Rear end question: what is a "open" rear end and is it better?

[green69rt]

I've heard that the only stupid question is on that is not asked so here it is.   WHat is an "open" rear end?  Is there such a thing as a "closed" rear end.  What defines it and why is it called "open".  Finally, is "open" better or worse  other types and if so why?

[maxwellwedge]

An Open rear end is something you may end up with when you buy a car off eBay or at an auction....

A closed rear end is when you wont pay for a proper part for your baby.



Ok - Enough joking.

An open rear is a rear without Sure-Grip. A single wheel pull, a one-legger etc.

[RGA]

open === 1 wheel, not possi, BAD
not open, close=== possi, 2 wheels, locker, limited slip, sure grip, traction GOOD

[Cooter]

Some believe that an "Open" rear is better only because it weighs less than it's Sure Grip counterpart. When set up properly, you can run an open rear and plant BOTH rear tires just s hard as any Sure grip.. However, getting the Set up correct is where most feel it's easier to just find a Sure Grip and be done with it.



Set up = Air Bags/Stiffer Spring on side with less traction/Different shocks on each side of rear/etc..

[flyinlow]

Most cars have an open differential. Limited slip was an option on most rear wheel drive cars in the 60's & 70"s  The Suregrip differential increased traction in snow and mud by forcing both rear wheels to drive the car. A car with an open differential can get stuck ,only spinning the wheel that gets the least traction.  Also ordered on some performance car to keep it from doing single wheel burnouts, which slows your acceleration and is very hard on the differential gears.
It works by having a spring loaded clutch between the left and right axles that resists letting the axles turn a different speeds. On dry pavement the tires have enough traction to overcome this clutch when making turns.

Open: no added cost, lets car corner at its maximum without interfering. Probably a few pounds lighter,never weighed them. Can get struck easier in the snow or mud. If you do lots of burnouts, you will get to  learn how to replace the differential gears.

Suregrip: cost more, can slightly put additional cornering loads on the car ( wants to drive both rear wheels at the same speed , it takes power from the car to overcome this)  Helps protect the deferential gears during a burnout, improves initial acceleration by reducing wheelspin. On icy surfaces it can let the back end brake loose especially in a turn or accelerating. When I drive my Charger in the snow and I start to accelerate from a stop sign making a turn it is very easy to slide the backend out or "drift" it. Fun if you are expecting it and have room to do it. In a straight line the Suregrip helps you go in the snow. OK we don't drive in the snow much , but I did drive these things back when they where my dally driver. I have one in my car for the reduced wheel spinning. Mine will make the rear tires skid a little on a road with loose gravel or sand if I am starting from a stop and make a sharp turn. Suregrip cars must have both rear tire the same height. (a spare tire issue)
I have one in my Charger, it is a good thing. If you are just going to cruise around, you don't need one.  

[green69rt]

Thanks for the info folks.  I know what a limited slip differential is just didn't know about the "open" thing.  The Charger I had in my youth in Idaho had no SureGrip but I did drive a lot in the snow but never had a problem.   At that time there was a certain amount of bragging rights associated with having a Sure Grip.  I intend mine to be a driver but it will have a 440 stroker in it for some extra go,  guess I'll have to decide about the rear end later.

[Kern Dog]

Okay. now that you mentioned "Limited slip".......

An OPEN differential is as stated, a standard unit with nothing inside to promote both tires to get equal traction.
The term "Limited Slip" refers to a type of differential that allows one wheel to spin at a slower speed in turns, yet transmits equal traction in straight line. There were many brand names of the various Limited Slip differentials over the years. Chevrolet called theirs Posi-Traction. Ford used the Traction-Lok name. Pontiac had Saf-T-Track. Oldsmobile called it Twin Grip. The Mopars had Sure Grip. These all used Cones, springs or clutches to operate and will eventually wear out. Some can be rebuilt.
Going a step further, there were aftermarket companies that produced units that offered greater durability but they often come with drawbacks for street use. Lockers, Spools and welded "Lincoln Lockers" may be the ultimate in traction, but try driving with one in the rain or snow!   Waaaahhooooooo!!!

[FLG]

Some believe that an "Open" rear is better only because it weighs less than it's Sure Grip counterpart. When set up properly, you can run an open rear and plant BOTH rear tires just s hard as any Sure grip.. However, getting the Set up correct is where most feel it's easier to just find a Sure Grip and be done with it.



Set up = Air Bags/Stiffer Spring on side with less traction/Different shocks on each side of rear/etc..

People dont realize you can get both wheels spinning with an open, but once one gets a little less grip, its over.

[green69rt]

Some believe that an "Open" rear is better only because it weighs less than it's Sure Grip counterpart. When set up properly, you can run an open rear and plant BOTH rear tires just s hard as any Sure grip.. However, getting the Set up correct is where most feel it's easier to just find a Sure Grip and be done with it.



Set up = Air Bags/Stiffer Spring on side with less traction/Different shocks on each side of rear/etc..

People dont realize you can get both wheels spinning with an open, but once one gets a little less grip, its over.

Very interesting!

[SmashingPunkFan]

Is there any way to tell if yours is a surgrip, or open without cracking it open?
Mine is a 8 3/4 diff... just curious

[FLG]

Jack up the rear and spin a tire, if the other spins the oppisite way its open.

[SmashingPunkFan]

Ahh... yes. thank you!