Ok heres the deal. I punched my info into a gear ratio calculator and came up with something way off....hope my tach is inaccurate.


According to the calculator, I have a 3.08-3.18 gear ratio.

What I was using for parameters:

*tire radius - 14"
(275/ 60/ 15)

*mazda tranny final gear ratio - .80

*1650 rpm @ 55mph



So you ask, what the hell makes you think they are 3.55?


Door axle code:

19 translates to 3.55 open rear

axle tag:

S8 38J
355 88 5F29

The differential appears to have never been touched.


Both imply 3.55, I have owned the truck since it had 25~30,000 miles on it, bought it in 98 and know it was used for light towing, no reason to change it to a lower ratio. Also, my speedometer mph in the truck is accurate.


Another puzzle, I rotated the passenger tire one revolution, the driveshaft moved 1.75 revolutions.

What am I missing?

 

That means that you have an open rearend. 1.75x2= 3.5
You have 3.50's/3.55's

 

Thats what I kinda figured but it just did not ring a bell or make sense, I searched and there was no mention of open and half. Guess now I know. Looking back, I must have never owned an open differential vehicle...now thats odd.


My tach must be way off...haha...


Thanks