8.5" rear strength
- Thread starter marcar1993
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As others have said, those 8.5s live behind GNX Regals and F-bodies taking lots of abuse. If you get/have a good donor, with the rebuild you've described, unless you are going to beat on it severely - regularly with tons of torque it should work just fine. Torque matters more than HP yet they are always rated by HP.
Since I don't trust the factory internals, I am rebuilding my 442 with the Eaton Truetrac, Moser 30s, going to a 1350 30 spline yoke and drive shaft, 3.42 [that I know are] high quality gears, and indirectly solving the C-clip breakage safety problem by doing drum to disk in back too while adding some vertical and fore/aft strength bracing to the build.
If I ever get it done . . . [long story I will spare you], I am perfectly confident it will hold up behind my big block. Of course, my donor was free since it came in my 442 but, with $125 LPW bracing for more fore/aft and center strength, UMI claims some added vertical strength comes along for the anti-sway ride with their modern design that clamps the axles forward and up to the frame instead of just tying the 2 lower control arms together which I never understood [??], $150 for blast and coat, $600 worth of high quality internals/bearings. I'm not counting the beefier shaft, drum to disk, or the new sway bar costs as I would do that to whatever rear I decided to use, I will have about $1000 total in just the rear end if I finish the assy, about $1250 if I hire it done and you could cover most of that selling your 2nd 8.5 if it's decent.
Going 9" is the safest thing to do if you are going to the track often and dumping the clutch to slicks with a high torque setup. But, done right that is more like $3500. Watch the nickle/dime adder stuff! I think you can make the 8.5 live . . . on a budget.
Since I don't trust the factory internals, I am rebuilding my 442 with the Eaton Truetrac, Moser 30s, going to a 1350 30 spline yoke and drive shaft, 3.42 [that I know are] high quality gears, and indirectly solving the C-clip breakage safety problem by doing drum to disk in back too while adding some vertical and fore/aft strength bracing to the build.
If I ever get it done . . . [long story I will spare you], I am perfectly confident it will hold up behind my big block. Of course, my donor was free since it came in my 442 but, with $125 LPW bracing for more fore/aft and center strength, UMI claims some added vertical strength comes along for the anti-sway ride with their modern design that clamps the axles forward and up to the frame instead of just tying the 2 lower control arms together which I never understood [??], $150 for blast and coat, $600 worth of high quality internals/bearings. I'm not counting the beefier shaft, drum to disk, or the new sway bar costs as I would do that to whatever rear I decided to use, I will have about $1000 total in just the rear end if I finish the assy, about $1250 if I hire it done and you could cover most of that selling your 2nd 8.5 if it's decent.
Going 9" is the safest thing to do if you are going to the track often and dumping the clutch to slicks with a high torque setup. But, done right that is more like $3500. Watch the nickle/dime adder stuff! I think you can make the 8.5 live . . . on a budget.
That's a bad *ss Regal...love it! What are you running for a rear end in that pic?
As far as real world experience, here’s mine. I have a GN 8.5 in my SS with 3.73’s, Detroit Locker, Moser axles, rear cover with cap supports, and axle tubes welded to the center section. I’ve had this rear in it for 15 years now with a 406 SBC that I keep hopping up. I drive it pretty hard and usually take it to the track a few times a year, the last couple years leaving on a transbrake with 28x10 slicks then spraying with a 200 shot as soon as I hit 2nd. To date I’ve never had any part of the rearend break on me. Maybe I’m just lucky IDK, just my experience. When the engine gets switched over to the F2 Procharger assisted 406, then it will probably be time to 9” it.
The 8.5 is pretty stout, the bearings are the same size as a 12 bolt.
Basically it's a 12 bolt with ten ring gear bolts.
That's a slight overstatement but unless you intend a LOT of serious horsepower applied violently on a regular basis you'd be fine.
Given c clip eliminators of course
Basically it's a 12 bolt with ten ring gear bolts.
That's a slight overstatement but unless you intend a LOT of serious horsepower applied violently on a regular basis you'd be fine.
Given c clip eliminators of course
That was defiantly an epic failure. Wish I could really look at it to see if it was a driveshaft failure (Drive Shaft Critical RPM) or the rear. Seems he was trying to push a lot HP through a basically stock 9 in - stock yoke, pinion bearing, and like to know what housing. I've run 9in rears in everything I've run including my dragster, built to the HP expectations. That being said if I were in your shoes I wouldn't have any problem running the 8.8, or the 8.5 before I laded down that kind of money. Anubis - yes 9 in.
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