HI all... Listen, I had my stock 3:55 gears swapped out for a new set of 4:56 gears due to past towing problems and the power loss from running 32x11.5x15 tires. My trucks a 94 F150 Flareside extended cab 4x2. It also has a 6"lift...

Anyway, The gear change was about 580 miles ago and I've yet to be impressed and/or atleast "happy" with the new performance.
So, I finally decided to jack up the 'ol rear end and mark the drive shaft and tire and spin the tire 1 revolution while counting the drive shaft revolutions. (the old way of checking a gear size)

I posted this in the tranny forum by accident, so my apologies to those that are offended by double posts...lol

Anyway, with the tire size i'm running, I figured with the 4:56 gears, the drive shaft should atleast turn 3.5 turns.....(if not 4 full turns)...

My shaft only turns 2.15 turns!! That tells me that the swap never happened, right? Cuz 3:55 gears with 32" tires, would be reduced to almost a 2:23 or so, right? It appears as though my stock 3:55 gears are still in their after I payed big bucks to have the gear change..
What do you all think?
If I have a different shop pull off the pumpkin, can they tell by looking at the gears just exactly what they really are?
I want some more solid proof before I go back to the original shop and make any accusations...
Help please....
The Drive shaft/Tire spin method is fairly accurate, is it not?
Thanks..

 

Doesn't matter what size your tires are, 1 revolution of your tire should spin the driveshaft 4.56 times.

If you have someone tear it down, just divide the number of teeth on the ring gear by the number of teeth on the pinion.

 

I think that you just measured inaccurately since there are no gears in that range. It doesn't matter what size tire. You could measure the axle, rim, or either tire and get the same reading. If you can't do this method, try the ring gear teeth divided by pinion teeth method.

 

Law;

Are you sure that your wheel on the other side of the axle was not spinning as well as the one that you were turning? If it was, there is no way of telling what the ratio is. If you have a posi-trac rear end and lift both rear tires off the ground, then one revolution of the tire will spin the driveshaft a number of turns equal to your gear ratio. If you don't have posi-trac and lift both tires off of the ground, one may spin opposite to the one you are turning and reduce the number of turns the driveshaft makes. If you lift just one tire off the ground, then one revolution of the tire will turn the driveshaft a number of turns equal to 1/2 of your gear ratio. Judging by the number that you stated of about 2 1/4 turns, I am guessing this is what you did. You better check again. GlennMc.

 

Thanks for the prompt replies...

I see where I may have gone wrong now. I lifted "both" tires off the ground and spun my power wheel. (1 wheel only)
The other tire didnt move as I turned the power tire very slowly..

So, if my shaft only turned 2.25 turns, than that equals 1/2 of my ratio? So, my actuall ratio would in fact be the 4:56 that I pad for... right?

I am checking again with only one tire lifted off the ground, or I will spin "both" tires equally the same...

Any other reasons for the poor or "non" performance gain from this gear swap that i'm experiencing?

Thanks again...