FireDemonSiC

I want to rebuild the rearend in my car, but am trying to balance it between performance/reliability/cost.

I was initially thinking of doing a full rebuild. Axles, carrier, ring & pinion, bearings & seals and girdle cover.

Now I'm contemplating a budget rebuild. Ring and pinion, carrier, bearings & seals and girdle cover. I know the axles would only be $225 or so more, but depending on labor costs cutting the axles out could make a huge difference.

How well do the stock axles hold up behind a 305TPI, granted everything else is built?

Here is what I DO know about the rearend. It is a 10bolt, not original to the car. I talked to the second owner of the car and he said shortly after he first got it he threw the pinion out of the factory rearend and ended up replacing it with a grand national 10 bolt with a 3.73 limited slip. Now, 3 owners later, it has a 3.23 open diff. I talked to the guy I bought it from (4th owner) and he said he never changed out the rearend so the third owner must have screwed it up and put in a junkyard rear (Made evident also by the chrome diff cover, which owner number 2 said was not there when he sold the car).

Wadebryant

To get the limited slip carrier and 3.23 gears or better, you'd be time and money ahead to source and purchase a complete good used replacement rear end out of a 90-92 Z28 or Trans Am, 9 or 10 bolt. Both are strong enough to handle your 305's power level.

What about your rear brakes? Are they drum? Plan on keeping your current setup?

FireDemonSiC

I don't understand how this would any better/stronger than what I have now. Sure I'm aware there are minor differences over the years like 7.5 and 7.625, gear ratios and posi/open but in the end a thirdgen rear is a thirdgen rear. the casing is fine.

big gear head

Around '89 the 7.5 was upgraded to 28 spline axles from 26 spline. If you get the later rear end then you get the larger, stronger axles too. This is why it is recommended to get the later rear end.

The guy who told you that he installed a GN rear end in this car is feeding you a bunch of BS. A GN rear end will not fit these cars without a HUGE amount of fabrication and engineering.

If you build the rear end that you have now then I recommend a new Eaton Posi, a good brand name gear and the best installation kit that you can get. As for the axles, if your axles are worn then they need to be replaced. It is very common for these axles to wear where the bearings run on them. When this happens then they need to be replaced.

Wadebryant

Your second post helps clairifies your direction. You want a stronger rear end package. Correct?

Have heard it said that a 9 or 10 bolt will live up to the 10 second 1/4 mile rule. Taken with a grain of salt of course. Most will probably suggest that you consider a Ford 9" a GM 12 bolt, or an Strange S60 as dollar wise investment with high power ratio power plants. Most 305's arent producing the levels of torque that one of these rear ends is able to support. However, when you add up the costs to rebuild or beef up a 10 bolt with quality parts, you still end up with a weaker 10 bolt and are just shy of about 1/3 of the cost of a better and stronger rear end.

Good luck

FireDemonSiC

That makes more sense, but remember, I'm not doing the work. A shop is. I'd be interested to see the cost difference of having 28 spline axles installed in my current housing vs swapping in a complete rear from a 91/92 (Which as per big gear head would probably have worn axles anyways) then upgrading the carrier pieces.

Also for the 12 bolt argument, I was seriously considering this approach. But again, It's about a $1000 difference vs strengthening the 10 bolt, and to me, thats alot. Especially if my 305 isn't making use of the 12 bolt abilities.

FireDemonSiC

I kinda suspected that, but never could figure out why he would go on with that level of BS without a cause. He even asked if he could buy the car back. That woulda been more ammunition for me to jack the price up. Maybe he got confused on the model it was taken out of, or was told wrong by some junkyard/shop that just tossed it in.

I never bothered to look up the fabrication/modification process of installing a chrysler rear into a GM car. Didn't know if cutting/welding was involved or if it was as simple as buying a set of relocation brackets, so I never gave it much thought.

Whatever the case, I'm now very interested to pull the casting number off my current rear end see what it turns up. It's on the bottom of the pumpkin correct? The cover looks a tad bit oval so I think It's a 7.5 (Damnit for a second I was hoping it'd have an 8.5).

big gear head

The only rear ends that will fit these cars are the 3rd and 4th gen Camaro and Firebird rear ends. Maybe he got the rear end from a GTA instead of a GN.

FireDemonSiC

Maybe he did mean GTA. But, he stated the car the rear was pulled from was some car from the 70's. Everything else he said was spot on, so either he was told wrong or had a brain fart. Either way, It's def a GM 10 bolt rearend in the car now (Made apparent by the bolts on the cover and the letters, "GM" cast on the bottom of the pumpkin.

Also appears to be a 7.5 or 7.625 rear from the slight oval in the cover and the tiny 'ears' at the bottom of the pumpkin.

big gear head

The GN had the 8.5 rear end and was built from '82 to '87. I don't know what he thought he had, but it wouldn't have fit your car unless it was from a 3rd or 4th gen Camaro or Firebird.