I have a 99'Tj with stock Dana 30 and 35 axles. I do very little offroading will these axles hold up to 35" tires?  

If you do very little offroading you will not have a problem. You will notice your going to need new gearing if you live anywhere near mountains otherwise you will be spending a lot of time in 2nd and 3rd gear.  

yep and very little gear banging which is usually what takes out the 35 and 30's more so than the 35" tires.  

It is not the force that the drivetrain puts on a set of 35" tires that breaks axles and gears. It is the force that 35" tires put on the drivetrain that breaks axles and gears.

Almost none of these catastrophic forces exist on the street.

A huge force difference is load transfer. Going up a steep hill, much steeper than any paved surface, puts much more weight on the rear axle than the front. In some case the rear axle is carrying 80-90% of the weight of the vehicle.

But even that force will usually be endured. Now add in a little wheel hop. Snap.

The equation for force is: Mass * Acceleration = Force.

Mass, that's easy. The weight.

Acceleration, that's harder.

Most think of acceleration as speed or speeding up. Acceleration is the RATE of Change in speed, not just an increase in speed.

The greatest acceleration exerted on a vehicle is the decrease in speed. And the ultimate is when the vehicle hits a wall. An extreme amount of acceleration occurs at the moment of impact. It is that increase in accelertaion and therefore increased force that wads up a car.

Now, back to wheel hop. When the tire leaves the ground while under power, it accelertates. When the tire returns to the ground, it again accelerates. But this time the acceleration is much greater becuse it is the rotational stopping force of the ground, which is instant. This is called force load or shock load.

As the diameter of the tire gets bigger, so does the mechanical advantage that the tire has on the drivetrain parts. A tire spinning really fast that abuptly stops is the force that breaks parts.

So, things break on the trail that would not break on the street because there is both an increase in weight (load transfer) and an increase in acceleration (wheel hop) that never occurs on the street.

Front axles have the added disadvantage of u-joints on the axle shafts. But an advantage in that they never carry the majority of weight of the vehicle when the most amount of force is being applied.

Front axles break because the axle shaft is at it's weakest when the u-joint is not straight. As in turning. The front can usually endure more wheel hop because of the decreased weight (load transfer). Except when the wheel hop occurs while turning, which is what breaks axle shaft u-joints.  

yep, exactly right there....

what I was getting at was the spider gears, just cause I've seem more bad d35's that have never been off road or had larger than stock tires, the dammage was cause by the way they were driven, I shoulda been more clear there,....  

is there an actual need on 35s or is it a want?  

Hey mud

I don't think you said anything wrong. Slam'n gears delivers a great shock load also. I was just trying to shed a little light on why the street is so much easier than the dirt.

As for the spider gears, people do that try'n to get unstuck. The spider gears are not made to rotate 100 mph like people do, spinning one tire with open diffs.

And then that spinning tire hits a rock buried in the mud and grabs traction, and there you go, massive acceleration and pop.  

Thanks for all the great info!  

Thanks for everyones help. To answer someones question, this is more of a WANT than a need. I currently have 32" BFG muds (2" lift). I have two holes beginning to rust thru on the front fenders, and I was thinking about going with the AEV highline fender and hood with the 35" tires. I know I will need different gears, I believe I have the 3:07. I've read that the biggest gears I can go to, are 3:73 with this carrier. Is this true, and will this gearing give me the same performance as the 3:07 with 32's (sucks)  

you'd be better off to get the proper gearing according to your final drive ratio it'll cost ya 1300 bucks for a gear change if ya have it done so ya may as well get er done right... what tranny do ya have?  

I currently have the Ax-15. I was considering going to the NV3500.  

the ratios are slightly different, the ax-15 is .79 and the nv3550 is .73

4.88's for the 35's is awesome with the ax-15

with the nv 3550 ya can goto a 5.13 and be real happy with the extra 20 hp your engine feels like it has over the 3.07 and 32 combo..  

I don't understand how replacing gears can cost so much? I can get the gears relatively cheap is the price High because of the labor, or are you talking about doing the Super 30/35 kits?  

Ya. It's the labor. $300-$400 per axle. Why do you want to replace the AX15?  

It goes into gear really hard between 1st and second. I took it into a transmission shop and he said there wasn't anything wrong with it. Just a "quirk" It has 115,000 miles. It's been like this for the past year or so. It's not getting worse just annoying. Especially in the winter. He wanted to charge me $2000 to rebuild it. I can get the NV3550 thru Rockland Standard Gear for about the same price, plus installation.