Opinions needed

Building my first gen toward the protouring style. I do not race.

Question: do you need a 12-bolt for a protouring? Or is it only needed for drag racing launches?

THX
-Rob

I don't think it's really needed for pro-touring. Unless you have slicks, its even hard to destroy a 10 bolt. If you need a new rearend and want to save a few bucks, I would get a 8.5 10 bolt, from a Nova.

Mike

If your just going for the look, you won't even need a posi rear. One tire on fire is much more spectacular if your audience is in the right (correct) side of the car.


Larger Dave

Needed or not, doesn't a 12-bolt go better with the pro touring "image"?

yes it does and give you a better traction advantage
I just ordered a rear from Moser with a detroit tru trac differential.
It give you straight line performance like a locker and cornering performance like a open rear.
Best part is that there is no clutches to wear out.
its also a couple hundred cheaper than a eaton or aurburn rear.
I bet youll want a rear gear around 3:08 or a bit lower for the pro touring.

I bought a Moser 9-inch with tru-trac 3.50 posi. I love it. Worked great with the Hotchkis system. Im still tuning my Bowtie Overdrives stage 2 2004R, which is also working awesome. In retrospect, I should have gone with 18's instead of 17's...

Opinions needed

Building my first gen toward the protouring style. I do not race.

Question: do you need a 12-bolt for a protouring? Or is it only needed for drag racing launches?

THX
-RobIf your 10 bolt is working okay now, it would be fine for a pro-touring car. Pro-touring is about modern handling, long distance comfort and reliability. As a result, most pro-touring cars have extensive handling modifications (suspension and steering), a modern overdrive transmission and creature comforts (modern seats, sound insulation, a decent sound system, etc.). There is no "requirement" that you have a 12 bolt to be a pro-touring car.

I have an 8.2" 10 bolt in my car with a new Eaton posi, forged axles, new bearings throughout, a "structural" rear cover and 4.11 gears. The 4.11's are, effectively, a 2.05:1 final drive, given the 0.5 overdrive 6th gear in my T56.

If you are on a budget, there are better places to spend your money than upgrading to a 12 bolt. However, if you are going to rebuild your rear end entirely, I would advise going to at least an 8.5" ten bolt and gears that, when multiplied against the top gear in your transmission are no lower numerically than about a 1.90:1 effective final drive ratio. I do about 72mph at 2,000rpm with an effective final drive ratio of 2.05:1.

Finally, if you stay with leaf springs, swapping rear ends is pretty easy, and can be done at any time in the future without affecting the rest of the car.

P.S.

I put a, AGR 12-1 close ratio steering box on mine. Now, its WAY to responsive, to an annoyance on straight roads, but an animal on mountain roads. Get the 14-1 variable...

I just purchased a Strange Dana 60. Some say it's overkill and it's a litttle on the heavy side but with over 400 to the wheels and probably another 150 shot of nitrous I'll take the added weight for the added strength. Plus it was $400 cheaper than the 12 bolt and 9".

12 bolt = 30 spline axles
9" = 31 spline axles
Dana 60 = 35 spline axles

It seemed like the right choice for me, I have had bad luck with exploding rear diffs.

I used an 8.5 inch ten bolt out of a 76 Camaro with a posi. They are easy to find and reletively cheap. The 76 Camaro/TA rear end is 1 inch wider so you have to be aware of that, but the rear end itself is plenty strong enough. 12 bolts are very expensive and are overkill in most street applications in my experience.

Dynawolf,

It depends on the engine & trans you plan on putting in it. If you go with a pretty much stock 307, 327 or 350 with around 300 HP or less the 10 bolt should be ok. If you go with a 350 with some high end horspower, big cam, head work, etc. and a trans that can withstand big HP then go with a stock 12 bolt. If you are looking to but a massive big block in it with serious horsepower and torque I would go with the Moser 12 bolt and get the T/A cover they make for it.

For what it's worth I have big plans for my 1969 down the road. I went with the Moser, the special cover and The Detroit True Trac. Before I did this alot of guys told me that would be the best set up for the street. The car originally had a spool. The previuos 1969 I owned has a 396 in it with close to 500 HP, a THM 400 built to death and a stall. That 12 bolt was stock and it held up great. Remember the stock 12 bolts were made to handle the legendary ZL1 and other 427's like the Baldwin Motion Phase III. In 1970 Motion transformed a 396 Camaro into one with a killer 454 and they had a stock 12 bolt in it.


Bottom Line: It depends on the engine & trans you are looking to put in there and if you plan to launch hard. If not then save some money and go with the 10 bolt. Stock 12 bolts are now around 2 grand. Yikes!!

P.S.

I put a, AGR 12-1 close ratio steering box on mine. Now, its WAY to responsive, to an annoyance on straight roads, but an animal on mountain roads. Get the 14-1 variable...

I found that a 15" steering wheel really helps tame the 12-1 ratio box in my car. Much better than the go-cart-like 13" wheel I was running before.



Dynowolf,

Whichever rear end you get, I highly recommend bolt-in axles. I broke an axle in my 67 Firebird with the 8.2 BOP rear (bolt-in axles) and the car just came to a nice smooth stop. A local 67 Camaro snapped his axle on the street and it trashed the quarter panel on its way out. :(

A properly set up 8.5" 10 bolt is just about as strong as the 12 bolt and a lot less expensive. I have a friend with a 65 Impala that runs 10.2 quarter mile times with a 10 bolt. A set of Moser axles will help substantially because the stock one are weak.

Thanks for the thoughts.

To be clear. I have a 12-bolt w/3.73 gearing. Former owner raced the car. It has a 350 with stock internals. I have switched out the powerglide for a th2004r already. I bought the car for the sheet metal - not a street racer.

Looking to trade for an open diff plus cash to buy a disk brake kit.

thx