Gears or Gears?

[jeeperwilly]

It's that time in my jeeps life to regear. I'm moving up to 33's or 35's. I'm not to sure yet, but my original plan was 33's and regear to 4.56's. I'm starting to hesitate on that notion, and think 4.88's would be better. I currently run 4.10's and 31's with a 2.5. I was also told that going anything over a 4.56 in a D30 and the gears actually get weaker. Not to worried about the rear since it's getting upgraded to a D44. Any idea's? Give me the good, the bad, and the ugly.

 

[Bounty__Hunter]

Go with the 4.88, anything less isn't worth the time and money for the small amount of change from 4.11.

The pinion gets significantly smaller, but it's really not an issue with the 2.5L engine. Should you have 4.0L or v8 power, then it's an issue. Especially since the rear axle will be taking the majority of the power and weight transfer, and you're upgrading it, you'll be fine.

I'm going from my 2.5L and 4.11 to 5.38 gears. Of course I have to swap to front and rear D44's to do it, but for me that's the best ratio for 34" or 35" tires.

 

[Utah_jeepster]

4:88's in a dana 30 is asking for trouble when using 35 inch tires. The pinion is so small that it becomes the weakest link. And its not asking if its going to fail, but when. And when it fails its going to be under a load, a load when your off roading and really need it.
If your going to go to 4:88's I would look into changing the D30 for a D44.
I have seen them fail time and again in a dana 30, even with a 2.5L.

 

[Bounty__Hunter]

Would those failures have all been on slickrock with traction at a premium? I've never seen one fail here in the Midwest, maybe due to the totally different types of terrain.

IF you're going to swap in D44's to get the correct gearing, go lower than 4.88.

 

[jps4jeep]

question, do you have a auto or a 5 spd?

Combo's I have had good luck with
33" tires-5spd-4.56's
33" tires-auto-4.88's
35" tires-5spd-4.88's
35" tires-auto-5.13's

note.. If your gonna go to 35" tires and re-gear I would consider up-graded/swapped in axles. especially if you lock them, the d30/35 combo will survive on the street, butked offroad, snapping is only inevitable.

 

[Utah_jeepster]

Would those failures have all been on slickrock with traction at a premium? I've never seen one fail here in the Midwest, maybe due to the totally different types of terrain.

It is true that slick rock puts the most strain on the gears. yet I have seen failure in mud, sand. and snow as well. Most failures happens when a spinning tire finds some traction and 'locks in'. The torque literally shears the metal at the weakest point. In a D30 this happens at many places but in the case of 4:88 gears its the pinion most often, since the smaller head diameter of the pinion has less support in and around the helical gear section.

The higher gear range (4:88's) transfers allot more torque than the D30 can handle sitting on 35's. The lowest gears I would ever go in a D30 is 4:56 leaving the U-joints and yokes as the failure points. I personally carry spare short and long shafts knowing this is where I will most likely break my jeep on wheeling trips.

Please note: Most of the D30 failures I have seen have been jeeps sitting on 35 inch tires, and the driver putting WAY too much right foot on the skinny pedal. And yes its been on slick rock (thats all I really have to play on here guys).


jps4jeep: I have a D30 front and D44 rear. I run 4:56 gears and tera-low on my 2001. Any lower and driving would cause me to sell my house just to pay for the gas it would cost me to drive it into work for a week.

The newer D30's equipped with ABS system have stronger shafts and u-joints, capable of holding up to the 4.0L on slick rock. If I was going to swap in a larger motor I would change the D30 to a D44 or better, no questions asked.

 

[Bounty__Hunter]

question, do you have a auto or a 5 spd?

Combo's I have had good luck with
33" tires-5spd-4.56's
33" tires-auto-4.88's
35" tires-5spd-4.88's
35" tires-auto-5.13's

Good chart, if you have a 4.0L. This jeeper has the 2.5L 5speed which should go a little lower than what you recommend. Going from 27" tires and 4.11 gears to 33" tires and 4.56 gears isn't changing the gear ratio enough to offset the change in tire height.

I still recommend 4.88 minimum with 33" tires, you'll hardly notice any less of a gear change and it'll be wasting money and time.

 

[jeeperwilly]

Thanks for the input guys. I tend to wheel with a bit more finess then most. I like to pick a line and take my time rather than use what little bit of a skinny peddle I have. Sound's like a D30/D44 combo with 4.88's and 33's will work just fine for what I'll be doing. Besides, if the front craps out, time to replace with a D44.

 

[jps4jeep]

My bad, for some reason I thought I saw 4.0, went back and yup there it is, 2.5. My Bad for the mis-direction.

also, a 8.8 would be a similar swap as the 44 would be, but you get rear discs, there are other Pro's and Con's to each, but thats subject for a new thread.

 

[jeeperwilly]

I was thinking about a 8.8 or even a 9, but I found a D44 out of a Cherokee for 50 bucks. Can't go wrong for that price!