I'm considering upgrading from my 305-70-17 to either 35 or 37 MTR's. I have a D30 front axle with Trutrac and 4:56 gears. The gearing will be ok, but i'm wondering about the D30 holding up to 37's. Most of my off roading is mild to moderate trails.

What do you think ???

 

It's really iffy.

Structurally you will be OK if you buy an axle truss kit from one of the vendors and just brace the crap out of your axle housing. If your a light wheeler, structurally, that's the week point and thus the point you should focus most on.

Mechanically, however, I'm not sure a D30 pinion gear will hold up to the 37's even under mild conditions. Lets be honest, that front 30 pinion gear is tiny, at best. That will be your week point and a complete whore to change out every time you get into a bind. And even if you don't sheer it every time, you will worry that you will.

If I were you, there are plenty of guys on here and other places who have ditched their D44's for a much more solid D60. Find one of their axles and I bet for 600$ or less you will have a plug and play rubicon front axle and wont have to worry about this problem. The way that I see it, the cost of the axle would be worth the wait and eventually save you cost in light of all the repairs that you could be making.

 

For the fifteenth thousandth time! Do it!

 

Should be good for street and dirt roads. If you turn the wheels in a binding situation or bounce when under power your axles will break at the u-joint.

 

I agree. I ran 35's on my TJ Dana 30 with 4.56 gears and an OX locker for years. That was considered a worse version than the curent one. I never had any gear failurs, but I did break a fair amount of u joints. I just carried spares. I should say that I like the rocks so I was probably harder on that axle than you would be. I would tell you not to go any lower though as I have seen many 4.88 and 5.13 failures.