Suregrip and open differential gears

[Nacho-RT74]

I wish to know if pinion and gears are completely interchangeable between suregrip and open differentials no matter the ratio...

A friend of mine think found to me a suregrip carrier to 8.75 axle but 3.91 ratio, and I want to keep the 3:23 ratio from my open differential

[RD]

the pinion and ring gears are interchangeable between any suregrip and open carrier as long as they stay with the same 8 3/4 case (i.e. 741 gears for 741 case).

[Nacho-RT74]

Ok... I Think my buddy found it with case, not just the carrier.

I'll trade this carrier for the NOS 9.25 axle that I have with suregrip, If he accepts of course

[Chryco Psycho]

this works in the 8 3/4 but not nessisarily in th eother Mopar diffs

[Nacho-RT74]

this works in the 8 3/4 but not necessarily in the other Mopar diffs

Maybe is becasue the carrier case is a separate part of the rest of housing and you can change only that !?

[Nacho-RT74]

How many kinds of 8.75 cases exist ? and what are the numbers ?

[Ghoste]

There are three (that I know of) and the last three numbers of the casting code on them are 741, 742, and 489.

[Chryco Psycho]

there are at least 2 more from the 50s 

[Ghoste]

I stand corrected.  Their casting numbers (last three digits again) are 985 and 657.

[Nacho-RT74]

NICE !!!

and absolutelly no one of them are interchangeable parts between them ? or maybe some of them has interchangeable parts ?

[Ghoste]

The carriers should all interchange.  The pinion gears are where the big differences are is my understanding.  That and axle shafts when you are talking about complete housings.  But as far as I know, the actual differential portion should swap.
Am I right?

[Nacho-RT74]

so, as I understood, the different cases makes difference really on pinion... what of course makes that gear will be different also...

BUT if carrier is the same, I could ( as I understood for what you said ), use the carrier from any case and install it on any case and use my actually open differential pinion and gears...

Of course that is if your info is the right one.

[Nacho-RT74]

Ok... look what I found:
http://www.autohobbydigest.com/8_75.html

I have to analize it to get it, but if some of you guys could make me an easier way to understand it would be great LOL.

As I did read, it looks that carriers 741/742 and 489 are completelly interchangeable, including suregrip and open diff interchangeability with only inner axle bearings cup difference... But still I don't understand what I have to do to match with my actually open differential and axles assembly and install it or whatever. What in fact it looks to say is that I can use my open differential case with its pinion and gears, and just interchange the carrier itself, saving the inner bearing stuff.

and as read:
657 is 741 equivalent
985 is 742 equivalent

Both because "Thrust Block Variations" since 1964 ( what I don't know what is )...

[Ghoste]

Well, let's back up a bit.  First, does your buddy have the carrier and case and do you know the casting number of it?  Secondly, what is the casting number off the unit currently in your car?  I only ask because we may be overcomplicating this.

[Nacho-RT74]

LOL... yes is true...
My car is not with me rigt now. will check on monday
The one that I suposselly would get is from a friend of a friend of mines, so he is searching it...

[Ghoste]

You should repost when you get that info then Nacho, but I have a feeling that you're going to okay to swap in that Sure Grip with only minor issues to overcome.

[SpudRacer]

Hate to butt in, but is the old saying that "if you spin one wheel and the other spins in the opposite direction" true for the presence of a Suregrip in my 69?  I shouldn't have one, but if not, I'll put one in.  Thanks for the info.

Tom
Bryson City, NC

[Nacho-RT74]

if both spins on same direction there is suregrip... if only pins one or both on opossite direction there is open differential.

[SpudRacer]

S W E E T ! ! !

Then I already have one!

Many thanks,

Tom

[Ghoste]

Now you need to get out there and abuse it so you can find out if it's still got any life in it.   

[Duey]

Nacho, I think you should have a 489 case...I have a 489 3.23SG in my '73 SE 440.  Then again, I just picked up a 489 4.10 SG from Ron yesterday, so I may have a 3.23 489 coming up for sale real soon...

Cheers,
Duey

[Nacho-RT74]

Ok, no, mine is 741... damn... supposely Low Performance diff.

[8WHEELER]

There is nothing wrong with a 741 case, it will still handle a lot of HP and will most likely
last forever behind a stock engine or mild built 440. I have run them in my Charger
running 12.80's and never had any problems.

Dan

[Ghoste]

I wouldn't lose much sleep about it Nacho.  The 741 case gets a bad rap and it doesn't deserve it.  The Direct Connection manuals used to tell you to use the 489 case for racing because it was stronger and right away everybody assumed that meant the others were no good.  Not true and some people feel the 742 is better than the 489.  Unless you are sticking slicks under the car and dropping it into gear at high rpm, you are notlikely to break it.  The 8.75 is an extremely strong rearend in any of it's variations.

[Nacho-RT74]

well, i'm not loosing sleep about that... is just that everybody wish one step more on performance  even won't use LOL