I just got a rearend for my truck that kind of just fell in my lap(woo hoo) Anyway it looks like it came from an Explorer. I think this because when I was putting the 5.0 in it I found out that an Explorer rearend is 1 1/2" wider then the Ranger, and it's a mirror image then the one I had. So here's the head scracher; My old rearend was a 3:45 to 1, and the new one says 3:45 on the tag, but when I did the turn the wheel and count the drive shaft trick it's around 1:75 to 1. I'm going to look at it, but that's freaking insane. I was wanting one that was high geared, but that's a little hard to beleive. Just wanted to know if anyone has ever heard of a 7" rearend that was that high geared, or any rearend that high.

 

Ummmmmmmm, Jarod, this is an Oldsmobile site. But generally speaking I have heard the best way to do that would be to lift both rear wheels, use jackstands under the frame, then turn the DRIVESHAFT and have someone count the revolutions of one of the rear wheels to ONE turn of the driveshaft, and you have your ratio. And yes, 1.75:1 is wildly tall, never heard of that.

 

You might want to read my comments in the "transmission" forum about checking axle ratios. If one wheel is on the ground and one is turning freely, the free wheel will turn twice as many revolutions per driveshaft revolution as the axle ratio would indicate. Thusly, if you turn the driveshaft 10 revolutions and the free wheel turns 5 revolutions, your axle ratio is 10 divided by 2.5 ( not by 5), or a ratio of 4.0. Your axle ratio is probably 3.5, and not 1.75.

 

simply pull the pan, and count the ring gear teeth, and the pinion teeth, and divide the ring by the pinion. math is always exact, theres no guess work.

 

True, counting the teeth is surely a positive way to determine axle ratio , if your center section has a cover to pull. I assume the Ford truck axle mentioned above has a cover. Oldsmobile rear axles in full sized cars did not use a rear cover until about 1965, as I recall. Counting the gear teeth in earlier units would involve pulling both axles , disconnecting the driveshaft, and pulling out the center section carrier.