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What is the deal with this Rear End Housing?

M

Meangene83

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So I have been reading and reading. And it has been hard to grasp exactly what it is my car has and what it is I can do with it.

I own a 1973 Plymouth Road Runner. And to my knowledge this is the original rear axle.

I have seen the graphic that shows the Rear End housings from the rear view and identifies them...

From that graphic it looks as though I have an 8 3/4 housing?

Currently the car has the One Wheel Peel.

Am I able to swap out the Gears inside the housing and make this a Posi Rear End which leaving the axle in the car?

OR

Do I need a whole new Posi Rear End Axle setup?

IMG_1812.jpgIMG_1814.jpgIMG_1815.jpg
View attachment 230623
 
you need gears of your choice and a posi unit
 
Yep that's an 8 3/4, what you need is a sure grip carrier (it's what the actual gears are bolted to). You can use the same gears and housing and everything you have, but it's easier to buy the center section w/ the sure grip already in it
 
first , it is an 8 3/4
second , posi is a chevy term , we mopar people and Chrysler call them by their true term "sure-grip"
yes there are clutch type and cone type "sure grip" units that are bolt in. there are many gear sets to choose from. there are also different "cases" to choose from depending on what you are using the car for.
 
Sure Grip. Got it.

Ok Clutch Type and Cone Type. So I choose from those two types.
Cases are the actual Housing for the gears themselves?

I am basically tooling around town and stomping on the gas at redlights.

Thank you
 
Yep, the case is the housing for the gears themselves, for just tooling around town and stomping on the gas at stoplights any of them will be fine

in your first picture, on the other side you'll see some numbers, last 3 digits will tell you what case you have

97950-500-0.jpg


This one's a 741
 
Easy swap find a sure grip pumpkin pull out old one replace with new one ! Lol well not quite that easy but its not bad at all !!:headbang:
 
When you guys use the Pumpkin term? What is that related to? A specific type or a general term for a rear end housing?

Also this guy seems to have a ton of crap.
http://boston.craigslist.org/gbs/pts/4808514815.html

Anything there stand out as possibly useful?
I guess it would be a smart move to read my Case's numbers, and like someone mentioned. Find the same Case But a Suregrip version?

If I don't find the same case, but it is a sure grip? Does that cause a whole cluster f of changes that need to happen?
 
the picture I posted of the 741 carrier? That's a pumpkin - the part of the 8 3/4 rear end that unbolts and comes out the front.

If you find another case that is a sure grip, but it's not the same case number? No problem! just swap out the existing center section for the sure grip one. Pull both axles, the drive shaft, 10 bolts and you're in.
 
Worse case you may have to change the rear universal joint to match the new pinion yoke.
 
Hey thank you very much for taking the time to answer these questions.

I am an expert in my field of employment, its tough being on the opposite end and asking all the dumb questions! :)

Now that i have a rough idea of what to do, I will feel confident looking at parts as I search the wonderful world of craigslist.
 
No such thing as a dumb question.

Just an observation...on your rear axle...seen fairly good cases of corrosion, but...
Almost looks like right out of the swamp. But, who knows, a little sand-blasting here and there.

8 3/4" rears are plenty. Just have to look. Easy to find another in much better shape...maybe even with gears and such like you want.

Sorry, not trying to be a wiseguy, just making a dumb comment.
 
Your local Craigslist guy has two center sections. Call him and find out what gear ratio they are and if they are Sure Grip. I would suggest 3.23 gears at least, 3.55 is good, 3.91 is about as high as you might want to go on the street.
 
Thanks Miller, I appreciate the observation. It is pretty dirty and in rough shape.
If mechanically it works, then I will keep it this season. Swap it out next year after I finish off paying for the rebuild.

The goals this off season are, engine rebuild, possible 4 speed conversion and Sure Grip rear end conversion.

After that and depending on the state of the piggy bank, my mechanic will be doing the leaf springs, adding coil overs.


Gregs, thank you for explaining the gear ratios. That makes sense.
Just as an aside, is my understanding correct? That the Higher the number, (higher the ratio) the easier it is for the car to turn the gear and as a result moves faster? Making the car faster?
 
not really..

the higher the number = the lower the gear ratio..

For instance, 3.55 to 1 indicates that the input (engine) rotates 3.55 revolutions to the output's 1 revolution.

A low gear (high number) gives more power to the rear wheels, along with faster acceleration, but the engine runs out of revs at the high end.. so it's a tradeoff (for example, in my car I had 3.23's, and I could cruise no problem anywhere at a comfortable rpm.. I put 4.10's in, and now I come off of the stop lights like a rocket, but if I go down the highway I'm running over 3000 rpm's to keep up w/ traffic.. this would be no problem if I lived in town or didn't drive my car long distances)

The engine speed maximum RPMs and the transmission ratios, final drive ratio, and tire size determine the car's rpm in any given speed, so there's some things you can do to effect it, but we'll get into that in another post ;)
 
Looks good. You can swap this out in your garage. When you get your old gears out you can find the gear ratio stamped on the ring gear. You can then use a chart to find out which speedometer drive gear you might need to put in your transmission so your speedometer reads correctly.
 
Went this morning. Took a look, the guy cleaned it up and thru some oil in it and it rotated nicely. All the gears looked in good shape and it had the 3.23 stampings.
Paid $450 and on my way.

Thanks to everyone for the help.
 
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