ok i dont know what type of gears are in my truck, because it has a new rear end,(was done before i bought it) and people talk on how 3.55 gears can be sluggish. well my truck is far from sluggish, and ive buried it in the mud, and it ripped out in 2WD (its chipped and has new trans (raptor i think)) its posi as well, but how can i tell?

 

A search would have led you to the answer. Basically, there is a metal tag under one of the differential cover bolts with the gear ratio info on it. Of course, that is the ratio it had when it left the factory. If a PO changed it and did not remove the tag, it could be wrong.

 

divide the number of teeth on the ring by the number of teeth on the pinion

 

haha, yeah that works good if its laying on the ground.

if the rear end is open (not LSD, or LSD not locking), jack up ONE wheel. mark the drive shaft and the wheel. spin the wheel TWO turns and count the revolutions of the drive shaft. about 3 1/2 = 3.55 3 3/4 = 3.72 4 1/8= 4.10
you have to do 2 revolutions because of how the spider gears change the ratio.

if the rear end is a working LSD, then jack up both wheels. make a few test turns back and forth to make sure both wheels are turning together and not spinning independently. then make the marks and spin the wheel ONE turn and count the revolutions of the drive shaft.

 

well there was a site that you could type in rpms tire size and would tell you close gears... but you have to know what the OD ratio


i have 3.92 gear with 30.5in tire and tach 2000rpm at 67mph... so if people post up there tire size with the gear and a rpm at mph you maybe can figure it out

 

To the best of my memory the O/D ratio is 0.69.

 

and so it would have lots of power with factory gears......If the tire size is close to stock....changing gears doesnt really give you more power ...it just changes your final gear ratios to the pavement kinda lick the difference between upshifting too soon on a stickshift and powershifting... bigger wheels with taller gears equals same power/ratio as lower gears with smaller tires...

 

o ok, now i understand, but i have the 265x75x16 i dont know if those are stock, but its far from sluggish with those, and i know they can handle 35s before you can notice the sluggishness with 3.55 gears

 

with 35's the truck will be very sluggish compared to stock 265's may not even hold or reach OD in town at all...... even 33 inch tires should have 4.10 gears or it will be sluggish. One mans idea of a dog is anothers gas saver and different people who come from different rides or bought it that way might think it got plenty of pep so....

think of it as a ten speed bike...the smallest sproket in the back would be 3.55 and larger ones would go up till 4.56 being largest.....now that small sproket may do great climbing up a hill on a 20" (smaller wheels) mtx bike but your gonna be going a lot slower and working a lot harder to get up that hill on a ten speed.... unless you go up to a higher gear then you have to pedal a bit faster (more rpm's) but it takes much less work and energy to do it (produce more torque or power)....

 

I took some advice from the posts that yall done on the gear ratio. Thank you i didnt know how to find what size mine was. Now that ive taken the numbers off the tags that i found i need more help please. One of the tags reads 3.9 and the other tag i found reads 29?? Not sure what the other numbers are cant really see them.