[Verdoro 68]

I'm starting to do some research into upgrading from my 8.2 into something more durable.

I see a few paths:
- Find an 8.5 or a 12 bolt locally
- Moser 12 bolt or 9"
- Strange Dana S60

What I've found locally in terms of 8.5 or 12 bolts have been overpriced and in need a full rebuild/gear swap anyway, so it's making sense to spend a little more to get exactly what I want from the get go.

I'm leaning towards a new Moser 12 bolt since my local options are few and far between. I'm assuming a 9" would be overkill for my application, but I do like the idea of being able to swap pumpkins easily. I haven't heard a lot of folks running S60s.

My car will stay mostly on the street. I just want to the option to take it to the drags occasionally or beat on it without fear that the diff is going to grenade. What should I be considering in terms of carrier type (Eaton, Auburn, TrueTrac), axle splines, etc?

[Gach]

Moser 12 bolt, your combination is pretty well establish so The option to change gears, don’t think is necessary.

[steve25]

Leave the gear change consideration out of the equation.
It’s far easier and cheaper to change tire height to fine tune the gear ratio.

If the axles for now are usable in the local 12 bolt I would go with stuffing new parts in that if it will bolt right in.

If your RAII heads are not heavily ported I don’t think you will harm the 12 bolts stock axles without slicks and a lot of runs.

[JLMounce]

If you're already inclined towards an aftermarket rear, the Moser 12 is a good choice. I have one in the back of my '69 bird. It's one of their muscle pack rears. TruTrac, 31 spline axles, big ford bearings with the chevy special housing ends. It would work really well in your combination.

If you are aiming for more in the future, spec it with a slightly better axle package and upgrade the pinion yoke to a 1350 instead of the 1310 it will come with. The housing itself is good for a lot of power, just limited by the axle and pinion yoke used. Even the basic package is capable of around 600hp or so per my conversations with moser.

[Verdoro 68]

Heads are not heavily ported. Based on my last chassis dyno session, I estimate I'm putting out about 425-435hp and 500tq at the crank (Mustang Dyno numbers were 355hp/450tq w/conservative timing) so nothing too crazy. This combo will likely stay this way for a while since I just built it. I could see moving on to a set of ported Edelbrocks at some point.

With the local stuff - the asking price for the 12 bolts I've seen are $1500 on the low end (non posi) and $2500 (posi) on the high end. By the time I got done building it, I'd likely be in close to what a Moser would cost.

I was looking at the MusclePak setups - looks like the main difference is that they come with brakes?

[Sirrotica]

"Leave the ease of changing ratios out of it", great advice...... That advice is given because changing ratios in a Salisbury style rear axle is a royal pain in the ass. There are different series of differential carriers depending upon what ratio your trying to use. Expensive, and time consuming.

The guys that invented the quick changes decades ago should have listened to that advice............LMAO

If you want to drive a long distance via the interstates, are you going to fine tune it with tires, and wheels off of a semi?

Swapping a third member in a ford 9 inch takes maybe an hour, how long would you guess it takes to change a ring, and pinion in a Salisbury style axle, and at what cost? Even if you only set up one ratio, the cost, and ease of setting up a ford is cheaper initially.

As I have posted previously, the availability, and pricing of parts, and pieces for 9 inch fords make them the SBC of rear axles. There are tons of used stuff floating around that can be bought rather cheaply.

The ford are also easier to set up a ring, and pinion as they are adjusted by screw adjuster inserts, rather than shims to move the ring gear into the pinion for proper clearence, and backlash. I've done both, the ford is easier, and cheaper. especilly if you're paying to have someone do it for you.

My advice would be to price out all of the options, make your decision after checking out the options. You're the only one that knows your plans for your cars usage in the future.

It's your car, your money, and ultimately, your choice.

['ol Pinion head]

It all comes down to the PURPOSE OF THE BUILD.

Read your build thread, I see a footbraked T400 backed 9.5-1 464 with a mild hyde roller cam & what appears to be stock flow '68 RA II heads...

Here's what you got to answer. Is this goal for the GTO a street/occasional strip pump gas low 12 sec 3850 +/- lbs mainly StreetCar????

OR, is your proclivity for the car to be a continual "upgrade" deal where the future eventually years down the road holds low 10's in the quarter mile with a trans brake & slicks?

[Verdoro 68]

Originally Posted by 'ol Pinion head

Read your build thread, I see a footbraked T400 backed 9.5-1 464 with a mild hyde roller cam & what appears to be stock flow '68 RA II heads...

Here's what you got to answer. Is this goal for the GTO a street/occasional strip pump gas low 12 sec 3850 +/- lbs mainly StreetCar????

This is exactly the goal. I don't forsee ever aiming for low 10s at the race track or significantly modifying this combo. For as long as I've owned this car, the goal has always been to keep it a stock appearing car that can handle an occasional runs on drag radials at the Wednesday night drags. This car mostly sees around town cruising and and car shows for which the 8.2 in it would likely serve fine.

[64speed]

Quick Performance 9 inch and done.

[Gach]

Is your head spinning now on making a choice. LOL

[Verdoro 68]

Originally Posted by Gach

Is your head spinning now on making a choice. LOL

It was already spinning. I never really paid much attention to diffs because I never had anything powerful enough to potentially break one!

[i82much]

a 12 bolt would have to be a lot cheaper than a 9 for me to go that route. how much less is a 12 bolt than a 9 inch?

[b-man]

No matter which one you choose this is your chance to get it built to the exact width that centers your wheel and tire assembly inside the confines of the wheel wells for optimum clearance. This allows you to go up by a size or two on the same wheels if you decide to later on.

You will be wearing out a few sets of rear tires I’m positive of that.

