BeastMachine67

is there any way of finding out what ratio your rear gears are without removing the pumpkin and counting the teeth?? some people say to just look at the tag on the axle but mine doesn't have one. any ideas?

68EFIvert

Jack the car up and turn the wheels. Mark the drive shaft and count the number or rotations of the drive shaft for one rotation of the wheel. Do it in neutral. If the drive shaft rotates 3.5 times for one wheel rotation you have a 3.50 gears.

BeastMachine67

turn both wheels?

1965screamer

It doesnt matter which tire just whatever tire is turning when you are turning the drive shaft

Norm Peterson

If you have an open diff, you have to double the driveshaft revolutions (and leave one rear tire on the ground so it won't turn in the opposite direction and throw your count all off). Here's one link from a Search on 'axle ratio'.

https://mustangforums.com/forum/clas...han-2-1-a.html



Norm

2+2GT

It is easiest if you turn both wheels the same way at the same time.

THUMPIN455

Quite true. Put the car on jack stands, get under it with the shifter in neutral, put a mark on the inside edge of a tire, then mark the driveshaft in a place you can count revolutions. Turn the driveshaft by hand and count how many times the mark goes around for one revolution of the wheel. 3 turns is 3.00 gears, not quite 3 is 2.79, a bit more than 4 turns is 4.10, and three and a half is 3.50. Quite simple and you dont have to worry about play in the spider gears doing it this way.

BeastMachine67

I tried it...how lame mine is about 2.50 lol! But I guess it makes sense since the car was a orginally 200ci 6cyl

THUMPIN455

Eh, I run 2.41, 2.56, and 2.73 gears in some of my 400 or 455 powered Trans Am/Formula birds, put enough grunt to it and you can move it along no problem. The best thing is they have low rpm on the highway, saves wear on the engine and cheaper on gas. Of course you spin much farther with more smoke with the highway gears provided you have power to spin them. The 70 GTO with a 2.93 posi rear would roast the 275 60 15s from 30 mph or smoke them for 1/8 mile just by whackin the throttle, no need to hold the brake to get them turning.

A bud of mine has a 99 Z28 that had 2.73 gears, only bolt ons like headers, stall under drive pulley and a lid, that thing ran 11.8 with those highway gears and an auto trans. No he wasnt spraying any nitrous to it, all motor and it was stock internally.

So the gears arent lame, but the power ahead of them might be..

BeastMachine67

Well it makes sense to me now though. I my old 69 had a 4spd toploader and I wasn't sure what the ratio of the rear gears were but I know it was 3 something. Anyways that thing moved!! Just the take off and torque alone was awsome! So with the 67 I have now, after I installed a late model 5.0 motor and a 5spd tranny to back it up, I was a lil disappointed at the performance. So I'm definately going to look into upgrading the gears one day. I just have to figure out more or less what ratio to go with.