Did the oil change & changed the oil return pipe that was pinched,

Hit the button, and she fired right up, Wow what smoke!

Did the formula of rotating the rear tire 5 times and counting the pinion revs.
then divide by 10
Got 16 5/8 revs of the pinion/10 =1.6625.
Does this mean 6.62 gear ratio?

Thanks

Ron

 

wrong calculation, that would be 16 5/8 divided by 5 or 16.625/5 = 3.325

sounds like a 3.27, which is 16.4/5

so the trick is to increase the wheel turns to eliminate the partial turn of the driveshaft

if you had turned the wheel 50 times you would have had 165, almost 166 turns, or 164 turns. 164/50 = 3.27

this is an established ratio, 3.08, 3.27, 3.55, 3.73, 4.11

Sam

 

What I do, is jack one tire up, mark it, then mark the driveshaft. Now one person turns the one rear tire 20 times, and the other person counts the driveshaft rotations. Then divide the resulting turns of the driveshaft by 10. If you count 35, then you have 3.50 gears..

Doing it this way will let you tell the difference between 3.00, and 3.10 gears.

This method works great. If your truck is an F-5, they did come with a 6.6 ratio.

 

It is an F-5.
so the 3's ratio doesn't seem correct.

Should I re-do the tire spin? I did mark the pinion and tire. It came out 5 tire rotations, 16 and about 5/8 pinion rotations

 

Reamer

Devide the number of turns of the drive shaft by 1/2 the turns of the wheel.

16.625/2.5=6.65

Bob G

 

Hold on a sec, guys, ya got me confused.

1. Dueller mentioned one of the original F-5 rear end ratios is 6.66, and that matches the numbers in the parts book. Other options were apparently 5.83 and 5.14.
2. Ron, did you jack up only one side of the truck rear?

The formula is: Axle Ratio = (Pinion Revolutions) / (Wheel Revolutions X 2)

You can use any number of wheel revolutions you want - more revolutions will generally give you a more accurate axle ratio.

Examples:

You jack up only one side of the rear axle, turn the free wheel five complete revolutions, and get 66.6 complete pinion revolutions.

(66.6) / (5 x 2) = 6.66 Axle Ratio

You jack up only one side of the rear axle, turn the free wheel ten complete revolutions, and get .

(102.8) / (10 x 2) = 5.14 Axle Ratio

Have fun counting!

 

Getting more confused.
This is an F-5.
Jacked up one side, Rotated the tire five times.
The pinion rotated 16 and 5/8 total times.

16.625/ (5x2)

16.625 / 10 = 1.6625.

What do you get from this?

 

Yes, Sorry, I was using the posi calc instead of the open diff calc.

On open diff it is axle rotations / (wheel rotations/2)

so 16.625/ (5/2) = 6.65

Sam

 

thanks guys

 

Dang Ron, I screwed you up. Sorry man. I got a times 2 instead of a divide by 2. Thanks for the catch Sam.

As Same said, the formula is:

Axle Ratio = (Pinion Revolutions) / (Wheel Revolutions / 2)

 

Don't worry about it guys. we ironed it uot together!

Man, that was great dirving it down the road, grinding gears "like the good old days"!