How to identify Gear Ratio

[think_07]

So I'm going to be searching the salvage yards for a rear end. Most likely a SF or FF 14 bolt. How can I tell what gear ratio the axle has? Anyone know how many teeth are on the gear and pinion of different ratios, is there a casting number or tag that would tell me? I'm looking for a 4.10 or 4.56, anywhere up there. I would hate to buy an axle and find out I need to re-gear it. Also what does a gov-lock look like? Cause I read that I need a different carrier to install a locker if it has a gov-lock. So I dont want that either.

 

[dyeager535]

Take the cover off, rotate the ring gear, wipe the oil off, and look for the numbers stamped into the edge of it. Many posts about them, some with pics I believe.

IMO you have no business buying a used axle without popping the cover off anyways, so it really doesn't make sense to rotate the tires/pinion and counting, looking for stampings in the axle tubes, etc.

Gov-lock pics have been posted as well, 14FF is the one that is most difficult to discern from open/closed. The SF is easy, as the flyweights and gears are plainly obvious.

 

[blazerbones]

look here for 14ff info:

http://www.pirate4x4.com/tech/billavista/14b_bible/index.html

also:
ring teeth/pinion teeth = gear ratio... if you can see both sets of teeth... or
as dyeager aluded to:
pinion turns/1 ring turn = gear ratio... if your axles are locked... or you turn both tires simultaneously (roll forward) on an open diff... etc.

I think I have that right...

 

[blazerbones]

oh... and I LOVE my gov lock so far (street driven a lot... trail driven some) and I understand that 14ff gov-lock is "somewhat more reliable" than the other axles "gov-bombed"...

but for strictly the trail... detroit/spool/WELDED is the way as I understand...

 

[mrdrinksalil]

A trick I use when looking for gears in a junkyard is to rotate the tire one revolution and count how many times the pinion yoke goes around. Thats your gear ratio. Only so many different sets come from the factory so you can get a good idea what set is in the axle without pulling the cover. If its the set you want then go through the time of pulling the cover.

 

[habitatxskate]

A trick I use when looking for gears in a junkyard is to rotate the tire one revolution and count how many times the pinion yoke goes around. Thats your gear ratio. Only so many different sets come from the factory so you can get a good idea what set is in the axle without pulling the cover. If its the set you want then go through the time of pulling the cover.

you can turn the pinion shaft one full revolution and count the revolutions at the hub. about 3 3/4 revs at the hub would be 3.73's.

 

[mrdrinksalil]

you can turn the pinion shaft one full revolution and count the revolutions at the hub. about 3 3/4 revs at the hub would be 3.73's.

Doesnt the pinion spin faster than the tire; hence reduction. Or am i having a brain fart.

 

[Streetgliderx]

no brain fart pinion is smaller hence makes 3 rounds to the ring gears one. <---- just an example not a real ratio.... altho thats might near a 3.o8

 

[mrdrinksalil]

I was right. Habitatxskate is the one with the brain farts