I hate to say it but you probily should have purchased a rebuilt transmission assembly if the problem was in the transmission. These things are basically trouble free but sooner or later with age and use all powershifts will fail. The company really doesn't want dealers to work on the internals of the transmission because of the extreme importance of cleanliness and the required tolerences. Newer service manuals do not have teardown procedures even written in them. The company wants the dealer to install on exchange basis a rebuild trans from a factory certified rebuilder. This will become more common in future years as all 70 series transmissions are of similar design and are the Fiat designed powershifts in some other models like the TM/60 series.
I have an 8630 with the dual power gearbox. If I find another I will buy it. The powershifts offer convience over the old "crashbox" unsyncronized trans but you know the manual gearbox will work the same 20 years from now as it does today. Whereas sooner or later the seals on pressure delivery passages to the clutchpacks in the multiple rotating gear assemblies will someday fail and require a rebuilt trans to be installed. The sad part is no tractor company even offers a manual transmission in larger 2wd tractors anymore.