[b-man]

Without traction tires the 8.2 is fine for the most part, with sticky tires all bets are off.

If you plan on a lot of spirited driving go for the 8.5 or best is a new 12-bolt built on an aftermarket housing.

Many 455 cars came with 12-bolts and some the Corporate 8.5, the 428 could be considered being about the same when it comes to your rear end choices.

So many people forget that the rear end needs an upgrade when you build a stout engine. It’s okay to get by for a while with a stock rear end but put aside some money for a good one before you find yourself sitting on the starting line with a broken rear end.

It’s only money.

[dataway]

All good I'm curious too.

[b-man]

Let’s face it.

GM put weak rear ends and lousy brakes along with narrow rims and tires on these cars back in the day. Imagine that a Le Mans had 14x5” wheels and you had to throw down for the GTO just to get 14x6” wheels, pitiful, there wasn’t even a disc brake option until 1967.

These cars with 389/400 cubes and 350ish factory horsepower all deserved a 12-bolt rear for how they were intended to be driven. I bet the additional expense to equip these cars with a decent rear end would have been paid for and then some by not having to replace the weak 8.2s under warranty.

They still never learned their lesson, producing the LS1 cars with their wimpy 7.5”/7-5/8” 10-bolts.

[Jay S]

Wasn’t just GM. Fords factory 9” grey iron differentials only are good for about 400 HP. If you don’t believe me, look up quick performance’s reman 9” grey iron pigs. We have broken the grey iron 9” carrier’s pinion support off, sheared the pinion off in front of the pinion bearing, even split a posi carrier completely in two. I have broke more 9” rear ends than 10 bolt 8.2s.

Even Fords 8.8s the posi and open carrier’s don’t hold up to much over 400 HP. To get them to hold up with slicks, they really need 31 or 35 spline axles and spool, and cover girdle, just like building a 8.5 10 bolt or a 8.875 12 bolt for drag racing. The 9” you have to buy an aftermarket nodular or Billet aluminum pumpkin with a bigger than factory pinion shaft, a complete assembly like that usually starts at over $ 1200 with a cheap spool. They are not cheap to build.

With just a stock converter with 400 HP and slicks the 8.2 should hold up ok if you run a cover girdle, 4 pin posi, and the axle bearings are fresh. Building one to go much quicker than in the low 12s though is a lot like throwing money into a fire.

[Jay S]

There is still a grease spot on the shoulder pulling on to the highway from my place were the last 9” Ford sent the driveshaft and front half of the pinion rolling across the highway!

[1968GTO421]

Originally Posted by Jay S

There is still a grease spot on the shoulder pulling on to the highway from my place were the last 9” Ford sent the driveshaft and front half of the pinion rolling across the highway!

Yikes!