Ok I was my local junkyard looking around and came across to 6 cyl thirdgens, a Camaro and a Firebird S/E. I ran the vins and came up with the firebird having a 3.23 and the Camaro having a 3.42. Now according to a site the 3.42 is an open rear end? Is this correct? I am going back tommorow to check physically by doing the turn the wheel test. Also does anyone know if the Firebird's 3.23 is a posi or open? I am currently running a 2.73 open rear end so any of this will be a big improvement haha. Also with prob right under 200hp do I need a posi traction? Will I see any gain with a posi traction rear end, or is this just for show? Any opinion will be appreciated, I am running a 89 Formula with a 305TBI w/ Open element and K&N filter. Let me know what yall think. If all else fails Ill drive down to thirdgen and pick up a 3.73 posi haha

A posi is always an improvement over an open rear. The traction gained is significant.

An open rear with a higher gear ratio will just bake your right rear tire even worse than it does now.

As to whether or not the rears are posi the only thing you can do is test, or pull the cover. So much can be changed since the cars were new that there is no real way to tell just from RPOs.

So from a standing start with an automatic and 200hp, would a 3.42 open or a 3.23 posi win in a race?

TKO is right about the addition of posi being nice. However, upgrading to a 3.42 ratio, even if it's a one-legger, is a huge seat of the pants improvement over crappy 2.73's. I switched from 2.73 to a 3.42 open rear and loved the increase in take off power. I ended up putting in a 3.23 rear because it had posi and rear disc, which is very nice. I just wish I still had the 3.42 ratio along with the posi and discs!

If both cars were perfectly equal motor wise, it would depend on driver skill. If the guy with the open 3.42 rear could get the car to hook up without too much wheelspin, which is the advantage of a posi, he would win in a quarter mile race.

Heres another point of this, I am going to a very good deal on this rear hopefully around 100.00 so for 100.00 is a 3.42 (even if its open) not a great upgrade for my 2.73 Formula? And since its so cheap I can afford to get a TransGo Shift Kit also But the question is if the 3.23 is posi should I get it or the 3.42 open?

If the 3.23 is indeed a posi and the posi still works good, and it's the same price for either rear, I'd probably go with the 3.23 rear. There's not a huge difference between the two ratios.

How much more do you think the 3.23 is worth than the 3.42 open?

Errr I just answered my question, in 84 the G92 option was not avaliable which means both rear ends are open. Now should I get the 3.42 for say 100.00 or go up to ThirdGen Resource and spend probally around 300 and get a posi? Let me know opinions.

Posi rears were available in 84 regardless of whether there was a G92 option available or not. The RPO # for posi is G80. The easiest way to tell for sure is obvious. Either remove the back cover on the rear and look at the carrier or turn one of the axles and see if the other axle spins the same direction or the opposite direction. If it spins the same direction, it's a posi. If it spins the opposite direction, it's either an open rear or a shot posi.

ok thanx, my friend must have gotten the years mixed up when he told me that.

You should check out a couple things when buying a used rear that I forgot to mention.

If it's a posi make sure that it works.

Pull an axel and check the bearing surface. If it's all galled and wasted you will need a set of axels. Also, count the splines. 26 spline units are okay, but 28s are better.

Check the slop in the pinion yoke. If the gears clunk around and the yoke has a lot of play in it the rear is probably junk. Also, inspect the gears for cracks, broken teeth, and abnormal wear.

Just make sure that it is a good deal. Paying $100 for a rear that needs hundreds to get it in good working order again is a waste of money, because you could just rebuild your rear with better gears and a posi for the same price.

BTW, if the posi is good I'd go with the 3.23s.

Thanks for the info