Getrag transmissions have 3 real major problems but they can be solved.

The first is really not a fault of the trans but of the manufacturer of the truck. The pilot bushing that Dodge installed in the early trucks was not even close to good enough to do the job handed to it. They fail usually within 50000 miles, or less, of installation and in doing so cause the input shaft to not have any forward support. This leads to the shaft wobbling around and in turn wearing out the input bearing which leads to too much bearing play which causes the mainshaft bearings to self destruct.

The next problem comes from the rear mainshaft bearing not receiving enough oil. This causes the bearing to seize and spin the outer race in the case. It can be prevented by overfilling the case from 3.5 qts to 5 qts.

The third problem is that the countershaft bearings are not large enough for the application. If the truck is stock power and is never overloaded then they are fine. If you "hop it up" or tow really heavy loads then they are asked to go beyond their means. This is not so much of an issue if you use good oil and overfill as stated above.

I personally like my Getrag and will never trade it for an NV4500. They are easy to rebuild (after you get 'em out of the truck, they're really heavy) and are an all around good transmission if you use good synthetic oil in them ( I use Amsoil 5w-30w) and overfill them.