hi guys, im new to this board and am interested in bringing back the old third gen. so on my quest, i was in search to make my engine breathe better. i bought some knN air filters. then to get a catback. however i saw that my car had a nice tone and a pretty meaty I-pipe, well it turned out to be flowmaster cat back. i bought the car for a dealership and they said the guy who sold it to em was a real gear head. so, now im in search for gears. but how do i know i dont already have nice ones? my axle code is 2HT meaning its a 2.73 posi rear end, but how can you tell if a gearhead before changed em out. is they a way to tell my what speed your at vs the rpm? while crusin on the freeway, im at 80mph and at about 3500 rpm in my last gear.(auto). does that matter or it has nothing to do with gear ratio? what rpm are you auto guys at with higher/lower gears at 80 mph? thanks alot.
ps. not too comfortable with removing cover just yet.

 

Well, raise the rear of the car so both tires are just off of the ground and put the trans in "N". Rotate the RR wheel and if both wheels turn in the same direction you have a limited slip rearend. To check the gear ratio make a chalk mark on the tire and one on the floor so they line up. Now make a chalk mark length wise on the drive shaft. Rotate the tire one compleat turn and count the number of times the driveshaft rotates. Example: Driveshaft rotates 3.5 times to one rotation of the tire = 3.50 gears.

Auggie

 

put it in 3rd gear (3spd or 4spd auto) and check the RPM @ 70mph. If you have close to a 26" tire. Example: with 3.73 rear gears and a stock height 235/60R15 tyre, you should be turning approximately 3730 rpm. My guess is you have 4.10 gears.

 

wow you think i have 4.1 gears? its an 87 z28 with the iroc pkg, and it has the stock iroc rims. 4.1 may be a little bit too much gear, but its alot better than the mighty 2.73

 

Um your tach is way off or your torque converter isn't locking up, or both.

.7 overdrive , 13.25" tire radius, 3500 rpm, and 77 mph means that something is fubar or you have 5.13 gears

Does your car have overdrive?

 

yea it has overdrive. maybe the tach is way off. the gear head who had my car before i got it supposily but in a L98 engine. i called the BS on the dealership but i just wanted a 3rd gen in good condition. however the engine does look nice, but im almost sure its a LB9. looks like new, with the fresh chevy engine red paint. but could a rebuild screw up the tach? when i floor it, the engine will rev to 7000 rpms before it upshifts. now i know thats not too smart, but if the tranny lets me do it, then it should be okay, or like you said, the tach is off. please reply back. thanks.

 

Definately your tach is off. Fix that first. Should shift at 4500 - 5000 rpm at WOT. Good luck.