I have stock Dana 30 and Dana 44 on my unlimited X stuffed with 5.13 and Auburn ECTED lockers front and rear. I am currently running 35x12.5 Mickey Thompson Baja MTZ’s. I was wondering what would be the biggest tire size I could run. And if I put chromoly axle shafts would that make them strong enough to run an even larger tire.

 

I would not run larger than 35s on a D30.

 

even if i put chromoly axle shafts in?

 

I am running chromoly's in my D30 with 35's and havent broken them since I put them in. I think 37's would be okay as long as you were nice to it but if you like to hammer down in the hard stuff then I think your spider gears will disappear into dust.

 

I just noticed that you are running lockers so the spider gears shouldnt be an issue it would be your ring and pinion most likely to go to pieces.

 

what shafts did you go with?

 

The problem with the D30 is not the shafts it's the small Ring and Pinion (R&P). Your locker already took care of one of the week links, the carrier / spider gears. The next week link is the shafts. When you upgrade the shafts the week link in your setup will be the R&P. The small D30 R&P combined with your gearing makes you R&P particularly vulnerable to breakage as the higher you gear the thinner and weaker the R&P teeth become. If you go 37s as is you may break shafts. If you upgrade the shafts and run 37s you may break the R&P and if you break the R&P your whole investment in the axle may go up in a flying mess of metal shards.

 

I went with Tenfactory, they have FULL circle C-clips and the heavy duty 760X u-Joints.

 

thanks for the insight

 

give them a try I really like them, I paid about $650 if I remember right and they have a life time guarantee.