Hey folks, I'm building a hotrod 1950 Plymouth P-19. It has an 111 inch wheelbase and is close to the same weight, length, and width as an A-body. A lot higher, though.

I also have a '74 Valiant that I'm going to take the /6 from. I'm planning on just a mild build with maybe an RV cam, Super Six, Dutra Duals. Electronic ignition already there.

Transmission is a 904.

I'm not sure yet what the 7.25 ratio is. I would want at least a 3:23. Do 7.25s come in 3:55 rears?

So----would keeping the 7.25 be a waste of time? What would you all recommend?


Thanks,

Joe

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Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"

Sounds to me like a 7¼" rear axle would be a perfectly fine choice for that vehicle.

7¼" rear axles were available over the years in a large range of ratios. 2.29, 2.45, 2.76 (very common), 2.93, 3.23, 3.55, 3.91.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The 7 1/4 rear should be fine. However, if you want a limited slip rear, an 8 inch Ford might be a better choice. 7 1/4 sure grip units are not very common, and not available new. The 8 inch Ford from an Early Mustang, Falcon, Comet, Granada, etc. is the same width and spring perch dimension as the "A" body 7 1/4. It is somewhat stronger, has the 4 1/2 bolt pattern. Gears and limited slip units are available new, if unable to find used. These rears are in salvage yards for about $100, drum to drum. It also has a drop out center section.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

7.25 is fine, but pretty weak if it has too much wear, one hard
jump on one that is worn and it's gone......

Check your spider gears in the carrier, if sloppy replace them,
there kind of the weak point.

Randy's Ring and Pinion, as well as others, still have pretty
good selection of gear sets from 3.23, 3.55 down and the
prices are not too bad (around $300 for spiders and R&P
together, not installed, open set).

The later 7.25 axles also have a adjustable carrier lash (somewere
after 69?)
and I do not like it as well as the shimed type carrier early axles.

If it were me and I had a choice, go with a heavier axle and carrier.

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http://imageevent.com/jeffc
62 D100 225 3sp lwb
64 D100 A318 727pb custom lwb
66 D100 A318 4sp lwb
68 D100 B383 727 swb
65 Belveder A318 727 4d
65 Dart GT LA273 2bbl 904
73 Scamp 225 2bbl 4spOD
Old iron or no iron

Ratios are available up to 4.11. Randy's Ring and Pinion is one source and Jaws Gear is another. Jaws ( Moser ) is a little lower cost, Randy's has a wider selection of manufacturers to choose from.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Being a DeSoto guy (51 Sportsman hardtop with LA v8 , B car front suspension , Lincoln 9" rear w/disc) I wonder why you dont just keep the Plymouth rear. They are usually a removable carrier and have pretty good brakes. The 7.25 is not a drop in fit.

The good part about the 7.25 is that it will solve some E brake problems.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Probably going to be too narrow.

I put an 8 3/4 out of an A100 Van in my '48 Plymouth, and it fit great. I know the sheet metal is pretty different, but I think they are very similar under the skin, '50 Plymouth vs. the '48 Plymouth.

I will look, but I think the A-Body rearend is much narrower than the A100. Number I remember for the van rear is 61", flange to flange.

[Edit] Moparts shows 57 1/8" for the A-Body and 61 3/4" for the A100, drum to drum.

You could make it work with deep wheels, but then you’re stuck buying, or modding, a set just to get it to roll.

My setup fit 235/60-15 on a set of stock 15x7 wheels, and I don't remember there being much room next to the spring. Offset should be around 4". A six inch rim would need something like a 1 1/2" offset to fit an A-Body rear under there.

I could be wrong though.

Hey, you wouldn't be looking for a disk brake kit for that car, would you?

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Biggest problem I see is you need a drum puller to do anything to the rearend.

Probably not the right name, what I mean is that the drum is a pressed on piece and requires some kind of a tool to get at anything, including dropping the center section. Kind of a hassle, unless things never go wrong.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

My linclon rear is 63 "wide and with 15x7 cop car rims its a lil tight on the outside of the fenders with 235 /78 / 15 wide whites. Clearance on the stock springs is close.

Your Plymouth would be identical to my DeSoto.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Thanks for all the replies.

Nice looking ride you've got there, Sandy. My concern with the rear end is mainly about the brakes, e-brakes all of that stuff.

From the numbers I've looked at (unfortunately don't have them here at the moment) the A-body rear is about 1" too wide, not too narrow. Somewhere around 56-55" for my Plymouth.

Yes I am interested in disc brakes for the front.

I have a 74 Valiant w/ disc brakes up front that could go for barter/sale, etc.

Joe

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Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"

Find an 8-1/4 from a Dakota or Cherokee. I dont remember which one but one of them is 54" inside of backing plate to inside of backing plate.
I remember measuring them both up when I was looking for an alternative rear for my Volare before I found one that came from another F body. Seems it was the Cherokee IIRC. Also Dakotas '91 up went to a 6 lug flange so find one from 87-90.

Sandy, that hardtop DeSoto is a good looking car.

There are several sources of disk brakes for you to consider, most use parts you can get from NAPA or Autozone.

Having to pull the axles is a hassle, JC Whitney used to have a good price on the drum puller. I don't see much work with maintaining the brakes. I have a '47 DeSoto, I think I will leave it stock.

A 7.25 would be ok for the use of your ride, a decent rear for a non performance application and they can be had cheap or better yet free!
I run a 7.25 sure-grip rear in my street/strip car but however 7.25 suregrips are difficult to find. Ive made several passes with mine and it's tough as nails! Ive ran slicks on this thing and it hasnt even offered to break and it's lighter than the 8.25 and 8.75 rears. I guess if I ever break this rear I'll go to an 8.25 which is more than enough to handle all but the most of extreme of slants. Cheaper to get a suregrip for an 8.25 than the 8.75 as well. I find the 8.75's are way to expensive to fool with.

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Barret-Jackson: Ruining the car hobby for everyone!