XJ=mistress

I've decided to go full size axels with my Xj
I' m doing the build on a budget so I've got my hands on a 14 bolt corporate (chevy)rear and a dana 60 HP front (ford) I am going to run 4:56 gears and using a np231 transfer case
I've bin told I might have problems with the gear speeds matching up cause of the two different axles is this a big problem ? Or will it be ok ?

ktmracer419

if you are going to run 4.56 gears, then your gears will be 4.56

if you have 4.56 in the front and 4.56 in the rear, then they are the same.

4.56= 4.56

VTJeep

And even if there's a .01 difference, i.e. 4.56 and a 4.55, that'd be fine right?

XJ=mistress

So there shouldent be a difference between a ford 4:56 gear and gm 4:56 ?

ktmracer419

nope, 4.56=4.56

ktmracer419

yup, thats fine. theres a general rule of thumb floating around somewhere, something like if its within a certain percent of eachother.

VTJeep

Here is the latest info I was just told:

Back in the day, Willes used the exact same gear ratio in their front and rear diff's. This caused a subsequent binding between axles that apparently was something like wheel hop when turning on welded gears, but when going in a straight line. It would literally make the vehicles lurch. So some low ranking service member with no college/engineering education, was able to determine that the front end needed to be geared just slightly higher to allow it to cause a slight pull, thus alleviating the binding issue. Hence why we see 4.10 (rear) and 4.11 (front) gears. Apparently.

This is just what I've heard, but I am not gonna argue the logic of the statement. Maybe it's true origins are debatable, but the concept seems very accurate.

XJ=mistress

Sweet thanks just wanted to make sure

xjmarc

What size tires you plan on running cause 4.56 is good for 35s but my 38s are lacking and I feel like I need lower gears. If you're putting tons in for 35s it's a bit overkill and plan on hanging up on the 14 bolt. You won't break it though.

salad

Sounds believable but a load of BS. I can see a slightly higher gear ratio for the front to reduce hopping and binding due to going around TURNS but not straight. Realistically the gear ratio is based on teeth. 10 teeth on a pinion and 41 on the ring... not sure how someone would get 4.11:1 from that

93XJLI

It is. Different axles use different ratios. Idk why. Say, GM is 4.56 and Ford is 4.55. That's it. And it's fine.

VTJeep

But going around turns employs the use of the use of the spool to allow for different rotation speeds of inner/outer tire. And in all honesty, thinking of it like that, if one tire has to turn slightly faster than the other to prevent binding, it just seems like this law of physics would apply to straight line as well.. Idk, I'm havin a hard time letting to of this concept.. :/

VTJeep

Idk if that's what I was talking about. I meant different ratios on the same vehicle. Granted Dana makes the front of mine, while Chrysler made the rear, so in that sense I could see having a .01 difference. But what about a vehicle that runs the exact same axle f/r?

salad

That's correct (by spool I assume you mean differential) but the front tires still turn faster combined than the rear. This is why 4HI is only part time on NP231s. Take a toy Jeep (I hear you Americans can buy them at friggin' Walmart!), or even Lego lol, ink up the tires and put it down on some paper, then measure the circumfrence of the tracks that the tires leave behind. Larger track = faster wheels. Straight line = same track

VTJeep

Haha.. I've confused myself. I am referring to the differential when I said spool. But your explanation of the 231 is throwing me off. 231's don't have the "differential" that the 242's do, which is obviously what allows it to be used on pavement and not cause binding. But what do you mean by "...the front tires still turn faster combined than the rear." So you mean when turning or when going in straight line? Also, I fully understand the concept of the outside wheel making more revolutions than the inner when going in a circle, but making the same revolutions when in a straight line. But the toy jeep on paper is far from an accurate test for this issue. Unless the toy jeep has an TC and R/P's that can engage both axles.. Idk. I'm not tryin to argue! Just trying to make sense of this!