the output shaft is just over 1" wich is plenty of material for a 1/2" bolt and a 1/2" bolt only requires 1/2" of thread so i will only have to drill a 29/64" hole 3/4" deep in order to thread it 1/2" deep
my consern with going smaller is the force of driveshaft pulling on the flange over time may break a small bolt.,im shur everyony has trisd to pull a greesed slipshaft apart befor and the suction makes it difficult at times,imagine trying to do it really fast.

I don't think I'd be worried about the material for the bolt, but I'd worry about the amout of material being twisted in relation from the gear to the drive shaft.  

Granted they make axles larger to get more teath and thusly more surface area to apply torque to, but they also get more strength in the larger diameter.  If you take too much material out of the output shaft you may run the risk of 'pretzling' it

~Nate

ran into a problem today .cant find a drill bit that will drill the herdened shaft,once i get it started i should be ok,shafts are usually only hardened on the surfase so i may have to grined .1 or so off the end of the shaft to get to the solft stuff
as far as pretzeling the outtput shaft it would also have to twist the yoke  and their will be 2.5" of yoke on the shaft,IMO it will be ok if i can get the shaft drilled and tapped
and i never said it would work anyway i just said i was working on it ,i appreciate the input ,i am just experminting ,if it works it may give people more options for their rigs ,may even see some track trans in samurais, who knows ,im just playing with some ideas

Are you using a Cobalt or Titanium Nitride
Drill Bit ?? High Speed Steel won't touch that.

What size are you starting with ??

started with 3 ,1/4 " cobalt bits ,didnt touch the shaft rounded the bits off :-/

Might need a Diamond tip to get
thru the hard surface, I didn't think
the shaft would be that hard, hard is
brittle too you know, I like to start with
a small bit for big holes, then work up
3 or 4 bit sizes to the size I want, Try
a titanium nitride, see if it cuts it, I would
start with a 3/16 or 5/32 drill, slow speed
so you don't burn the end off, and see how
it goes, if not then a diamond or a die grinder
with a small silicon carbide stone to get thru
the hard surface, and you might want to rethink
a 1/2" hole if it's this hard to cut  

I still think an 8mm or 1/4" grade 8 bolt
would be quite adiquate, you could compromise
with a 5/16" bolt, that's 8mm, I was wrong 1/4"
is a 6mm, and I think that is a little small

Wild

dang,sorry it took me so long to get back here :-/ But hey thanx for the info and heylet me know how yours turns out! and i shall pass some info back to you on my situation mesjr2004

started working on it again today , split the cases and took my output shafts out so they can be chucked up in a lathe , ive got my yokes and flanges done , im going to try to drill a 3/8 hole and silver solder a grade8 stud in it , im worried about breaking a tap off in it :-/

Silver Solder doesn't like steel much,
you will have to braze it in, and that
will weaken the shaft, I think a good
shop can do this work, I would try it
myself, but I'm like that

Good Luck mesjr

Wild

ok their done ! the process was a carbide boaring bar (well two actually ) and slow .the case hardening is about .030 deep . once you get past that its buter. a reliefe was also cut to keep the hardined meteral away from the tap. i used a 3/8 fine thread tap and will still stud it so the threads in the shafts arnt being titned and loosned .i will use blue locktite in the shaft and red on the nut holding the flange on. id post picts but i havent charged my batery since moab