quickslick86

I bought my Iroc with new gear's in the rear.

I don't know how low, but they are sure enough low ENOUGH.

So low that in first that lil ole 305 picks up the front wheels a few inches of the ground, and carries it.

Any Idea's on how to find out besides ripping into the rear end?


Thanks, Frank

Black6SpdTA

Jack the rear of the car up. Mark both the tires and the driveshaft. Have someone spin the tires ONE full rotation while you're under the car counting how many times the driveshaft goes around. You'll have to approximate though (i.e. 3 rotations = 3.08, little bit more than 4 = 4.10/11).
-Rippin

82355

Gonna call bluff on carrying the tires. It will probably raise the front of the car hard, but your not carrying the tires. You don't need to tare into the rear, just take the inspection cover off, clean everything off with brake cleaner and find the numbers on the ring gear. For example if they say 13 42 it means there are 13 teeth on the pinion and 42 on the ring gear, which equates to 3.23's.

Martin

Damon

Making sure that both rear tires spin the same amount as you count driveshaft revolutions is tough to do. Often times when you spin one wheel the other one spins the opposite direction and the driveshaft doesn't move (depending on what type of posi is in there).

Here's another way, similar in many respects but you don't have to deal with that issue:

Jack up ONE rear wheel and put the car in Neutral. Mark the tire and driveshaft as above. Rotate the tire 10 times exactly while counting driveshaft revolutions (and fractions to your best estimation). Multiply the result by 2 and then divide by 10. Bingo- your rear axle ratio. It'll never be dead-on exact due to slop in the gears and inaccuracies counting fractions of a driveshaft rev but it'll get you plenty close. The math of this is EXACT, not an estimation, but the slight inaccuracies will throw the result off slightly.

Marc 85Z28

How about the easiest way? Jack up both sides of the car with the trans in neutral and spin the DRIVESHAFT 1 full turn. Count wheel revolutions. The revolutions the tires spin is the ratio.

Ski89Z28

I got an easier way!
Go on the highway, leave the tranny in "D" NOT "OD" and take the car up to 74mph and look at the rpms and record that number.
RPM(recorded) / 1000 = gears

Example: 2770 / 1000 =2.77

Now this is assuming a few things.
1.) RPM gauge works and is fairly calibrated correctly.
2.) The tranny gear for the speed cable is the correct/matched gear for the rear.
3.) you have a 700 tranny cause the gear ratio for "D" is 1:1 don't know about manuals.

Else the way above is the best and most reliable IMHO.

Damon

.............. AND you have to have 26" tires. Tire size will throw off the RPM/MPH calculation as will many other things like the torque converter not locking up and the tach and speedo being off (3rd gen gagues are not the most accurate).

TheGreatJ

How about that way doesn't work? Try it....if you turn the driveshaft one revolution your tires are gonna turn like 1/4-1/3 of a revolution (depending on gearing.)

The best way to do it is to just pull the cover and get the number off the ring gear. It's 100% perfectly accurate and with an older car it probably needs the diff fluid changed anyway. Also since you just bought the car and the gears have obviously been changed you should look at the wear pattern to make sure it's set up correctly and isn't going to chew the teeth off in a couple thousand miles.