We do not recommend putting the 4.70s in the front case unless you use a 23-spline version of the dualcase adapter and run a 23-spline input gear in the 2nd case. If you go 4.70 in the front case and then 21-spline 2.28 in the 2nd case, then please drive the vehicle with care while in 1st gear Ultimate.

We've seen numerous 21-spline input failures, and actually when we first got the 4.70 gears back in '97, it was convinent to be able to sell complete Crawl Boxes with 4.70s already installed. Then you could just basically "bolt-in" an Ultimate setup.....and thats when we started busting up 21-spline inputs. The first 5 or whatever Ultimate Crawl Boxes we sold all came back and we had to eat it. I think we ended up building complete 4.70 transfercases and a complete 2.28 Crawl Box and assembling the two together and then returning it as a complete Dual Case Ultimate, not an Ultimate Crawl Box. We ended up wasting alot of time and money there, and hopefully you can avoid that too....