489 sure grip

[Hopalong]

Has anyone used the Detroit Locker posi for the 8 3/4 diff?  I picked up a 489 case with weenie gears and open diff at a swap meet.  I plan to rebuild the whole thing, but the MP sure grip is money nuts expensive!  Just curious about other options.

[Carlwalski]

I just purchased this set up from Mancini for mine. 
I needed a 3:91 crown & pinion so thought I'd go the whole 9 yards. 


I purchased the top item. http://store.yahoo.com/chucker54/comcen.html
Precision 3:91 gears, Auburn posi with 30% stronger cogs for a 7290 yoke assembly.

[Hopalong]

That's a nice rearend NZ..........er........did that sound right?  I was thinking 3.55's with some sort of sure grip.  I have seen the ads for detroit locker centers for about $450, auburns for $400.  Just looking for input on any experience for either two.

[MyMopar]

I don't know if this helps but I am running a full detroit locker in the front end of my Jeep.  The design has been updated to a "soft" locker which means that the engagement isn't harsh or noisy, as much.  Very reliable and very very strong.  I wouldn't see a problem going with one for our cars.  Just be careful on wet/slippery roads and taking corners, throttle input will dictate what happens next.   

[zerfetzen]

Not to hijack this thread, but here's a question:

What would you say to someone who tells you an open rear is better than sure-grip as a daily driver for a hot rod?  I have a mechanically-inclined older friend who's built many rods, and says that an open rear is the way to go, that posi (I know that's Chevy, just a shorter word) has a lot of problems with it.  He says it's great to go in a straight line, but bad for anything else, and he built a car with probably 500+ hp that did wonders roasting them down the road with an open rear.

I'm pretty sure we (all of us rod builders) don't want to buy used posi's unless we know how to rebuild them, so it seems that if we want posi, we're stuck spending $400+ for an Auburn, or probably more for a detroit locker.

I guess I'm asking, why choose sure grip over an open rear?

[Carlwalski]

I guess for many it's just a logical answer to traction. 

[mrbill426]

Not to hijack this thread, but here's a question:

What would you say to someone who tells you an open rear is better than sure-grip as a daily driver for a hot rod? 

For our project we have an open 3.55 for the highway cruise and a 4.30 suregrip to swap in for the track;  both are '489s

 

[ShelbyDogg]

zerftzen,
for everyday driving an open is the best. Going around turns it's the smoothest for all the pinion gears. With a posi, clutches are trying to break free to let the outside tire spin more than the inside one, when turning. For all out performance, noise, smoke, and traction, the posi is better. How ofter has your open rear end smoked both tires?  When the streets are wet or dry and you want to power slide the rear end around a corner, the posi wins everytime. But let's say your mom is driving your car around a turn and she suddenly hits a slick spot, one tire spinning is alot better for her than both tires spinning and spinning her around.  So what that means is for that older guy that likes open rear ends, he knows his limits and doesn't power slide his car anymore.  What type of guy are you?

To get back to the topic, the locker is good because it only locks under power and acs like an open when not needed. The older ones used to Click going around turns. Like a ratchet. I saw one on Hot Rod TV that energizes like a posi when 12v is applied to a coil in the pumpkin. Nice piece.

[MyMopar]

To get back to the topic, the locker is good because it only locks under power and acs like an open when not needed. The older ones used to Click going around turns. Like a ratchet. I saw one on Hot Rod TV that energizes like a posi when 12v is applied to a coil in the pumpkin. Nice piece.

That is the Auburn Ected, I have that in the Ford 8.8 in the rear of my Jeep. It is limited slip when it isn't "on".  I did manage to blow the spyder gear on it but then again I wasn't anywhere near a paved road 
In any case a sure grip rear really has no difference on the street except for corners and wet/slick roads.  The additional traction a sure grip adds is the whole point.  You will notice a sure grip more in a manual than an automatic.  The locked rear still allows one tire to spin faster than the other, otherwise it would be a spool.