My first time with big power. '68 Dart, 606hp sbm, Tremec, Gerst suspension. Want to run autocross, but streetable. Do you think an 8 3/4" is a good choice? Will it handle 600+ hp? Maybe a "built" 8 3/4"? What do you think? Thanks.
I've never seen it as the "heritic" although I know what you're sayin. Too many chest thumpers think "Mopar or nuthin" and in some cases they are just plain wrong.I think that if a dana has a gear ratio you can live with, i would go that route, rather than put a bunch of money into an 8 3/4. I realize you are talking street use and autocross rather than high traction/high stress drag racing app, but I still don't care for 600hp/manual trans/ 8 3/4 combination.
Then there is always the heretic option.... a nine inch. Much better ratio selection, replaceable center section, lots and lots of strength upgrades available, and can be built much stronger than a 8 3/4 (my opinion).
Mopar is my favorite brand, but I like to think I'm open minded about rear ends. I currently have a Dana suregrip, an 8 3/4 locker, a nine with a spool, and a nine with a locker in use.I've never seen it as the "heritic" although I know what you're sayin. Too many chest thumpers think "Mopar or nuthin" and in some cases they are just plain wrong.
I've always thought the 9" was in the same favor as the early Hemis. They will go good in anything. Looking back at hot rod history, the rear end of choice was the Oldsmobile third member style, before the 9". They were under everything from street cars to early fuel rails.
The 9" has SO many available ratios and upgrades and the parts availability is simply off the scale. They are stupid strong even in stock form. If you use one and have a drive line failure, it probably AIN'T gonna be the rear end.
And of course there's that cool bench racin thing when somebody asks you "Hey Rob, what rear end you got under that?" Somehow when you say "9 inch" it just sounds cooler. lol
It’s more of the amount of torque vs weight and the “Hook” of the vehicle and of course, the amount of abuse. This is a very blurry line to have anyone make a call on. It seems that around the 600+ ft. Lbs. of torque and a 3600 lbs car, the ghost is given up after a short time. Sometimes more, sometimes less. Dropping the car weight would help a lot in longevity as well as beefing up the rear.My first time with big power. '68 Dart, 606hp sbm, Tremec, Gerst suspension. Want to run autocross, but streetable. Do you think an 8 3/4" is a good choice? Will it handle 600+ hp? Maybe a "built" 8 3/4"? What do you think? Thanks.
I tell you what comes to my mind when you said it like that. A beefed up 8 1/4.The stronger the rear axle, the more its going to weight. The more weight, the more poorly its going to handle. For autocross it would be best to back off max torque and horsepower and build a engine with good torque matching the rpm it comes out of corners at so it pulls hard and match the lightest rear axle that will handle that power.
I agree, or an 8 3/4 with aluminum center section, beefed up housing, caps and axle. All the same issues with an 8 1/4.I tell you what comes to my mind when you said it like that. A beefed up 8 1/4.
Heck if I know, but honestly, a 9" ain't gonna lose him any races. It's really splittin hairs. Now, a Rockwell 2.5 ton axle is another thing. lolI agree, or an 8 3/4 with aluminum center section, beefed up housing, caps and axle. All the same issues with an 8 1/4.
really, what is the tipping point from handling to horsepower/ torque in autocross?
There is a certain amount of accuracy to this but the way you out it, it seems over stated. There is additional weight but not at a serious penalty. Drag racers can attest to this. Any additional weight can be wrote off as a reasonable penalty worth having in exchange of durability. The weight is unsprung.The stronger the rear axle, the more its going to weight. The more weight, the more poorly its going to handle.
While an advantageous move, this is really hard to do from a new guy point of perspective. Changing conditions would have constant changing of equipment. Knowing the car and track as all as the engine power curves are where this all starts never mind the equipment being used. Just where this area of to much power is can not be determined by internet chatter.For autocross it would be best to back off max torque and horsepower and build a engine with good torque matching the rpm it comes out of corners at so it pulls hard and match the lightest rear axle that will handle that power.
215 bucks from US Powertrain. Aluminum 9" case. Free shippin, even. lol.....and if you have a typical front-heavy weight balance, a little rear-end weight won't hurt.
And since aluminum 8 3/4 centers haven't been made for about 20 (or is it more?) years, an aluminum nine center is probably about a quarter of the money of an 8 3/4.
I like Mopar parts in Mopars...kinda like how I like Ford Parts on the ocean floor ....and Chevy parts deeply burried in the backyard..