Here is an old write up from Turbo Diesel Register on the history of the Getrag G360 problems and solutions.

Here is the excerpt from Terry aka Mysteryman that I cited, and the link to the forum for tdr members:
The bearing that fails is the rear main shaft bearing.....This happens due to some of the things I mentioned earlier in this thread....

What you have is a Timkin tapered roller bearing pressed onto the main shaft.....the race is then placed into the rear of the case partially sticking out. Then the tail shaft housing goes over the part of the race that sticks out pressing it down onto the cone....There are shims that go between the race and the tail shaft housing that adjust the bearing clearance..

The failure comes when the clearance is too tight (TOO MANY SHIMS)
This loads the bearing too tight.....When the trans heats up things expand...
This causes the race in the case to lock on the cone and rotate in the case...
This wears out the case and causes the trans to get real hot real fast...Then often times the case will crack between the main shaft and the countershaft bearing bores..... Party over !!!

The bearings in the Getrag are Timken tapered roller bearings just like the front wheel bearings. On front wheel bearings you adjust the clearance with the spindle nut....On a Getrag you stack thin shims.....For new bearings you want a +.006 preload . For used bearings you want .000 clearance.....

Back in the early 90's we were having problems with the remans getrag was sending us...I had about 20 or so that we tore down to find out what had happened...I found that all of them had +.030 to +.045 shim packs.....I thought that I was not calculating it correctly or that the failed units were too bad off to be accurate...
I went to the getrag reman plant way back when to get to the bottom of what the problem was..... I pulled 3 off of the line and tore them down to check the clearance....They all had +.030 to +.045 shim packs in them as well..... Oh sh** ! I called for the production manager ....We discussed my findings...He said that they set them up this way intentionally because they felt .006 was too lose and caused excess gear rattle during testing...OMG !!!

I promptly told him that he was to stick to the spec that WE told them to use and that I was going to write my report to my superiors that Getrag was the cause of the failures and should be back charged for the failures of the remans that Chrysler had had to eat in the previous 3 years!

For those of you that have had one of the Getrags apart . You may have noticed the the rear main shaft bearing race was excessively thick....
The reason for this was that when we were testing the very first Getrags we found that under excessive load that the standard race would split and crack the case...So we reduced the size of the cone and had Timkin make a special thick walled race....It worked and hence the reason for the strange heavy race...
The best thing to do is rebuild the Getrag PROPERLY and put it back in....
There is nothing wrong with the Getrag if you know how to build them !
I have written quite a bit on this subject in the past...Look up the posts...

I know that many think that the NV4500 is a better trans....But we did have the 4500 several years BEFORE the Getrags were used...The 4500 was only used for gas trucks originally....We used the Getrag because it was found to be a better trans during testing.....The 4500 was later used behind the diesels...It had a few small changes made to it before it was used in the diesels but that was it....
The 4500 replaced the Getrag for only one reason...cost !

Rebuilding the Getrag is not hard you just have to pay attention to details...
The Getrag's problems were few but vital... The things that made them fail were as follows...
1) OIL LEAKS
A) drain plug dripped , run out or run low on oil
B) No gaskets on early models , more leaks
C) pilot bushing failures,,, bronze was too soft
D) over loading , trailer too heavy
E) too much hp , turning up the fuel/air
F) overheating ruining the oil
G) wrong type of oil , no 90 weight in the Getrag ! !
H) not knowing how to shift , rattling the gears,, too high a gear at too low a speed

2) Poor assembly
A) setting shim packs too tight , Getrag even did this themselves at times
B) uneven shim packs between main shaft and countershaft causing tail shaft housing not to hit squarely
C) bell housing misalignment

In conclusion, I personally have never had a Getrag fail in any of my personal trucks nor have I ever had to rebuild one twice that I built,, I have seen them go hundreds of thousands of miles in fleet trucks without failures.....

If you still decide to replace it with some thing else I would be glad to buy whats left of your Getrag.. I could use the spare parts ...

Good luck and be sure to replace the pilot bushing. Preferably with a ball bearing... The flywheel will need to be bored out for this...I do my own but the guys at South Bend clutch do them all the time for people.....

As for the pilot bushing....Engineering knew it was not going to work before the first one left the plant...But if you did not haul trailers it would work long enough to get out of warrantee....Engineering wanted to use a ball bearing but . We were shot down due to cost ...
In 94 it was decided to go to a Torrington needle bearing...Great in theory but it just made matters worse....They ate the imputs alive....

As for the worn out ends on the imput shafts...What I do is put them in my cylinder grinder and make them round and back on center..Then I make a steel sleeve on the lathe and press it onto the shaft end.... Then I put them in my cylinder grinder again and finish them to the correct diameter for the ball bearing I am going to use ...The tolerance is .0001 ot centerline . And no your Craftsman engine lathe you got from dad is NOT going to do the job accurately enough !

I have to vote for the Getrag G360, my 1993 Dodge has seen it all at 138K miles.  We have pulled 22K lbs, on our dual tandem goose neck & John Deere excavator.  Pulled high centered newer trucks off the trail.  Drag raced punks in various Asian cars.  I push near 40lbs of boost and the trans / clutch holds fine.  There are great pto ports on both side for accessories.  I have write up some where about the early failures in the transmissions giving them a bad name so Dodge switch to the NV4500 which ended up having an even worse 5th gear problem when pulling heavy loads.  Its cast iron heavy duty and reasonable to rebuild. 

I just wanted to say hello to everyone.  I am on various truck forums (Diesels, expedition, Cummins, etc.)  but i think this fits my intended goals more then the rest.  Our dodge has been in the family since new and spent most of its life as a hard working farm truck in salty Michigan.  This past life has driven the repair & upgrade schedule. This has culminated this year with a complete cab failure do to rust.  So right now my mission is storing 2 years of firewood up so the truck can come in for a serious overhaul.  Which will entail complete front clip, bed, and cab removal.  I am so jealous of some of the build threads going forward here! Thanks, for a great site.