I have a 1994 Camaro Z28 automatic, and according to my RPO code I have ''GU5'' which of course is 3.23's

However I just recently noticed my rpms don't match up,
@ cruising (45 mph) I do around 1500 RPM
@highway(75 mph) I do 2500 rpm, if not slightly higher

SO, if I am not mistaken I in fact have 3.73 gears, right?
SOOOO my question is what are the benefits of 3.73's over 3.23s? Cons? Ways to get the most out of it?

 

Sounds like you have 3.23 to me. Your transmission is only a 4 speed, and only 4th gear is an overdrive. Make sure you are putting the car into overdrive rather than drive when going along. But it sounds like your RPM's match the 3.23 to me, considering you are a 4 spd.

Benefits of 3.73's is increased acceleration and torque at the cost of less top end (though in street use its negligible).

 

transmission may not be locking up in od. you should feel 4 shifts and a lockup. its sorta like a half a shift. you could jack up the rear and jack stand it so it is sure not to fall. block the front wheels and put it in nutural. turn the wheel and make sure both wheels are turning and turning in the same direction, this confirms posi and its working, then turn the tire/wheel one revolution while counting the times the driveshaft turns. if it turns about 3 and 1/4 turns or 3.25 then you have 3.23 to 1 gears. if it turns about 3 and 3/4 times or 3.75 then its 3.73 to 1.

 

oh, alright. I've been reading on other forums that at those rpms are 3.73s so I was curious. How about my tire size? Does that affect my gears?

 

yes but will not have major effect unless theres a big difference in tire hight. i have 370s and am at about 60 at 2k rpms.

 

With factory size tires (245/50R16), 3.73 gears would put you at 2700 rpm @ 75 mph, in 4th gear.
3.55 gears would put you a hair over 2500 rpm.
3.23 gears would put you at 2300 rpm.

 

Your tire size will have no effect on your gears or your speedometer reading. It will effect how fast your car is going. Remember all the computer knows is how fast the tail shaft is spinning. You can change the gears and tires size and your computer has no idea your going faster or slower. If someone swapped gears they would have had to flash the PCM with the new gear info. There is nothing that would stop me from flashing my PCM to say I have 411s it would dispay RPM and MPH like I had 411s.

Normal tire wear and manufacture variation of tires can account for a about 3 MPH change in the speed of your car but your gage is only reporting how fast the output shaft is turning so no change is shown.

The point I am trying to make is the only way to be sure what gears you have is jack up the car and count revs of the tires it takes to make the drive shaft turn 10 times.

 

Thanks for the info guys. Ill be on the highway today to class, so ill be sure to keep a close eye on the rpms. But Ill do the old fashion method was I get my car on a lift so i can figure out what i reallly have.

 

If someone did change your gears mind you, and didn't recalibrate your speedo, you would need to have someone pace you in another car to tell you your correct speed.
My numbers above show what the car speed to engine rpm would be, but not necessarily what your speedo is reading.

 

i think he just called you guys old... lol. at 60 on the speedo time yourself for 60 sec. should go 1 mile on the odometer