I currently have a 8.2" (posi) rearend in my 1968 Skylark Custom. I have two options. 1. Rebuild the existing rearend. 2. Replace the existing rearend with a rebuilt 8.5". I'm currently working 70 hours a week so I'm sending this out to be done either way. Money isn't really an option unless we're talking a difference of more then 500 bucks or so. I have a estimate for $1000 which includes removing my existing rearend. rebuilding the existing unit. Changing my gears to something a little more aggressive. Chaning my speedo gear if needed. Replacing all the u-joints, bearings, etc. I can pickup a rebuilt 8.5" rearend fairly cheap on ebay, but then we're talking shortening the driveshaft, balancing and still doing all the other labor (u-joints,etc). Question is this: Whats the pros/cons of upgrading to a 8.5"? How much HP does my engine have to produce to be a factor in needing the bigger rearend? (if I'm pushing it) Is there any problem with using a 8.2" rearend? (other then the cost of rebuilding it)
8.2 cons: poor repair parts availability, and weak for higher HP builds. 8.5 pros: excellent parts/gears availability, and best choice for a performance build. You don't say what you've got going on under the hood, and that is the big factor in this decision. If you're running a mild 350 or 400, the 8.2 rebuild will be just fine. If you've swapped a 455, chances are you'd be better off with that rebuilt 8.5 rearend. I have a 455 swap planned, and will end up with an 8.5 rear most likely. Currently have a 2.56 posi out of a 69 Skylark Custom.
I just got done changing my 8.2 to an 8.5 in my 70 GS455. I had to shorten the the driveline and balance it for about $85.00. The rear end came out of a '71 Skylark. Other than that it was a bolt up. Dave
If you are up grading for more power and spending 1000-1500 your best bet would be a 12 bolt with eaton posi and 30 spline axles. More parts available! More gear available. :TU:
Not true, until one spends near $1750+ on a professionally built tapered bearing bolt-in axle 12 bolt with custom axles & a HD 30 spline new Eaton carrier, one only has a c-clip axle 12 bolt. Have built too many, the days of core 12 bolt A-body housings running $50 is waaaaay past. Upgraded to HD 30 spline Eaton carrier with new 30 spline Mosers, a factory tapered bearing bolt-in axle 8.5 rear can be built up & bought for under $1400. Both GM rears will hold up to same punishment, just costs more with the 12 bolt due to excessive housing cost, & cost to install new hsg ends. Got Posi? :3gears: Roger
eljefe98 Until you ck what ratio of gear is in your rear, don't discount your factory posi BUICK 8.2. Its not like you have a StageII under the hood. Best case scenario, you have a 3.23 4 pinion '68 BUICK 8.2 under the car, & the rear needs freshening with new axle bearings, wheel studs, seals, possibly carrier bearings/races. Talking $250-350 worth of diff work, vs stepping up for one my entry level $895 blueprinted 8.5 posi A-body rears. Got Posi? :3gears: Roger
