I'm so cheap- I want to lengthen a driveshaft by cutting the tube and slipfitting a slightly larger tube over it and welding the ends (similar) to soldering a copper coupling in the plumbing world. I can cut the tube on a lathe, make the sleeve on the lathe and then semi- balance it there too... is there anything more I should be doing, or should I break down and take it to the driveshaft shop, pay the $60 to have it done right?

Is it a front or rear shaft? Do you drive the truck on the street/highway? If it is a rear shaft and you drive it on the street - I'd get it done by a DS shop. If it's a front - Go for it. I used a front shaft that we built up in a campground and balanced it by eye for 3 years...

Its a rear and it will see the street sometimes.... I should probably quit whining and get it done right.

If your good you can do it. I had my boss over the summer shorten my front shaft after the dshaft shop decided to add an inch to my measurements :shaking:
Rebuilt it on the back of his truck with a welder, grinder, few levels and a digital one, and a pipe jack. Ended coming out like 1 degree off I believe. Drove with it in 4wd just to see if it vibrated and it acually was perfect. Granted this guy has been doing welding and fabrication for over 30 years, and it probably took him half an hour tapping it back and forth before finally welding it all up. If I was left to do it though, I'd take it to a shop and let them do it :D

take two BIG hose clamps and put them 180*out from each other. drive it. feel for vibrations. move the clamps closer to each other one direction. drive it. continue doing this untill you have redneck balanced your driveshaft. this works excellent, but takes some time driving and crawling under yer rig.

I personaly have lengthened my rear shaft twice already and drive my rig on the road a good bit (mabey 3-4 times a week) and it works great for me and never have noticed any vibes (well atleast over the TSL's and beadlocks). If you find a donor shaft for free then just cut the ends off and put your ends on at whatever length you need. We just made one for my brothers rear out of 1 3/4" .250 wall and drove it 80 down the highway with very little vibes considering the 38" TSL's and beadlocks.

I put a cup of steel bb's in my driveshaft. i hope it works like the airsoft beads in my tires. I'll let you know how it turns out after I get the front axles in and it's on the road again.

more important than the balancing IMO is the idea of having a weld/welds in the middle of tube. It seems to me that it would create a weak point where failure could occur. Given the fact that the spliced tube will be stronger maybe weaker, it would be better to retube so you have equal integrity. Just a thought not from actual experience. If you have access to lathe then why not just retube it yourself ?
I suppose you could do it with an overtube if you were doing it at one end or the other. Just not in the field per say.

get it within .010 with a dial indicator and it will be fine