Sure Grip power limits

[big_shmoop]

I'm looking at different options for my 8 3/4 rear end. It will mainly be a street car/Saturday night special, but I also plan to take to the track from time to time. While at the track I plan to get a set of Hoosier 28/9-15 slicks to get the most traction. On the street I'll be running 275/60-15 radials so they'll break loose fairly easily.

I know weight+torque+traction=broken parts so my question is at what power levels do guys switch from Sure Grips to spools on B-body street/strip cars? I know if you ask 10 people about driving spools on the street you'll get 10 different answers....so we can leave that for another discussion. I'm aware it's not ideal but it's not a daily driver so if that is what it takes to increase durability, so be it.

I've read that Power-Lok's are stronger than cone style, but how about Eaton Trutrac's, Strange S-trac or Detroit Lockers? While this is regard to my 8 3/4 setup, I'll also be faced with the same question when I go with Dana or Ford 9" in the future.

I'm looking for peoples experience and thoughts. I've gotten some ideas from some others but looking for more feedback. Thanks.

 

[cryplydog]

Auto or 4-sp?

 

[mopar 3 B]

The housing will give before the sure grip does. Distortion will need to be addressed before wasting money on internals.

 

[big_shmoop]

Auto or 4-sp?

Sorry, thought I put that in the original post. It's an automatic. While not quite as much drive shock as a 4-speed I just wanted to see what others have experienced especially with launches on slicks.

The housing will give before the sure grip does. Distortion will need to be addressed before wasting money on internals.

What would you consider wasted money on internals? I've looked into bracing and housing modifications, but at that point I'll probably just switch the entire housing (Dana or 9").

 

[PurpleBeeper]

Well, I'll take a stab at it...... 750 hp on a 8-3/4" would be my guess. The back-bracing is pretty cheap. Spools don't like to turn corners without breaking axles. Lastly, and you probably already know this, you need hardened axles to run slicks.

 

[Daves69]

IMO, Chasing wheel studs, u-joints, then ring gears and axle splines. Either sure grip is tough enough when in good condition. Power-loc I believe will be more serviceable than a cone in the long run.

 

[big_shmoop]

Well, I'll take a stab at it...... 750 hp on a 8-3/4" would be my guess. The back-bracing is pretty cheap. Spools don't like to turn corners without breaking axles. Lastly, and you probably already know this, you need hardened axles to run slicks.

The only reason I'd switch before going too crazy on modifications is someone once told me, "You can do all that and spend your money on a 8 3/4 that MIGHT live...or you can just spend it on a Dana and forget about it."

Realistically right now and in the near future my car isn't going to be making the kinda power where I'll be overly concerned with the rear end. But in time as I continue to build it up and take it to the track more often it's something I want to keep an eye on. By no means do I feel the 8 3/4 is made of glass, but I know that when you start hooking a heavy car sooner or later you'll find the fuse in the line.

IMO, Chasing wheel studs, u-joints, then ring gears and axle splines. Either sure grip is tough enough when in good condition. Power-loc I believe will be more serviceable than a cone in the long run.

Good points. Studs and u-joint are already being address when I take things apart. Thanks.

 

[mopar 3 B]

Sorry, thought I put that in the original post. It's an automatic. While not quite as much drive shock as a 4-speed I just wanted to see what others have experienced especially with launches on slicks.



What would you consider wasted money on internals? I've looked into bracing and housing modifications, but at that point I'll probably just switch the entire housing (Dana or 9").

If the housing is allowed to flex things get out off alignment thats when most breakage occurs making any improvements to the internals a waste of time and money. This occurs at over 600 hp if power gets to the ground.

 

[big_shmoop]

If the housing is allowed to flex things get out off alignment thats when most breakage occurs making any improvements to the internals a waste of time and money. This occurs at over 600 hp if power gets to the ground.

I see what you're saying and agree.

My main concern will be launches at the track. While damage can definitely still occur on the street, the tires will break loose to long before to help soften the stress.

I've seen the weld on braces available, how do they hold up?

 

[lewtot184]

i don't think any of the 8 3/4 "sure-grips" are long lifers with sticky tires and good power, especially the cone types. even if you find a good differential, and detroit locker may be the best, the caps break or the ring/pinion get clobbered. i've seen sure-grips mess up at less than 400 rear wheel horses. you can toss a lot of money in and 8 3/4 and break it. put the same money in a dana 60 and basically forget about it.

 

[cryplydog]

The motor company used the Mopar Dana-60 after 375 HP.

 

[1967coronet]

I was just looking through my Classic Industries Catalog and Moser has 8.75 and Danas listed in there. What caught my eye was the Dana complete your choice of ratio was $300 cheaper than the 8.75

 

[mentor70]

the Auburn True Track is the best diff you can buy for a 8.75.

it has no clutches to ware out, no cones that weld to the housing. and needs no special additives....but its 550$

 

[2quick]

what I'm running! 8 3/4, Detroit Locker, 4:10's, Back and Top Braced, Moser Axles. I've also heard that the housing fails first so I tried to do my best by boxing it in as best I could. Car making almost 700hp and should run low 10's but I'm still hopeful for the best. I bought this rear already together and kinda cheap, then braced it myself but if I were to do it from scratch I would have probably went Dana.

 

[big_shmoop]

Looks great, I hope it holds up for you.

 

[5.7 hemi]

The clutch style will last a long time, just remember that back in 64-65, the Dana 60 was not available and you had max wedges putting down some serious power.