If they’re a little too close to the fender lips which is usually the case you now have a chance to move them inward exactly the right amount.

Analyzing the factory-look theme of your build I see the Moser 12-bolt as the one that best fits your car.

Good luck and have fun.

[i82much]

ah ... so the appearance is why people go with the 12 bolt instead of a 9 inch or 60 ...

[Gach]

Or maybe it’s the stigma of Ford 9”. Just suggesting.

[b-man]

Originally Posted by i82much

ah ... so the appearance is why people go with the 12 bolt instead of a 9 inch or 60 ...

Sometimes perhaps.

Some people put the 9” in their cars just for bragging rights and just to say they have one, whether they need the upgraded strength (there are many versions both weak and strong) or just like to run the same style rear as many full-on race cars.

I can remember calling up the H-O Racing tech line back in the early ‘90s where Ken Crocie would answer technical questions for his customers. I was telling him about my car and mentioned it had a 9” and he said he didn’t like them and preferred the 12-bolt. If he did tell me the reason I’ve forgotten it, but anyway everyone has their preferences.

Both myself and my friend who I traded one of my cars to for my first Pontiac (which was a 1964 GTO I later learned was a clone) were really into drag racing and having a Ford 9” we thought was the greatest thing in the world. The GTO when I got it in 1989 had a narrowed Currie 9” with a 31-spline Traction Lock and 3.25 gears, a Doug Nash 5-speed behind a ‘69 RAIII 400. All top-shelf stuff for the time.

After a few years I started bracket racing the GTO running a 455 and TH400, it wasn’t long before the clutches inside the Traction Lock were worn to the point where where it wouldn’t burn both tires anymore. I pulled the pumpkin and paid someone to install a Detroit Locker and 3.89 gears. After that I never messed with it, racing it for about another 9 years before finally selling the car.

The 9” fit the theme and purpose of the car and at the time it was a better rear end than a GM 12-bolt but times have changed and now the aftermarket complete new rear ends afford you many more choices. Back then everything was built off of junkyard housings and center sections for the most part, not brand new upgraded components like you can buy today.

[Jay S]

A moser 12 bolt would be the way to go if you want to throw money at it and keep it looking stock. OEM 12 bolts are generally too pricey, by the time you make upgrades to a 1200 open rear end with 2.73s your most of the way to the cost of the Moser, and the Moser is quite a bit stronger.

If you have a N case 8.2 I would get a TA cover and run it and not replace it until something breaks, in the 12s with drag radials, that might be never. But it could be the first pass too, that is drag racing..LOL

The 3.36s seem to be the toughest gear set in an 8.2, a little stronger than 3.55s. Also versus OEM gears, the aftermarket gears also do not have some of the tapers on the pinion machining and are a little stronger. See the photo..

The offset of the 9” rear end is pretty noticeable under an A body. If your going after a OEM type look, it does not fit that. We fabricated had a 9” in a A body before all the kits were available. We did an 8.75 Mopar in an A body also. The 9” with upgrades for power get’s pricey pretty quickly, nodular case with the bigger front bearing support are pretty important upgrades.

For the money, it is hard to beat buying a 8.5, then depending on how quick it is do other upgrades. I bought a 8.5 a few weeks ago from a 72 Cutlass for $350. There was a salvage years that had several 8.5s from 72 Chevelle’s and Buicks, he wanted $350 also. I have seen some asking $500. There were several million of those 8.5s made in 71 to 72, you just have know where to look for them, they put them in every 2 and 4 door combo of A body there was later end of 72. They cost a fraction of the price of a 12 bolt, parts are cheap too.

I have broke quite a few 9” rear ends. I split one grey case open and broke the back pinion support off with a 300 6 cylinder. Split the carrier in 2 on another. I have 2 friends that have broke pinion shafts. JMHO. The Ford 9” are the most expensive rear end to build properly. They run pretty hot compared to other rearends, the worst part of the 3% loss in efficiency shows up in the form of heat.

[242177P]

For a RA II, I'm leaning towards the 8.5" - purely because aesthetics. Take a grinder to one and most folks won't know it isn't an 8.2, "whoa, it still has a 10 bolt". Sneaky. Assuming Ol' Pinion head has one on his racks, he could be a one-stop shop for you. Road trip?

12 bolt is my second choice. Period correct upgrade. Still GM, nobody is going to hold their nose. Perfect if you're wanting to impress the folks who are impressed by the number of cover bolts. The 9" just screams "I've been modified", and the bread and butter parts aren't bulletproof.

[Verdoro 68]

Originally Posted by Jay S

If you have a N case 8.2 I would get a TA cover and run it and not replace it until something breaks, in the 12s with drag radials, that might be never. But it could be the first pass too, that is drag racing..LOL

I have a '69 XH code 3.55 4-pinion posi with a nodular case right now that's not original to the car. It was rebuilt about 10 years ago. The conundum is it's a relatively valuable rear for someone restoring their car. Would a $200 TA cover really add that much strength to it? It would be a shame to blow it up when I could sell it and recoup some of the cost of a more stout rear end.

Originally Posted by Jay S

For the money, it is hard to beat buying a 8.5, then depending on how quick it is do other upgrades. I bought a 8.5 a few weeks ago from a 72 Cutlass for $350. There was a salvage years that had several 8.5s from 72 Chevelle’s and Buicks, he wanted $350 also. I have seen some asking $500.

If I could find a core for that price, the decision might be easier. I was thinking they'd be easier to find around here, but maybe I'm not looking in the right places.

Agree on a 9" screaming "modified: which is why I was leaning towards the 12 bolt. "Keep your GM car all GM"

[kyle_blake]

What is a TA cover?