A body rear.

You best make sure the flange ends are the same bolt pattern as your axle bearing plates.

If you are set on using the axles you have, the rear needs to be shortened. What's the bolt pattern of your axles?

Looks at that reference on Moparts I posted... IT'S RIGHT!!!
 
'73 and newer 5 x 4 1/2" bolt pattern A-body housings (7 1/4" and 8 1/4" C-clip design) are narrower than all A-body 8 3/4" housings.

A-body 8 3/4" housings are not usually shortened much narrower than 52 5/8" because the original housing ends collide with the U-bolts.

Stock A-body 8 3/4" housing 52 5/8" with 43" perches on center

Stock A-body 8 3/4" axles (5 x 4" bolt pattern) 27 11/16"

Aftermarket A-body 8 3/4" axles (5 x 4 1/2" bolt pattern conversion for common brakes) 28"

Stock '64-'74 8 3/4" axle end gap 1 1/2"

All measurements are taken square (not measured at an angle).
 
alright thanks guys. I decided that I will narrow my housing 3/8 of and inch on each side between the pumpkin and flange. that was I am at 43 1/4 perches (which is close enough for springs) and then ill be at 52 6/8 roughly. I may have them take off a smudge more than 3/8 to get closer to 52 and 5/8.

The housing I have is 53 1/2 end of flange to end of flange or 53 1/4 flange center to flange center. which one do I use. like how is the 52 5/8 measured? I am assuming it is end of flange to end of flange like the absolute total width and that's what I am basing my cuts off of 53 4/8 minus 6/8 (3/8 per side) leaves me with 52 6/8. Correct me if I am wrong.

And my old bolt pattern is 5 on 4.25 by my measuring. like center of one stud to center of the third one (like skip a stud in between) and I swear I have uni-lug cragers on them. My new axles are the exact same 4.25 However they don't have studs in them where do you buy them and how are they put in (are they pressed in?)
 
You measure to the outer surface where the backing plates bolt up, that's flange to flange.
 
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