Alright, when i bought my car it had old smaller tires on it, so i got new 245/50/16 tires...stock kind...so neways i was driving down the highway w/ the cruise set at 64 to be safe (60 is legal). For some reason it seemed like i was passing people alot but i thought nothing of it since they just bumped the speed up from 55 to 60 and just figured people hadn't realized it yet. Then i get pulled over and the cop was a real dick. I had a couple friends w/ me and he took all there licenses and told me i was going 68. I told him i had my cruise set at 64 and he gave me the whole speech about the speed limit is 60 not 64. So neways he let me off since it was my first time ever being pulled over. But the thing is, i haven't done ne mods to my car. so the gears should be the same and everything. is there a way to tell if the previous owner has changed them or not. like if i give you the rpm at 60mph...thanks for your time, Brady

 

Its possible the speedo drive gear in the transmission tail shaft was changed when the small tires were installed.

I'm not sure what color/teeth number are used with 245/50/16 tires and the rear end ratio in your car but your local dealer may be able to help you.

Its an easy swap. There is one bolt and a bracket that holds the gear assembly inside the transmission.

 

People NEVER EVER change the speedo gears when they downgrade the tires. If they really gave a rip about the car, htey wouldn't be downgrading the tires in the first place.

Like all the people on the Drivetrain board wanting to "calculate" their gears, I'd strongly suggest that you take your rear end cover off and check what gears you have. Far more likely than somebody dinking with your speedo gears, is that your car came with some one of the higher rear gear ratios, somebody tore it up, and they went to the junkyard and got what they could to replace it; which almost invariably would have a lower number gear.

You need to know what gears you have before you can even get the right speedo gears. Step one in any of this, is to find out for certain what gear you actuallt have: no guessing, no "my tach says x and my tires are y", no RPO codes, nothing EXCEPT take off the cover and look.

 

alright....so when i take the cover off.....what am i looking for to tell me the ratio..is the # written there or what....thanks for the help guys

 

Might seem like sort of a funny question, but actually, alot of times it is; somewhere on the edge of the ring gear, it's usually marked. Will look something like "41:11"; which would be 3.73 (41 / 11 = 3.727272727272....)

If it's not, or you can't find it, just count the teeth. For 3.73s, there'd be 41 on the ring, and 11 on the pinion. 3.42 is 41:12, 2.73 is 41:15, 3.08 is 40:13, 3.23 is 42:13, and so on.

Obviously only certain ratios are possible, since you can only have whole numbers of teeth. Well, in a working rear, anyway. I've seen a few with fractional teeth.... they were generally not what I'd call road-ready any more.

 

my 85 iroc is off on the speedo and everything is stock, and the rear has the 3.73's like stock

the speedo reads between 8 to 10 percent slower then what im going

ive clocked it with my moms new van, and my buddys new ranger, both bone stock

and the cop clocked me faster then it said i was going

 

hmmm, i didn't know any camaros even came w/ 3:73's. I'm prolly not gonna be checking ne time soon now...The average temp. this week has got to be in the single digits. Thanks for all the help.....

 

your car probably came with 215/75/R15 tires

like 90% of the thirdgen's did

check your door sticker... even then, it might have had a different door put on (hella common in these cars, so many different door problems)

check the backspacing on your rims

the cars that came with 245's stock had a different backspacing for the rear than they did for the front.

215 cars had the same rims all around.

 

my bad, didn't see that you had 16 inch rims, so I guess checking the rims won't work since they were swapped too more than likely (although because of your year and car, they probably ARE stock)

but i would check the RPO codes anyways... sounds like your car is supposed to have 15 inch rims on it with 215/75 tires.

 

nope, there different.....i can't change the back tires to the front soo i'm prety sure i've got everything right....it's not a big deal since i know about it now but iwas just wondering thanks

 

Yup, ALL the L69/5-speed cars came with 3.73s, and at least some of the L69/auto ones.

You'll find, if you measure, that the 245/50-16 is actually slightly smaller diameter than the 215/65-15 that so many of these came with. Not much difference though.... like 1/4" or so in most brands. So that change won't materially affect the speedo reading.

I don't believe I've ever seen one of these with 215/75-15 from the factory. That would look kind of .... weird.

 

sorry about that, i meant 215/65's. I was just going by memory, was a little hazy.

i mention this because i had the bigger setup on my rear recently, and my speedo was almost exactly 5 mph off at 65 to 70 mph. just like him.

that sounds pretty coincidental to me

my brothers 85 firebird had the 245 setup when he bought it and his speedo was off too. he put the 215's on it and it fixed it, it WILL make a difference. he did this because it was quicker and easier to get the 15 inch rims with tires used for cheap, so he doesn't have to swap his speedo gear yet AGAIN when he puts 18's on his car (he wants more sidewall with the 18's though) later.

and the back of my car sat QUITE A BIT higher with his tires on it. Extremely noticeable, the 16 inch tire combo is definitely taller. and a 1/4 inch of rubber around the circumfrence of a tire is quite a bit more running room for a full rotation.

I just put my regular rims and tires back on last week, and the car now sits level again.

bolinger - i'd check my RPO codes, and look for the 16 inch rim option... If its not there, then you have your problem. if so, i'd stick with the 16 inch wheels, and swap the speedo gear. but i'd also get a steering brace if i didn't have one. the frame can be prone to cracking behind the steering box with bigger tires.

i would in no way believe that someone changed the speedo gear in a car for smaller tires, and then later put the bigger tires back on... they just wouldn't do it. maybe for LARGER tires, yes. because there is an improvement and a logical reason.