Today i finally decided to check on my own as to what rear end gears i have. I thought that i had an 8 in rear with 2.79's because the data plate on the door and on the rear end said so, but that doesnt seem to be the case. I marked a spot on the drive shaft and on the wheel, jacked the car up off the ground and put her into neutral, then i rotated the wheel one full turn while my brother watched to see how many times the drive shaft spun, ithe shaft only spun about 1. 40 times. I thought that must be a mistake so i tried it again but this time we switched spots and i watched the drive shaft, sure enough about 1.40 times. I then decided to conduct the test on my fathers 69 cougar and for one rotation of the wheel the drive shaft rotated 3.25 times, which made perfect sense.
What do you all think of this, i knew it had high gears like 2.79's but not 1.40 high.
also the number stamped on the pumpkin reads: C60WA AE18 Doesnt C6 mean 1966?
I am confused!
Matt

 

have you got an open diff? (ie single spinner)

i may be way off track, but if you have, and both wheels are off the ground, maybe the other wheel turning the other way is giving you a false idea????

if it was 1.40 it would take about a week to do the quarter mile but have a top speed of 400mph if you had the power!!!

 

Yeah, it is an open diff, and both wheels were off the ground. i didnt pay any attention to the other wheel moving at all, so that wasnt a distraction. The car runs and drives fine, no weird noises from the rear. Should i try and lock the other wheel up with a block, and try the test again? I have never even heard of gears less then like 2.50's, it just doesnt make sense to have 1.40's!
matt

 

yes, just a block or lower that side to the ground or just hold it by hand...curious to see if that is it.

1.4 x 2 = 2.8 or near enough to 2.79...coincidence or not??

 

Yes, C6 means 1966. You have 2.78's on there. Ford (or anybody else for that matter) didn't ever make a 1.40. You could not get the car moving in 1st gear.

 

yes, C6 means 1966. MY best guess is gonna be along the line of Aussie's. Make sure both wheels spin together at the same rate. Or try to spin the driveshaft with some man muscle and some grip-gloves and then see how may turns of the shaft you need to get the tire around. Good luck.


P.S. Upon some further investigation, it is possible you have the code slightly off and that you have a 7.25in rear with a 2.83:1 integral diff. My code book only knows so much..and that was just a shot in the dark

 

Maybe, that is a good spot, ill test it out and get back to you in a little bit.
Matt

 

This was discussed on another thread a while back and I posted the correct way to find the ratio, although several people thought this was incorrect. https://mustangforums.com/m_1863896/tm.htm

 

Try turning the DRIVESHAFT as opposed to the wheel. The wheels turning opposite directions and the gear ratios inside the differential make a difference.

If its a locking rear you can turn either one, but an open rear you need to move the driveshaft with the wheels free...

 

so...1.4 x 2 = 2.8 or near enough to 2.79... Is that what you meant??