WE'VE MOVED, CHECK OFF TOPIC FOR THE NEW LOCATION :: identifying gear ratios?!?!?!?

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I LIKE IT DIRTY Joined: 18 Oct 2007 Posts: 17

how do i figure out what gear ratio is the front diff of my cherokee? is it in the V.I.N.?

Posted: Fri Dec 28, 2007 7:35 pm

Same as the back LOL! ................................................ Easiest way from your stand point is call the dealer give them the last 6 or 8 of the VIN they can tell you in a couple seconds. What year is your truck and what options have you got in it?

Posted: Fri Dec 28, 2007 7:39 pm

if it's stock a dealer can run your VIN and get the build sheet.

check your glovebox for a sticker that may list build info, my '98 Dakota has one.

also check to see if the tag is still on the diff bolts. It should have been there when new and should list the ratio.

If all else fails, just figure it out by counting tire vs driveshaft rotations. Remember that if you only have one tire off the ground and the other is stopped it will spin twice as fast - which halves your error.... Assuming you have a open front diff, lift one tire, mark it, rotate the driveshaft one full rotation once the tire starts turning and the backlash is taken up. If it goes around 7.1 times, you have 3.55s (7.1/2 = 3.55).

If you have a locker or limited slip, obviously lift both and don't divide by two.

Posted: Fri Dec 28, 2007 7:42 pm

True but he has three ratios really close to one another and I have seen guys make mistakes, worst case remove the cover and rotate the crown gear until you see the numbers imprinted on it like 3911 you devide the 39 by 11 and have 3.5455555 or 3.55 gears. But as mentioned being a 94 the dealer can tell you in seconds if they are not being retarded on you!

Posted: Fri Dec 28, 2007 7:45 pm

3.23 3.55 and 3.73 would be thi likely candidates, right? That's why I like the pick up one tire method - even I can tell 6.4 from 7.1 from 8.4 times around.

Unless it's a one owner truck and you KNOW it's stock I don't like trusting what the build sheet says either. If I ask the dealer my truck has 3.55s Wink

Posted: Fri Dec 28, 2007 7:51 pm

LMAO I do not doubt that you can, but you have no idea how many axles I have sold to people that did that and get them back because they were wrong.

Posted: Fri Dec 28, 2007 7:52 pm

heh. no good.

Posted: Fri Dec 28, 2007 7:56 pm

My personal favourite was well so and so told me.

I LIKE IT DIRTY Joined: 18 Oct 2007 Posts: 17

wow, thanx for all the info guys. i'll start by calling the dealer to see what i should have in there.
this truck has passed hands more than 10 times so who knows whats been swapped in it. mind you it has 246,000 km's (this morning) on it and i'm gradually replacing every piece of the front end out of necessity every few weeks. just happened to be the diff/axle this time.

Posted: Sat Dec 29, 2007 2:57 am

What went in it, I had the axles out of my 85 with over 400K on them with nothing until about a year of wheeling ment a replacement hub bearing.