4 wheel drive gearing questions

[bigtooth]

I'm in the process of making a plow rig out of an 1987 jeep cherokee. I need to replace the rear end becausee the ring gear is damaged and I have ran into a couple of questions regarding this whole process:

1) The gearing that is in the differential now is 13 teeth on the pinion and 40 on the ring, most rear ends and replacement gears I can find have 14x43, so:

40/13 = 3.07692

43/14 = 3.07142

Are both these setups considered 3.07:1 gearing or is the higher one 3.08:1?

Also, if I put in a 14x43 setup in place of my 13x40 axle will they grenade when I use 4wd being that my front axle is setup with that much taller gearing? Where talking .0055 of a difference?

Thanks for any insight you may have, i'm new to all of this stuff!

[Charles De Mar]

Better off asking in the hauler section:cheers:

[414Rides]

I am not sure if that small of a differance is going to cause you any issues. However on 4 wheel drive vechicles you need to have matching gear ratio's front and rear so you may be pushing it. But you are not running something like 3.73 rear and 4.10 front which would really cause issues. I will talk to some of my jeep buddies and get you a better awnser shortly.

Well I did some checking for you. Here is the awnser I got......Change them Both. The differance is very minor however it is a differance. The front and rear axle will still be turning at differant speeds. Is it going to grenade.. The awnser was who knows. Is it something you really want to risk. Also they said if you are going to use it as a plow to go 4.10:1.

I hope this helps.

[Crunch406]

While I agree that you should go with lower gearing for the snow plowing, you would be fine running gearing that close especially with as much slipping as snow will allow.

Your bigger concern is getting rid of that D35 rear axle and looking for an 8.25 or an XJ D44.

Try www.NAXJA.org for tons of Cherokee. information.

[adam728]

Many 4wd trucks/Jeep/SUV's do not have the same gearing front and rear. This is becasue the physical dimensions of the axles just may not allow it. The difference is always minute, and one of the reasons you are only supposed to operate 4wd on surfaces with some give to them.

I cannot remember the axle combo, but some Jeeps came with 4.10/4.11. The actual ratio was even closer than that, but when rounding to hundreths that's what comes out. A 0.0055 difference is nothing (0.18%). Having tires on one end more worn than on the other will cause more of a difference than that. A 30" tire worn down 1/8" will rotate 0.42% faster than one with full tread.

Now the real question, are they the right replacement gears? Seems strange that they would have different ring/pinion teeth numbers to achieve the same gear ratio.

[bigtooth]

Many 4wd trucks/Jeep/SUV's do not have the same gearing front and rear. This is becasue the physical dimensions of the axles just may not allow it. The difference is always minute, and one of the reasons you are only supposed to operate 4wd on surfaces with some give to them.

I cannot remember the axle combo, but some Jeeps came with 4.10/4.11. The actual ratio was even closer than that, but when rounding to hundreths that's what comes out. A 0.0055 difference is nothing (0.18%). Having tires on one end more worn than on the other will cause more of a difference than that. A 30" tire worn down 1/8" will rotate 0.42% faster than one with full tread.

Now the real question, are they the right replacement gears? Seems strange that they would have different ring/pinion teeth numbers to achieve the same gear ratio.

This makes really good sense to me, thanks! I think that there are two different types of dana 35 rears, the dana 35 with or without c clips. which doesnt really matter to me, because it looks like i'm not even going to try to fix the old one, but rather find a used rear end with close gearing.

[rustyknife]

yup, tires will cause a much larger difference end to end as stated above, no probs

[Crunch406]

This makes really good sense to me, thanks! I think that there are two different types of dana 35 rears, the dana 35 with or without c clips. which doesnt really matter to me, because it looks like i'm not even going to try to fix the old one, but rather find a used rear end with close gearing.

I would look for a later model Chrysler 8.25 rear, but you will still be looking to regear. Most will have 3.54 gearing which is more what you'll want anyway, then just gear the front to match.

[JustRandy]

Some guys (me included) actually want the front tires turning a bit faster than the rears. The truck will turn easier both in the slop and on hard pack. And when you're going straight, the rears drag just a bit. What you NEVER want to do is make the rears spin faster than the fronts! Much of why you would or wouldn't want differing gear ratios depends on what you're trying to do. Driving on snow on the road... I'd probably want the tires to spin exactly the same speed. This is because I wouldn't want any tires to ever slip... Slipping = sliding sideways and possibly ending up in the ditch. AWD may be better than 4WD on an iced up road.

More reading on the subject: http://www.nwuonline.com/Forum/viewtopic.php?f=19&t=3271&view=previous

[bigtooth]

You guys are great, I love this forum, thanks for the help. I found a D44 in IL with 3.54 for $100 bucks plus what ever it takes to ship it. But like you said i'll have to regear the front, which

I really didnt want to get into, this was just supposed to be a cheap yard rig. I got the jeep from my bro in law for $150 and found a plow for $300, thought it would be a good idea to put the two together

I was thinking of getting this d44 and before I install it have the spider gears welded up to lock the rear end then just taking out the front drive shaft, you guys think this would work

as well as having normal 4wd?

[adam728]

I was thinking of getting this d44 and before I install it have the spider gears welded up to lock the rear end then just taking out the front drive shaft, you guys think this would work

as well as having normal 4wd?

No, it will not, especially plowing. You'll have a hard time backing up after pushing up a bank, and you'll have a horrible time trying to push anything straight. You'd probably be better off with an open diff and 2wd than welded and 2wd.

[JustRandy]

You guys are great, I love this forum, thanks for the help. I found a D44 in IL with 3.54 for $100 bucks plus what ever it takes to ship it. But like you said i'll have to regear the front, which

I really didnt want to get into, this was just supposed to be a cheap yard rig. I got the jeep from my bro in law for $150 and found a plow for $300, thought it would be a good idea to put the two together

I was thinking of getting this d44 and before I install it have the spider gears welded up to lock the rear end then just taking out the front drive shaft, you guys think this would work

as well as having normal 4wd?

I think the last thing you'll want on an icey road is a locked rear end. You'll slide sideways too much unless you drive in ruts all the time (but you won't if you're plowing). Its better to have one front wheel pulling and one back wheel pushing.... and the other two wheels keeping you from sliding sideways.

The best way is to have an arb or ox locker so you can run an open diff most of the time, and if you get stuck, lock the diffs and get out of the hole. But those lockers are really expensive. A lockrite is a cheaper way, but those put all the power to the inside wheel (since they don't have an open diff), which promotes sliding and rooster-tailing.

Re-gearing a d44 isn't too awful bad.... There's a ton of tutorials online to help. I think the worst part is you might have a "crush sleeve" and once you crush it, you can't undo it without replacing it and starting over. Usually, your ring set will have plenty of shims, paint, etc. Check this place out: http://www.ringpinion.com/

Here's one I did a few years ago with a detroit locker and a set of yukon 3.73 gears:

[Crunch406]

Yeah, if you lock the rear and had nothing pulling up front, you'll never make it out of your driveway nevermind plow anything. Definitely regear the D30 to 3.54, not the D44 to 3.07. I don't think your D30 has a crush sleeve unless your XJ is a 2000 or 2001. Rather than regear the 30 though, look for one somebody is selling and swap it in place of yours. Alot of people modify their XJs and practically give the D30 away and most are geared with 3.54s from the factory. You might as well install your lift when you do all this cuz you know you will eventually do it ??