at 65mph my rpm is like 2200 and i have a 3 spd..my cousin said that it must have tall highway gears and that takes away from getting going as fast..why would somebody do that? and should i change it? do rear gear ratios have anything to do with it?

 

If you have highway gears in it then you'll get better gas mileage and a higher top end speed but suck at launching off the line. With street gears you'll have good launch but horrible top end speeds without high RPM and more fuel consumption. Lower RPM at higher speeds = better gas mileage on highway.

 

ok thanks for clarifying kyphur ..also can you give me an example of a highway gear ratio and a street gear ratio? and on average, how much gas mileage would i lose on the highway if i switched to street gears?

 

Well, the person that had my car before me put 2.72 (or 2.52) gears in there from a 77 Camaro if I remember right. Usually street gears are lower (remember, lower gear means higher number) than 3.42 and up. You'll notice a significant drop in mpg going lower a full gear. Like if you went from a 2.72 to a 3.72. You also wouldn't get a lot of high speed out of the car unless you can get the engine to turn higher RPM to make up for the RPM you're losing with the lower gear from the higher gear. Your transmission also has a major play in this also with the type of gearing it has in it. If it has an OD you can go down in your gears by around 25% to 30% and still get the bonus of having a streetable gear in your lower transmission gears and then being able to have a hwy RPM to some degree. You'll still take a hit on gas mileage but it would be like not having the OD and having a 1 to 1 turn ratio with the tranny rather than a .70 to 1 ratio (depending on the OD gear).

Are you planning on only keeping this car as a strip vehicle or do you want to take it out on the highway? What type of driving are you going to be doing the most of? Highway? Racing? Weekends only around town?

 

well if i get like 15mpg now, how much do you think i'd be getting if i dropped a full gear? well i dont have an OD now but am thinking of getting one if i lowered the gears...well im using it as my daily driver and do alot of freeway driving but i also want to be able to be able to use it for street racing if i want too...

 

have you done any engine mods?

 

no i think the engines pretty much stock

 

are you sure that it's a 350 and not a 305? For 1981 I only see the LG-4 engine (305 CID) having a stick and having a 2.52:1 axel ratio. You also say it's a three speed which according to Nastyz28.com was only in the 6 cylinder Camaros.

 

well its an automatic not a manual. the engines been rebuilt but im pretty sure its a 350.

 

Ah, o.k. When I saw 3spd I thought manual. Sorry.

Well, back to your original question. I would work the engine up first and then the axle but that's just me. Especially if it's a daily driver that you put a lot of highway miles on. More miles, more and higher RPM's = wear and tear and more money on gas. If it was a weekend warrior or a racer I would suggest it then. If you've got money to blow on gas and parts then go right ahead. I know 70 bucks a tank for me is pretty harsh every week sometimes.

Using a speed calculator and going with stock tires of 225/60/15 (that's stock if I remember correctly) you should be hitting 58 at 2000 RPM's and 72 at 2500. Going to a 3.42 gear will give you 43 mph at 2000 and 53 at 2500... just to reach your current 2500 rpm speed of 72 mph you would need to be turning almost 1000 (3500) more rpm to reach 74 mph and 4000 just for 86.