I have a 68 camaro with a 350 that has about 400 rear wheel horsepower. This is backed up by a TH350 with a shift kit, soon to be 3000-+ rpm stall converter and a tranny cooler. I'm going to be getting my 8.2 rear-end rebuilt very soon because I can get a great deal on an entire posi, gears, and bearing's package. The only thing is, I was planning on going with 3.55's but my only options are 3.42's or 3.73's. I want my car to do at least about 125 but I want to be able to run 12.99's. How big of a difference will I see? I'm going from an open 2.73 currently and I do about 70/30 street to highway cruising with the street being more.
Thanks alot,
Donnie

The 3.42 will be a great compromise, you won't lose that much time at the track and they are great on the highway. You should have no problem getting into the 12's with the 3.42's. I have run both gears on the street and I can tell you that the 3.73's are borderline on the street without overdrive. This will all also depend on how tall a tire you are running. If you are running a tall tire 28" or taller on the street then the 3.73's will be tolerable. With a 26" tall tire I say go with the 3.42's. If you have a 8.2" rear you should be able to get 3.55's and I would say that would be the optimum gear for street/strip. I know they don't make the 3.55 for an 8.5" but they do for an 8.2"

Royce

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70 Camaro 383ci
69 Camaro 385ci
2000 GMC Z71
Link to my 70

http://profiles.yahoo.com/camaroman7d

Thanks alot, and yeah I know that a 3.55 is available but the company that has the sale going on right now only sells 3.08, 3.42, 3.73, and 4.10's or at least that's what the add says. Oh, I'll be running either a 255-50-16 or a 275-50-16(if the 275's will fit) and I'll be running what ever is the largest front tire possible on the front with 16 inch rims if the fronts matter.
Thanks again,
Donnie

3.42's will be the way to go with those tires. I'm sure they will be in the 26" range.

Royce

Oh okay thanks alot,
Donnie

Use this to figure it out.

Mph = rpm x tire dia./rear gear ratio x 336.

3000 rpm x 26"/3.42 x 336 = 67.9 mph.
Or,
3000 x 28"/3.42 x 336 = 73.1
And;
3000 rpm x 28"/3.73 x 336 = 67.0 mph.
Or,
3000 x 26"/3.73 x 336 = 62.2mph. pdq67

Thanks alot pdq67 that's awesome! Do you or anyone else know about what my top speed will be with the 3.42's or with my current 2.73's? All I know is that it's faster than 120 right now because that's as high as the stock speedo goes.
Thanks again,
Donnie
P.S. Will posi-traction make my car any faster or slower top speed wise?

no, it makes your rear have better traction. maybe if your slipping a little at high speeds.

Camaronotcamaro- thanks alot, that's what I was thinking but I'm only 16 and I just wanted to be sure cause I haven't learned all that much about rear-ends yet.
Donnie

Sure, just plug in your max rpm into the equation above along with the tire dia. you settle on and disregard any slippage if you have an automatic. You won't be right on, but close!

I went from 70 to about 82 mgh at about 3050/3100rpm with my 3.31's when I ran my talll Snow tires years ago. pdq67

try this page out it will do the math for you
http://www.smokemup.com/utilities/calc/mph_range.cfm

Thanks pdq and c4boom, that formula is awesome but do you really think that my car will do 145+!? Right now the speedo only reads 120 so I don't know how fast it really is but it buries the speedo!
Thanks again guys,
Donnie

Find one of those speed signs check it out to see if it has a camera so you wont get nailed and run it or you can convert the rpm's to mph

Unless your Camaro's suspension is in better than off-the-showroom floor condition (modern tech springs, etc), I don't think it would be safe at that speed. Even if you do have a tight suspesion that won't start to wander at that speed, doing it on the street is asking for big trouble. See if you can take the car to a big circle track and get them to clock you in the straightaway if you must check.

ya that would suck if you got out of shape at that speed

Who makes 3.42s for an 8.2 ? I thought it was 3.55 for the 8.2 and 3.42 for the 8.5. Then again I'm still learning.

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Robert

'69 getting better every day... (every pay day)

I know this sounds dumb but what exactly do yall mean by 3.08, 3.42, 3.73, 4.10? I know it's a gear ratio, but what does that mean? Also, when someone says that they have a 9" rear end, does that mean that they shortened the axle by 9"? Thanks in advance.

the gear ratio is how many times the drive shaft has to turn for one turn of the tires a 3.00 to one means that the drive shaft has to turn 3 time to turn the tires one time a 9" is a ford developed axle with no differential cover a 9 " ring gear and a removable third section that holds the carrier

Rojo- I just have an add from a super chevy or CHP that says 3.42 for an 8.2. But, I would much rather have 3.55's if the deal apply's to those also because in my opinion(with no overdrive) that is the perfect street/strip gear.
Donnie

Donnie,

I'm still not sure. Maybe someone with a little more knowledge will jump in. I do know you can buy Richmond 3.55s for a 8.2 from Jegs for $189. I'm in the middle of rebuilding my 8.2 with 3.55s and the new Eaton posi. I was lucky enough to find a new gear set from an individual at a real good price. I then got a super deal on the posi and rebuild kit from "big gear head" that frequents this site. While I was looking around I just never did see a 3.42 for the 8.2, that doesn’t mean it isn't so.


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Robert

'69 getting better every day... (every pay day)

I have 3.55 posi in my 8.2. I have a 350 with a m-21 and really like it for freeway, at 70 mph, I'm around 3000 rpm, which is perfect because I can really rev it up and it's in good power range for passing and top speed.

lil beast- That's basically what everyone says, that a 3.55 is the "perfect" street/strip gear. Even though I have a TH350 I think that my cruise at about 65 would be close to 3000 rpm which is exactly what I'm looking for. Now I just have to find out if I can get a package deal on that ratio instead of the 3.42's.
Donnie

While we are talking about 8.2 and 8.5 I want to make my 1 legged 2.56 8.2 into posi 3.55. I have been told that I should get a 8.5 because it is stronger and cheaper to posi it. Any thoughts or suggestions? While we are at it, anyone know of a good gear and axle company in the DFW area?

Thanks
Kelly

[This message has been edited by kgb69 (edited 12-06-2001).]

KGB69- An 8.5 is stronger than an 8.2 and I'm probably pushing it with 400 rear wheel horsepower. How much power (what is your motor, tranny, and motor stats)? That's really what it depends on and also if you're going to be using it with slicks or on a strip alot.
Good luck,
Donnie