11" drum scraping backing plate after conversion; axle sits deeper after diff swap. What's up?

[khryslerkid]

I'm 99.9% positive the 741-case 2.76:1 unit I pulled out is original to the '68 Satellite, so it stands to reason the round thrust block is the correct one for that era. From what I could tell, it had never been removed until I pulled it.

Might look into some of the '50s Mopar forums to see if I can dig up any more info on these square blocks.

-Kurt

Hey Kurt, I have the same thrust block in my 1962, 741 open diff that I just pulled and replaced with a suregrip.

I guarantee it's just a piece of square tubing. I can even see a burr on the end of it from a saw blade. Thinking about it, it's all that's needed on a open rear to butt the axles up to, to set the bearing play. Can you see a date stamped on the ring gear like mine? (11-15-61)

 

[khryslerkid]

You're probably going to find that that 742 diff is going to require a longer axle. In 62 they used a 1/8" longer axle for the open rear verses the sure grip. Just an example, but it shows how they changed things just enough to make the swap difficult without having the right parts. Or maybe your 742 came out of a housing that required a different length axle.

 

[cudak888]

Hey Kurt, I have the same thrust block in my 1962, 741 open diff that I just pulled and replaced with a suregrip.

I guarantee it's just a piece of square tubing. I can even see a burr on the end of it from a saw blade. Thinking about it, it's all that's needed on a open rear to butt the axles up to, to set the bearing play. Can you see a date stamped on the ring gear like mine? (11-15-61)

Well, that answers that. I'll check the ring gear later tonight.

-Kurt

 

[cudak888]

First, I've found the source of the misinformation that led me to put less thought into the thrust block than I should have before doing this swap:

From: http://www.mymopar.com/Mopar8_75RearEndGuide.htm

There was a difference in thrust blocks prior to 1964 that make center section interchange, as well as axle interchange problematic. The thrust block, or "axle shaft thrust spacer", it thr block that both left and right axles butt up against inside the center of the differential. Prior to 1964, all open differentials used a thrust block was approximately 1/8" to 1/4" thicker than units made after 1964. The Sure Grip thrust block prior to 1964, however, was indentical to all 1964 and later Sure Grips and open differentials. In 1964, the thrust block width was changed to match the Sure Grip thrust block width.
​

That paragraph should read "Prior to 1964, all open differentials used a thrust block was approximately 1/8" to 1/4" NARROWER than units made after 1964."

Either way, I got screwed. Fancy that; seems to be par for the course working on a Mopar. That said, my diff is from March 4th, 1964:

 

[Cranky]

Misinformation from a web site applies to all brands but with me, Mopar has always been an easy brand for me to work on. Chevy on the other hand has always been problematic. Seems like when it comes to GM, I have 10 black thumbs. Ford...that's another story all together. Biggest problem with them is they like to make midyear changes and not tell anyone....

 

[khryslerkid]

I'm wondering if you can change the block to the newer one. Only other option is Green bearings.

 

[cudak888]

I'm wondering if you can change the block to the newer one. Only other option is Green bearings.

Pretty sure it can be swapped - if I could find a replacement block.

Rather keen on some really nicely kept Kelsey-Hayes rims for sale locally though, so will probably try to sell this off so I can get those.

-Kurt

 

[mopar 3 B]

Just change the spacer from one diff to the other.
I do not remember having to remove the ring gear on the 8 3/4 to take the pin out.

 

[cudak888]

Just change the spacer from one diff to the other.
I do not remember having to remove the ring gear on the 8 3/4 to take the pin out.

Easy enough, if I hadn't put the 2.76:1 back in the car the same day. Much more keen on enjoying the car than constantly having it up or down for some such disaster - I hadn't driven it since May due entirely to the dash cluster issue that I had to sort over a few months worth of weekends. And given what I use it for, I still think an A999 in place of the 904 would be a better choice for the engine's powerband.

That said, there's another reason for thinking A999: That's the one part of the car I've done nothing to (short of filter and pan), and - to date - everything that I haven't serviced has been trash; including, but not limited to: Upper control arms, lower control arms, shocks, exhaust, cylinder heads, main and rod bearings, dash wiring, instrument cluster, upper front seat back, all steering parts with ball joints, driveshaft universal joints, weatherstripping (not there) and HVAC controls.

All par for the course, but I like to drive the damn thing every now and then. I've got another Eternal Project Car™ that I can throw endless center sections at.

And yep, I forgot about the pin holding the rod in place.

-Kurt

 

[khryslerkid]

I hadn't driven it since May due entirely to the dash cluster issue that I had to sort over a few months worth of weekends.

Well at least you know what you're dealing with now. Sometimes we have to learn the hard way and just chalk it up to a learning experience.

Crazy coincidence, I bought a 3.23 sure grip and the ring gear was dated 1964. It had the thrust buttons that I removed to install the newer flange axles with Green bearings, eliminating the tapered axels and upgrading to removable drums.

This was a good thread on this subject and others will be informed on useing pre '64 center sections.

Off topic but what's the trick with inserting the link to your dash cluster? Looks cleaner than copying and pasting the Web link!

 

[cudak888]

Well at least you know what you're dealing with now. Sometimes we have to learn the hard way and just chalk it up to a learning experience.

Crazy coincidence, I bought a 3.23 sure grip and the ring gear was dated 1964. It had the thrust buttons that I removed to install the newer flange axles with Green bearings, eliminating the tapered axels and upgrading to removable drums.

This was a good thread on this subject and others will be informed on useing pre '64 center sections.

Off topic but what's the trick with inserting the link to your dash cluster? Looks cleaner than copying and pasting the Web link!

Let's put it this way: This Satellite has definitely been the hard way to learn the hard way. A '79 Lincoln once came close, but this one takes the cake.

Makes you wonder if 3.23's were common on one of the '64 offerings...

I highlighted my text and then clicked the link shortcut in the forums' word processor. Put in the link, whammo, done.

-Kurt