Hot Rods Need to identify rear differential?

"MOPAR" I am Butch/56sedsendelivery.

 

As said it's a 721, next question it's an open rear, can I make a posi, R part available?

 

Nope posi traction is a gm term. Lol. Yes there are aftermarket traction aids available, stay away from the factory cone style sure grips, they are non serviceable when the wear out. And I agree with the above, sure looks like an 8 3/4”


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thx

 

So I know what not to get per " factory cone style sure grips". Not this? https://www.ebay.com/itm/Early-Mopa...80792908?epid=24025820144&hash=item2ab258d64c

 

It isn't clear in the ad what style it is, if it is a factory sure grip then it is most likely the cone style. It depends what it originated in, as in which center section, if it has clutches behind the side gears then it would be fine, at least rebuildable. I would need better pictures to identify which style it is.

Never mind, looked on a computer not my phone and it is a clutch style so that's good. I would price out new ones however before I paid that for a used one.

 

Hi Butch, u seem to b hip on the Mopar 721 rear i have. Same Ride has Chev front discs w 1/2 -20 lugs studs. I need to know what lug studs r on the the 721 rear. They seem slightly bigger? Do u know what size they r? 1/2 -20 starts less than a thread & sticks

 

Actually, I've only ever owned "ONE" MOPAR, a 70 340 Dart I bought new, right out of high school, and paid cash for it (worked at a Standard Chevron Dealer all through high school as the "night man"). Sure Grip was MOPAR's designation for their limited slip differential. I know because it was on the build order for my Dart; 3.91 Sure Grip, but I don't remember that cost. The car however, cost me $3,410.50, and I'll remember that until the day I die. Have you tried your local, or online, MOPAR source for studs? It should be fairly easy to find out what you have; if the spring pads have't been moved, then it's from a truck, based on the springs over the housing mounting. 1970 was a long time ago for me, and the girlfriend I had at the time, almost killed me, literally; I have never gotten over her, even though she has been married and divorced FIVE times since then, and is easily twice the size she was, and she was only 4"11", and about 110 lbs at that time. Always knew she "took" after her mother, but the heart does't care about those things.
I am Butch/56sedandelivery.

 

One thing to remember on Mopar rear ends, the left side of the axle will have left hand threads on the studs. I don’t know what year this started or stopped, but it’s something to keep in mind.


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Left handed threads, I remember those. I broke 2 studs off in a snowstorm, trying to change a tire on my buddy's truck. He couldn't budge them, so I tired it. We both figured something was terribly different going on after the second one snapped.

 

Now you look for the little L stamped in the end of the stud, eh?