I have an '81 Z/28 with what I assume is an 8.5 10 bolt. I'm building a mild 383 stroker that should produce near 400 hp and 440 pounds of torque naturally aspirated. We plan to use either a 700R4 or 200-4R transmission. I'm looking at somewhere between 3.73 and 4.11 for gears.

Originally I was planning to go to a Ford 9" but my builders price has doubled since I talked with him last fall. So now I'm wondering if I can get away with the rearend that's in the car.

What's available for parts to maybe make the existing rearend a little more abuse tolerant? Or should I see what's around for 12 bolts? Or just bite the bullet and go for the 9" even though it's gonna add another three or four months to the project? :confused:

Thanks!

I would go with a 3.42 gear ratio. You can build that 10 bolt up pretty good. I would think it would handle 400 hp anyway.

You can put in a 30 spline Eaton posi and a set of 30 spline Moser axles. This will bring the strength up near to the 12 bolt. A 3.73 would probably be the best choice with the very low first gear in the 700R4. If you need more information on these parts send me an email. gears@muhlon.com

Eaton 19559?

Should I stick with the standard 400# or go to 800# & steel clutches?

Thanks!

If you will be drag racing more than driving it on the street then go with the 800 pound springs and steel clutches. If this is a street car then stick with the 400 pound springs and stock clutches. Let me know if you need prices.

BGH, I've been reading a few posts from the previous years and it sounds like you know your gearing. I'm not planning on making a strip car out of my 68, but an occasional trip to the strip would be fun. How can I tell if I have the 8.2 or the 8.5 10 bolt rear end? And I can build it up a bit by changing the axles and putting an Eaton posi in it... chicks dig Eatons, or so I've read!! I have a Muncie with the 2.20 1st gear ratio. So the 3.76 would be the better option for the diff? I'm planning on going up to Hot August Nights in Reno and hopefully I can find some good deals on some of these parts. Thanks for the help. The motor is a 350 crate. I have no idea how much hp or torque.

Robert

The 3.73 will wind the engine up a lot at highway speeds, but if you only plan on driving it around town then it would be all right. If it is an '81 then it should have the 8.5. The 8.2 was not used in a Camaro after '70. If you want to be sure then you can check the pinion nut. If it is 1 1/8 it is an 8.2 and if it is 1 1/4 it is an 8.5. The 8.5 also has some square corners at the bottom of the housing. If you want me to give you prices on these parts send me an email.

Thanks, email enroute.

Robert

I would go with the 3.73 before the 4.11. I have 4.11 in my car and it's great...until I hit 80 :p I bought the car that way, but if I ever change my rear brakes I'll probably swap it out to a 3:73 something a little more all-around.

I bought my gears and posi from Freddie, good to deal with too.

I put in 3.73's and have 27.5" tall tires now but were 26" tall before. At 65ish with the 26"s rpm's were 3300ish and now with the 27.5's its about 3000 rpm. Hope this helps you out.

What's the right rearend? The one whose sole purpose is complimenting the car, ie., Jennifer Anniston, Stevie Nicks, Courtney Cox, Gwen Paltrow, J Lo, and others........