Strongest 8 3/4 sure grip unit

[440dartswinger]

Who makes the strongest 8 3/4 aftermarket sure grip unit? I tore down my rear end a couple of weeks ago, and I found that there was a crack in the stock sure grip housing on my 8 3/4. How much horsepower can an 8 3/4 handle with aftermarket parts? 

[73swinger]

I've heard 700, Do you have the housing braced? apparently they can flex quite a bit and cause failures

[mopowers]

HP isnt the only limiting factor.  The weight of the car and whether or not you're using a trans brake has a lot to do with it as well.

[Womanator]

I would think a transbreak would destroy an 8 3/4.in anything over 3000 lbs with anykind of hp.

[PureGTS]

  Aftermarket 35 spline axles, the new aluminum 3rd member housing, the new trick of the week housing, the beast spool in the world (pick your favorite), or any locker/SG/LSD, whatever. The ring and pinion are still the same design and material. Period. If youre making decent power, near 650-700 or planning on going bigger on HP someday (who doesn't!?!?) get a Dana! With all the money you'll spend getting a 8 3/4 to try to survive, you could have had a Dana and been breaking stuff other than the rear end.
  Getting back to the 8 3/4, if the gear teeth don't fail, the Diff' bearing caps do. One fix for the caps was to put bolts that but into the center of the bearing caps for support. Like the trick covers for the Dana 60's, 12 bolts, etc. Yes, that requires drilling into a non-leaking housing and giving the oil access to an escape point. I've also seen heavy caps made and used, but that just seemed to direct the disaster back to the gear teeth again. 
  Mopowers is dead on it too; If your car is a 70 Plymouth wagon (4480lbs) with a big block and 150 shot of NOS you may want to get more axle under there as that's a lot of stress against your 8 3/4. Not to mention with slicks and a little traction.

[440dartswinger]

The 8 3/4 is going behind a challenger with no transbreak and a 440, so it is around a 3600 lb car. I have no plans for a transbrake and I have not tubbed it, but I did buy some 9 inch slicks for it a couple of weeks ago. I also bought a Dana 60 from a 3/4 ton truck several weeks ago, and I have come to the realization that I am not going to be able to build the Dana for much less than $1200. I have a bunch of 8 3/4 chunks sitting around and I was just curious as to what horsepower some of the aftermarket axles and suregrips would withstand.

[jyrki]

We have about 10 years of experience with realitvely high powered cars with 8 3/4's. In my opinion, it doesn't matter which cure grip you have, most likely it isn't going to be the sure grip that breaks. We have used both factory cone and plate style without any problems. Both have been used in 700+ hp 3300-3600 lbs street & strip cars with M/T ET Streets adn no trnasbrake, and both have run around mid 9's in the 1/4. During this 10 years with two cars and two drivers, we have experienced one gear ratio failure, and rebuilt them two times each because the bearings, ratios etc., were finished, and howled like a wulf. There was nothing special in either, only aftermarket axles, 30 splines. 60 ft's were in the 1.39-1.40 range at best. However, if you have to start from a scratch, I would go either with a Dana or a 9", just to be sure. Do it once right, is the way for a poor guy to do things.

[Hemi GTS]

Two years ago I installed an Eaton Tru Trac, and I have to say this is one fine piece. No clutches or spider gears. It works with a spur gear configuration that splits torque equally to both wheels on acceleration.It also performs as smoothly as a open rear on turns. I put this in a 71 demon 391 rear ratio and it has been run at a local track with 10 inch slicks. The motor is a 360 Magnum crate 380 horse. Here is a link to a chart that shows durability.  http://www.eaton.com/EatonCom/ProductsServices/PerformanceProducts/IndependentTesting/index.htm


Summit Racing  http://store.summitracing.com/egnsearch.asp?N=700+314530+115+4294902583

[GON_RACIN]

http://www.nationaldrivetrain.com/shopsite_sc/store/html/page44.html

[496dart]

My opinion .......you are pushing it if you have more than 575hp or so  in a medium/heavy car ,  UNLESS  you have it backbraced / great internals ,  and aftermarket caps.

My 8.75  lasted  less than a full season in a 3300 lb  car  with  "maybe" 580hp . It was freshly rebuilt.


If you want to save yourself  future headaches in this situation ,  get a Dana 60 .  If you can get REAL  good deals on parts ( maybe a good used ring/pinion)  and a cheap truck housing  you can do it for around a grand.

[JOEYMAN]

I'm going with a dana 60 for my car. We will have it complete here in a few days or so.I'll have pics very soon of my set-up under the car. We are waiting for the driveshaft right now. It shipped thurs so it should be here early this week.

I went with a D60. 35 Spline strange axles. Richmond 4.10 gear and a Detroit locker. Also got 5/8 wheel studs. and a nice shiny stainless rear-end cover.

His is what happened to my 8inch.



Here is the D60 back from the sandblast guy ready to be welded up. We narrowed it to fit my car. It is already assembled and under the car painted. Just waiting on the Driveshaft. I'll have pics real soon

[PureGTS]

JOEYMAN - That's absolutely brutal! I hate to think how much money you had in that. I know the 9"ers are a bit pricey compared to everything else. My condolences to FoMoCo.

440DartSwinger - You should be just fine with any OEM unit. Just make sure you at least get aftermarket axles of somekind. Resplining is cheap and so is the product. If you weren't trying to get traction resplining isn't bad. But traction brings with it its own problems (see pic). I did this to an OEM B body axle, the left one of all things, launching the car (3535lb w/driver) with 4.88's, a 4 spd and 10.5 slicks. Two weeks of street driving later, the 4 pinion Dana clutch type (Trac-Loc) LSD broke a tooth off the side gear. The clutch type is supposed to be the better one since it has 4 pinions (spider gears) to handle the load as opposed to just two in the cone type. We attribute failure to the gear being cracked from the initial breakage at the track.
  Traction is cool and very desirable, but it is looking for the weakest link...  constantly. Get a good loop too.

[383man]

I just put a Detroit Locker in my 8-3/4 and I love it !   Ron

[mopowers]

JOEYMAN - That's absolutely brutal! I hate to think how much money you had in that. I know the 9"ers are a bit pricey compared to everything else. My condolences to FoMoCo.

440DartSwinger - You should be just fine with any OEM unit. Just make sure you at least get aftermarket axles of somekind. Resplining is cheap and so is the product. If you weren't trying to get traction resplining isn't bad. But traction brings with it its own problems (see pic). I did this to an OEM B body axle, the left one of all things, launching the car (3535lb w/driver) with 4.88's, a 4 spd and 10.5 slicks. Two weeks of street driving later, the 4 pinion Dana clutch type (Trac-Loc) LSD broke a tooth off the side gear. The clutch type is supposed to be the better one since it has 4 pinions (spider gears) to handle the load as opposed to just two in the cone type. We attribute failure to the gear being cracked from the initial breakage at the track.
  Traction is cool and very desirable, but it is looking for the weakest link...  constantly. Get a good loop too.

Isn't the 4-pinion diff the "Power-loc?"