I am planning to swap my pumpkin out when the weather permits on my 58. I would like to describe what I think I should do and would like to request any feedback from those who have performed this activitiy in the past to let me know if I following the proper process please.

1. Lift rear of car and place axle on jackstands.
2. Drain rearend fliud and remove rearwheels and disconnect drive shaft.
3. Remove nuts that hold each axle in place.
4. Using a puller of some sort "I will borrow one" pop each axle out and slide them out.
5. Remove all of the nuts around the pumpkin. Give it a couple of hits if required using a block of wood and hammer to break it loose.
6. Slide the pumpkin off and move it to the side.
7. Clean up surface where new gasket will mate with the new pumpkin.
8. Clean the gasket off of each axle and axle housing. "Do the rubber O rings need to be replaced on the axles ?"
9. Install the new gasket over the bolts and slide the new pumpkin in place and start putting the nuts on and tighen back and forth until all of the nuts are tightened.
10. Put the new axle gaskets in place and twist each axle until it inserts then install the nuts and tighten each axle.
11. Connect drive shaft, put wheels on and load up readend with new oil that is correct for a posi unit.
Drop the car and drive it.

If this all makes sense please let me know and if I missed something please let me know.

One other question please. With the posi pumpkin sitting on the bench should I be able to insert something into the space where the axle would go and turn it ?

Thanks very much in advance, John

 

first thought: are you going from an open rear end to a posi? i have a 56 rear axle housing and i had to shorten the driver's side axle approx 1/4" to make it fit when i went from open to posi..

that aside, the axles should pull out easily.. otherwise a length of chain attached to a couple of the studs and then 'jerked' should easily pull them out.

if the O-rings on the bearing are not flattened, then they could probably be reused; but i'd replace them if you can.

i would use an axle to check to see that it slides ALL the way inside on each side as there are 2 sets of splines on each side that the axle has to slide through.

don't forget the posi additive, do not rely on regular or synthetic lubes to work...
Bill

 

Thanks Bill...I am going from and open to a posi and I will check to make sure I catch both splines as you mentioned. I hope the length of the axle is not an issue.
I will look at the O rings carefully and if I am able to locate a set I will replace them regardless.
I will also take your advice and add posi additive.
Thanks again...

 

To pull the axles, after you have your brake drums off, re-install them backwards, loosely with all 5 nuts.

Then, use the brake drum as a "slide hammer" to pop the axles out.

Works every time. NO special tools needed.

That's an old "Indian trick".

Chuck

 

Shortening the axles, when going from open to posi, is ONLY an issue on 56 Vette axle housings/axles and 55-56 pass cars.
SOME PEOPLE have reported that it has ocassionally been and issue on 57s also, although, I've never experienced it on a 57 (Vette or Pass car).
Furthermore, NEITHER axle of a 56 should be shortened 1/4in. BOTH should ONLY be shortened about 1/8in!!!!!!!!!!!!!!!!!!
If the axle would not go all the way into the posi axle gear, it VERY POSSIBLY is because the splines of the 2 pieces of the axle gear are not lined up.
Below are four photos of an axle and the 2 pieces of the axle gear.
The first photo is the axle inserted all the way into the two pieces (56 axles get 1/8in cut off so that they don't protrude beyond the axle gear and cause interference with the center cross shafts of the posi unit, as seen in the second photo).
The third photo shows the 2 pieces of the axle gear seperated to show them individually.
The forth photo shows what happens when an axle is cut too short!!!!!!! It's not fully engaged into the inner part of the axle gear. NOT GOOD!








The 58-62 housings/axles were all the correct length for a posi, thus, ALL THAT NEEDS TO BE DONE TO STICK A POSI CENTER SECTION IN YOUR 58 IS TO POP THE AXLES, SWAP CENTER SECTIONS, AND PUT IT ALL BACK TOGETHER. EVERYTHING WILL FIT JUST FINE!!!!! Last, before sticking the posi into the housing, look into each side of the posi (where the axle splines are) with a flashlight to see if the splines are aligned on both pieces of the axle gear. Then stab an axle into each side to assure it goes all the way to the bottom.

Here is the center of a posi showing the cross shafts/spider gears. You can clearly see the shinny circle on the cross shaft where the end of an axle has been touching (because the axle was a little long).
And below that, is a broken cross shaft, caused by interference from an axle that was too long.

 

Just to be sure, switching from open to Posi will work just fine as well, right? I am planning to do a swap sometime in the next month or so.

DZ-- did you get your new PC yet???

thanks in advance!!

 

thanks Tom...
Bill

 

It arrived today. A dear friend, who is also my computer guru, picked it up a while ago to load up the programs that he pulled off of my old hard drive.
At the present time, I'm using my son's laptop.
I should be up to full speed with the new Dell tomorrow.

 

THANK YOU VERY MUCH I appreciate all of this information very much.

