So I'm towing my tool trailer south on I-5 South in California heading for LA, and Bing! There goes my fifth gear! The other gears still work but I guess it will be time to rebuild a tranny when I get my truck from Matson in Hilo.

Is there danger that the other gears will suffer from metal chunks?

 

You'll be fine, I drove mine 1200 miles without 5th before I fixed it.
An updated mainshaft is the only fix that works long term http://www.standardtransmission.com/dodge.html

 

I drove mine for about 15,000 miles with only 4, no issues whatsoever except the threads had worn off the old nut......

I had the fully splined updated shaft already.

If yours is 4X4, I have beat the snot out of the external retainer, I used the updated nut and then added the prong retainer that is also splined to the mainshaft.

http://fifthgearrepair.com/nv4500repair.html

If you have a 2WD, I know of no comparable solution, so the fully splined shaft is your best option at that point.

 

my friend drove 2,000 miles back home in 4th after the nut fell off, no damage what so ever other than he was pretty worn out from driving so slow

 

Thanks, guys, this forum is a great resource! I talked to the guys in Colorado on the phone, and they educated me. It's no big deal, in fact, as it turns out. Thanks again.