so i apparently have a problem, i was recently at a tire shop getting my tire replaced when talking to the guy at the counter, i was told that there was something wrong with my car for doing 3200rpm at 70 in overdrive. this is my first car so i just kinda assumed it was normal. i don't really want to mess around with the rear end (because i have a habit of breaking things). i ran it through a couple rear gear simulators and it keeps coming up with really high numbers, like 4.56 to 4.84 range. anyone have any clue whats going on?

 

Bad gauge/Bad sender/Or swapped gears (least likely because you would KNOW it in the seat if you had gears that steep).

 

Jack up the rear end.
Put it on jackstands.
Put the tranny in Neutral.
Rotate the Passenger Side rear tire by hand 1 revolution while watching the pinion (where the driveshaft connects to the rear end) & count how many times the pinion yoke rotates.

 

90-92 tachs suck. They are notoriously incorrect. i believe there is a post that tells you how to fix it.

 

i did the rotate the pinion thing, and it rotated about 1 1/3 times.... the speedometer is just about even with my gps, so i know that's not wrong... and i don't think the tachometer is wrong because i have to push fairly hard on the pedal at 70, and the thing sounds like its getting a serious workout every time I'm on the highway, and i only get about 20 mpg at 70 and 22 at 65mph, which from looking around on this sight seems kinda low

 

so i guess my question is if there is any way the transmission/torque converter could be causing this, or is it more likely the rear gears? (which im really doubting because the last owner was a lawyer who did absolutely nothing to it at all)

 

You did something wrong or didn't explain your results right.

How many times did the pinion rotate for 1 full tire revolution? At a minimum you will find 2 3/4 turns. Cannot be anything less. Not possible. 2 3/4 turns gives you a 2.73 10-bolt/2.77 9-bolt.

 

Pretty sure you wouldn't get that kind of gas mileage if you were truly turning 3200. Sounds more like tach is reading wrong.

 

If you don't have a positraction rearend, and both wheels are off of the ground, the wheel opposite of the one you are turning whilst watching the driveshaft yoke spin is also turning the same amount (roughly) in the opposite direction (unless something is holding it still). So you have to multiply your (one side) tire's rotation by 2 to get the actual ratio.

Sounds like you might have about a 2:73 to 1.

 

Tach is off.

 

well, i compared the rpms my car said it was making to a tbi 305 truck, and it seems that my car idling at 1500rpm is off lol, i guess i just needed something to compare it to.... thanks to everyone who answered, and to those people who suggested the tach