This is great detailed information and the pictures are very helpful. Also I like the old trick of reversing the brake drum, sound like that sill make thing a lot simpler.

DZ,
As always you provided some nice details. But with that it prompt me with another question I hope you do not mind. You mentioned that the splines should line up. What if they do not ? What would be the correction required ?
Again, thanks for the super pictures...
John

 

The fix is too easy, but it takes 2 people and BOTH axles.
Lay the center section on the floor.
Insert each axle into the axle gears.
Place some kind of heavy bar (such as a crowbar) between 2 lug bolts on each axle flange (place a lug nut on each bolt so that the threads don't get damaged).
Have a friend hold one bar while you rotate the other axle until the splines line up and the axle slides all the way in.

By the way, if you can rotate the axles in opposite directions by hand (on 60-64 posi units), the posi clutches are TOO loose.

 

We're up and running with the new DELL!!!!!!!!

 

What is it about the 56 that causes this phenomenon? Is it that the housing is 1/4 in narrower than other years? Or that the axles are 1/8 in longer than other years?

If you have a 56 in which the axles have been shortened, is it a problem to install an open pumpkin?

I ask because I have a 56 with a later posi pumpkin. I don't know the year of the axle housing. I don't know the status of the axles. I would like to change out the 4:56 final drive ratio.

 

no problem if the axle has been shortened. the reason for shortening the one axle is that it hits posi parts in the carrier that an open rearend doesn't have.

as to why the axle is longer, i don't have a clue... btw, 56 axle bearings are also different from later bearings...
Bill

 

OK, take a good look at the 2 photos below.
The top photo is an open differential, the lower one is the INSIDE (center) of a posi.
With an open differential, there is just the round shaft (for the spider gears) going through the center of the differential. In the posi differential, there are those 2 cross shafts which are square in the center. The splined end of 56 axles (55-56 for pass car) is just a little longer than 57-later axles. Thus, when you stick a posi rear into a 56 housing (55-56 for pass cars), the slight additional length (about 1/8in) of the 56 axles will make contact with those square cross shafts in the center of the posi.
The very outer ends (where the bearing fits) of 56 (55-6 for pass cars) axle housings has a smaller ID and the 56 axle bearings are smaller than 57-later bearings. Furthermore, the 56 (55-6 for pass cars) axles, where the bearing is pressed on, is TOTALLY different from 57-later axles. Consequently, you CANNOT interchange 55-56 axles/bearings/housings with 57-later. THEY WILL NOT INTERCHANGE!!!! Only the splined ends of the axles are the same which allows swapping of 56-62 (55-64 pass cars) rearend center sections.
As long as you have a NON-posi rear installed in ANY axle housing, there is ZERO issue with the axles (ANY YEAR)! But, when you install a posi rear into a 56 housing (55-56 for pass cars), it is necessary to cut off about 1/8in (3 /32 if you can be REAL accurate).
As I mentioned earlier, SOME PEOPLE have experienced axle interference with 57 axles, I have not seen this.

Unfortunately, I do not have any 56 axles at this time (I got rid of all of them, DUH). So, I cannot take a side by side comparrison picture of 56-57 axles at the bearing end to show you. You just have to take my word for it.

 

Thanks for the clarification. Is there a way to tell if I have a 56 (vs 57 or later) rear axle housing short of pulling out the axles and examining the bearings?

 

Yes----------------------Maybe.
The 56 (55-56 for pass cars) axle housings DO NOT have a drain plug on the bottom-center of the axle housing, they only have a fill plug. FROM THE FACTORY, only 57-61 housings got a drain plug (as well as a fill plug). No drain plug on a 62 housing (EXCEPT, maybe some VERY EARLY 62 housings). This also includes 62-64 pass car housings.
Now, if you have a 56 housing--------------------and someone has installed a drain plug on the bottom, then you have to pull an axle.
OK, so how do you tell what you have once you pop out an axle. The 57-later axles have a 3in diameter axle bearing. The 55-6 bearings are about 2 7/8in diameter.
You can also immediately tell by the width of the bearing retainer, but I don't have any to take a picture of to show you. The 55-6 bearing retainer is wide (almost 1in) and the 57-later bearing retainer is thin (about 1/4in). The bearing retainer is the stamped steel piece between the bearing and the wheel flange which has 4 bolt holes.

 

John,

I am putting a posi in my 61 in the next few days (car is on jack stands and posi is in the carrier). I have a couple of extra pumpkins.

I will try to take some pics for you and others. As always, Tom (DZauto) has given us all a great lesson even though I have done this a two times over the past 40 years.

Joe

 

here's a picture of the various bearings



Bill

 

Thanks Joe,

I look forward to seeing the pictures as you swap the pumpkin in your 61. I hope it all goes well...

I could not agree with you more regarding Tom (DZ) giving us a very useful lesson...

John