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View Full Version : 8.5 10 bolt or 12 bolt



justasquid
07-17-2010, 07:09 PM
Ok, I know many of you have been helping me a ton here in regards to my future build of my 68 camaro, and I really appreciate it. I originally thought I had the weaker 10 bolt in my car, but it turns out, I actually have the stronger 8.5 10 bolt. I have gotten great advice so far on the possible 12 bolt I may run,
But, my questions is, will the 8.5 rear hold up well to 450 crank hp? It will be an ls-1 with a 6 speed, and I'm leaning towards 410 gears, if that makes any difference. I was wanting to go stronger, in case I decided to upgrade power later on, but honestly, 450hp will probably be my limit for quite some time.

If the 10 bolt will be strong enough, do I have to upgrade anything, such as axles or anything? and if so, does anyone have any suggestions on what brand to use? I think its a non limited slip, so I will more than likely be upgrading it to a limited slip. would a moser 30 spline be the way to go?

thanks again everyone. I'm trying to stay within a budget, but not at the cost of broken parts.

also, the car will see mostly daily driving.

LSXfan
07-18-2010, 04:56 AM
i think your current rear will be more than adequate for the power you have planned....to put it in perspective the ring gear for the big 10 bolt is 8.5", the 12 bolt ring gear size is 8.875 "......not worth the change IMO

big gear head
07-18-2010, 01:22 PM
I've built many 8.5 rear ends for early Camaros and Novas. Here is what I recommend for your application. I would use a new 30 spline Eaton Posi, 30 spline Moser axles and Timken bearings. I usually use Yukon gears, but there are other good gears out there. The reason that I use Moser axles is becasue they are the only company that makes the axles just for the 8.5 10 bolt. All of the other companies use a 12 bolt axle, which must be modified to fit the 8.5 10 bolt. With high powered cars and cars that will run slicks I also fuly weld the axle tubes with nickel and I brace the spring perches. Welding the axle tubes is a little more important with the 8.5 because the factory plug welds are usually pretty poor quality.

The price list usually goes about like this. Eaton Posi $415, Moser axles $235, Yukon gears $165, installation kit $96, axle bearings and seals $30, axle studs $25, welding the axle tubes $100, bracing the spring perches $40, assembly labor $200. That will give you an idea of the cost of building the 8.5 so you can compare that to the cost of a 12 bolt. A similar Moser 12 bolt usually goes for around $1910 and up, depending on the options that you pick.

justasquid
07-18-2010, 01:28 PM
not worth the change IMO

Thanks for the reassurance. Thats what I was hoping for.

Is there a need to upgrade axles or any other internals?

GM Muscle
07-18-2010, 02:49 PM
id just build your 10bolt and roll on..

LSXfan
07-18-2010, 04:03 PM
Thanks for the reassurance. Thats what I was hoping for.

Is there a need to upgrade axles or any other internals?

I wouldnt worry about that either even with an occasional track visit

big gear head
07-18-2010, 05:41 PM
If you have a standard differential in it now and you are going to upgrade it to a posi then go ahead and get the 30 spline parts. Almost every one of these rear ends that I have disassembled had bad axles in them anyway. The money is the same for 28 and 30 spline parts.

Taman
07-18-2010, 05:49 PM
I ran a stock 10 bolt with the 8.5" gear. I had 475 rwhp at the time. Ran slicks at the track and it lasted several years. I sold it for what I paid for it. 12 bolt isn't necessary unless you plan on racing with slicks and clutch dumps and hp upgrades in the future.

justasquid
07-18-2010, 07:43 PM
Thanks for the in depth information BigGearHead. looks like I will be going with the 30 spline for sure. I didn't know that other companies require modifications, so that certainly could have been some extra cost I wasn't planning on.

The most abuse the rear end will see is probably some sticky street tires on an occasional road course. It may see some heavy clutch dumps, but again, on street tires. the rest of the time, it will be a sunny day ride, protours... mainly just having fun driving the car.

again, thanks everyone for taking the time to offer their input. It is greatly appreciated.