differential compatibility

[matthon]

Read the entire thing.

I know the difference between tapered up to 64, and flange 65 and up.

Isn't the conclusion of this thread that 62-63 open centers cannot be swapped into 64 and up?

The link above states:

2) Any 8-3/4" center section may be interchanged for another as an entire assembly.

 

[matthon]

According to this, the thrust block was thicker in open differentials up to 63:

Guide to the Chrysler 8-3/4″ rear axle

Please note that this page was copied in its entirety from AUTO HOBBY DIGEST The writers of this page really did some digging to be this thorough, and they deserve all the credit in the world for i…

www.mopar.nl

The opposite of this thread.
I tend to believe fbbo members over websites.
This is getting confusing for my tiny brain.

Even the link I just posted states you can't swap a 64 up differential into an earler open rear without machining the axles or using the earlier Sure-Grip axles.

If the thrust block was thicker in early open ones, wouldn't that make those axles shorter?
So why would swapping in a 64 differential require the axles to be machined? Machined what, longer?

Doesn't matter anyway, because I want to do the opposite, put a 62 open center into a 64 rear.
Can you do that by removing the thicker thrust block and dropping a skinny one in there?

Sunday night brain gymnastics hurt my head.

 

[khryslerkid]

@matthon
We'll just talk '62 '63. The open 8 3/4 used a longer (taypered) axle. The sure grip used a shorter axle, only about a 1/4" or less, closer to a 1/8". So if you swapped in a sure grip and originally had a open diff you would need the shorter axle or have your original axles shortened.

The open diff used a square block for the axles to butt against for adjustment. The sure grip used a square block with the "buttons" to butt against for adjustment. That's why the need for the shorter axle.

Probably just to make things simpler, in 1964 my guess was they changed the diameter of the block in the open diff or used the solid block with buttons so the same length axles could be used for either diff. The '62 open diff used a piece of square tubing. (Anyone have a '64 open diff to confirm?) Then in 1965 they went to the flanged axles with the external adjustment on one axle instead of the taypered axle with shims.

 

[matthon]

We'll just talk '62 '63.

To continue with this, if one were to swap a 62 from a Sure-Grip to a 62 open diff, do you need longer axles?
In this scenario, you would start with the shorter by 1/8 axles, do you need to make up that 1/8 or can the shorter axles live happily inside an open diff?

Or, can you just throw in a square block with the "buttons" into the 62 open diff?

Most I imagine are swapping open diff to Sure-Grip, so they would need shorter axles, or have them machined down.

I want to go Sure-Grip to open diff, so my axles are too short.

 

[33 IMP]

To continue with this, if one were to swap a 62 from a Sure-Grip to a 62 open diff, do you need longer axles?
In this scenario, you would start with the shorter by 1/8 axles, do you need to make up that 1/8 or can the shorter axles live happily inside an open diff?

Or, can you just throw in a square block with the "buttons" into the 62 open diff?

Most I imagine are swapping open diff to Sure-Grip, so they would need shorter axles, or have them machined down.

I want to go Sure-Grip to open diff, so my axles are too short.

Tack weld a flat washer on em (grade eight, hardened one)

 

[matthon]

Tack weld a flat washer on em (grade eight, hardened one)

That actually sounds so simple I don't see why it wouldn't work.

 

[khryslerkid]

To continue with this, if one were to swap a 62 from a Sure-Grip to a 62 open diff, do you need longer axles?
In this scenario, you would start with the shorter by 1/8 axles, do you need to make up that 1/8 or can the shorter axles live happily inside an open diff?

Yes you would need the longer axles. Maybe the 1/8" washer would work. I guess that would require removing the spider gear pin to remove the block for easy access for welding.

The thrust block is used to butt the axles up against for proper end play. Only way to not use the thrust block is to use Green bearings.

Looking up replacement buttons on Dr Diffs site it's stated not for any cone or open differentials. So apparently there's no open diffs that used "buttons". I emailed Cass and asked him what was changed in '64 that both open and Sure-Grip used the same length axles. Waiting to hear back.

 

[33 IMP]

I guess I wasn't clear. Tack the washer to the end of the axles., not the block.

 

[matthon]

I guess that would require removing the spider gear pin to remove the block for easy access for welding.

I took it as weld a washer to the end of each axle.

 

[khryslerkid]

I took it as weld a washer to the end of each axle.

Oh, I guess that would be easier

 

[matthon]

I guess we'll find out, as soon as my springs get here.

Let me know what Cass has to say.

Wagon getting the later rear from the 2 door slant 6 car, as well as the big meats.
Keeping the 2:76 Sure-Grip from the wagon.

 

[khryslerkid]

Let me know what Cass has to say.

Cass returned my email last night. I asked him what changed in '64 to allow the same length axles to be used for both open diffs and Sure-Grip diffs.

"In 1964 Chrysler installed a round, 1.5" long thrust block in open differentials to match the length of the thrust buttons in the sure-grip."

 

[matthon]

"In 1964 Chrysler installed a round, 1.5" long thrust block in open differentials to match the length of the thrust buttons in the sure-grip."

Looks like the options are:
Weld 1/8 thick washers to the ends of the axles.
Get/install a round 1.5" long thrust block.

I guess that leads to a few questions:
Can one get said thrust block?
Will the 62 open diff accept the 1.5 block?

Need to do a search to see if any thrust blocks are available used, Mopar sites, ebay.
As well as drag out my 62 center and take a look just to see what this thrust block looks like in person.

 

[khryslerkid]

Looks like the options are:
Weld 1/8 thick washers to the ends of the axles.
Get/install a round 1.5" long thrust block.

I guess that leads to a few questions:
Can one get said thrust block?
Will the 62 open diff accept the 1.5 block?

Need to do a search to see if any thrust blocks are available used, Mopar sites, ebay.
As well as drag out my 62 center and take a look just to see what this thrust block looks like in person.

Most people go the opposite direction, open rear to a limited slip. You have to be different

But it brings up some questions and facts that most don't know about. I never would have thought installing an '63 or older diff into a '64 or newer housing would be a problem. But now we know there's a difference.

The thrust block in my '62 open diff looks like a piece of square tubing that the axles butt against. I'm not sure of the measurement. I'd probably lean towards the washer on the end of the axle and if it's too tight/long you can always grind a little bit off. Using shims is the way the taypered axles were adjusted so it shouldn't be too hard. I'll say good luck for now

 

[matthon]

The thrust block is used to butt the axles up against for proper end play.

I don't think I understand this.
Is the goal to keep the axles from sliding in and out of the housing?

Iirc, the axles out of my 62 rear had tapered bearings behind the hub, seems like the axle cannot go in any farther.

 

[khryslerkid]

I don't think I understand this.
Is the goal to keep the axles from sliding in and out of the housing?

Iirc, the axles out of my 62 rear had tapered bearings behind the hub, seems like the axle cannot go in any farther.

Like most taypered roller bearings there needs to be some preload. On these early taypered axle housings the one side is fixed with the bearing retainer. The other side uses shims under the bearing retainer to apply the correct amount of end play. The thrust block makes the connection between the two axles to obtain the correct measurement/preload on both bearings. The newer (1965 up) housings use a threaded adjuster on one side to set the preload.

It's all explained in the Factory Service Manual. Let me know if you don't have one.

 

[matthon]

2070741 case.
What's the gear ratio?
It's 2.93, right?

 

[33 IMP]

Yep.

 

[khryslerkid]

Looks like it's stamped 1964 also

 

[matthon]

Looks like it's stamped 1964 also

I was going to ask how to tell if it is 64 and newer.
Guy said he has had it for a long time, thought it came from a 66.