im still sittin on the stock rear end in my '82 firebird trans am 355. What would be the best gear ratio and size to go with when i replace the ring and pinion? what setups have worked best for you guys?

 

The size is 7.5"/7.625". Only one that will fit.

As far as the ratio, that would depend on the RPM power band of the motor, best determined by running it on a chassis dyno; and the intended use of the car. Together with the driver's tolerance for the downsides of any given choice.

I'm going to assume that the stuff in your profile is just random garbage, or applies to some other car; since 4.10s didn't come in any of these cars, and neither did a 4T60 (thank goodness... although I'm given to understand it was a near thing at one time).

What transmission do you REALLY have, and what gears?

 

when i bought the car and signed up on here i was told the rear end had 4.10s and that was actually the transmission the car had in it when i got it. since then it has gone out and i found a 700r4 that got thrown in. i want to say that the gears are at 3.73 but i cant be sure without tearin the rear end down...and its too cold for that

 

No, the car DID NOT have a 4T60 in it. "T" in the model # stands for "transverse", which is the designation for a front-wheel-drive transmission. Totally not possible (thank goodness) in one of these cars. The same series of designations (which they started using in about 90 or so) for a 700-4R is 4L60, in which "L" stands for "longitudinal", which is rear-wheel-drive.

Not that "what used to be in it" is a real big deal in and of itself; but it indicates that you are VERY confused about transmission models in general, and that nothing you think you know about transmissions is likely to be accurate. Not to be personal or anything, only, it shows you need some REAL information and education.

Go here and print the page. Then go out and get under your car and compare the pan to these, to identify your trans with certainty.

The only way to know what gears are in a rear end, with certainty, is to take off the cover and look. No "tearing down" is necessary. All you have to do, is change the fluid, like you should be doing ANYWAY; and make a point of looking at the gears while you're doing the basic "just got the car" maintenance. Most gear sets have the ratio stamped on the edge of the ring gear; like "41:11" which would be 3.73 (41 / 11 = 3.7272727272...), or "40:13" which would be 3.08, etc. If your gear doesn't have that, just count the teeth on the ring and divide by the teeth on the pinion. Make a point also of looking inside the little window of the carrier, and seeing if there's clutches and springs and things in there (basically, anything besides a shaft and 4 small gears), so we don't get yet another redundant "do I have posi" post.

Your 82 would have come with a 200C trans and probably 2.73, 2.93, or 3.08 gears, and most likely NOT a posi. Of course there's no guarantee that that's what's still there, which is why you need to look. There is NO SUBSTITUTE for doing the common-sense lubrication, and looking; and making excuses why it's "too hard" doesn't change that. Either you want to know, in which case you'll do what it takes; or you aren't willing to do what it takes, in which case you must not want to know very bad. Again, nothing personal, just facts.

 

like sofa said first figure out exactly what you have and decide what you want to do with the car. That being said if its a 700r4 your 4th gear is an overdrive so i would probably lean more towards 3.73 if the car is just a pleasure vehicle driven around town or on short trips and 3.42s if you spend most of your time on the highway

 

sofakingdom...look, i got the car less than two weeks ago and before that did work on it once when we put the new trans in. and up to this point i have been working on imports my whole life. what i have put on here is what i have been told...i don't have a garage and my house is surrounded by fields, so i haven't gotten a chance to get out and do anything with this piece o ****. so gimme a ****in break and just help me out...don't put me down. If thats all you want to do on here then id rather not have your advice. no offense...Just the facts.


WIII36....thanks that was actually exactly what i was looking for.

 

Same here.

People come on here non-stop, with all kinds of excuses about how they "can't" take the cover off their rear end and look in it. Doesn't matter how good the excuse is, or even, if it's REALLY true; the fact remains, it's the only way. You cannot believe, until you've dealt with it for a while, how annoying it is to tell people what needs to be done, and they come back with a bunch of "but... but.... but.... " as if somehow, the quality of the excuse makes the thing they need to do, just disappear. Trust me, it doesn't.

Again, I cannot stress this strongly enough; it's NOT PERSONAL, I'm not "attacking" you, I'm not "putting you down", or anything like that. It's just the way it is. Like I said, it takes what it takes, to get it done; either you want to know what's in your rear end, or what transmission you actually have, in which case you'll do what it takes, or you don't care enough to do what it takes. No amount of posting foul language on the Internet, or getting all bowed up about it, will change that. It is what it is.

What you've been told is obviously WRONG, and you lack the knowledge to identify that. That much is clear, since you were "told" your car had a FWD trans in it, and you believed it. Clearly, not possible (thank goodness). But that's OK, there's nothing wrong with not knowing something, when you're new to it. OTOH, if you don't know enough about transmission models to know the dfference, then don't get all worked up about what you think you "know" about this one when you discover it's wrong. It's OK not to "know". That's where we all start out. Don't close off your mind and get all offended just because it's been pointed out to you that what you think you "know" is completely wrong. For all I know, the seller might have been a con artist, and just pumping your butt full of sunshine to get you to pay extra, by telling you what he thought you wanted to hear; in which case, it's all lies, anyway. Most of what you hear from used-car sellers is just that.

Now, I've told what you need to do, given you a page with pictures on it that you can look at, and told you what to look for; it's not my problem if you don't want to know. Again, if you REALLY want to know, you'll quit making excuses, and do what it takes; if you don't REALLY want to know, then you won't. It's OK with me either way. Just don't attack ME for pointing out the obvious.

 

I went with 3.23s on my car and they are better than the 2.73s that were in it when I got the car, just think of where you drive the most (highway or street) and I'm sure someone can point you in the right direction.