broke it

have a chrysler 8.25, was attempting to do the rear disc conversion. Took out the 8mm bolt to get the pin out and well it broke off inside the hole.

Any way to get this out or am I totally screwed?

it's the small bolt that screws into the pin to remove the c clips

I haven't been inside of an 8.25 in awhile, but the bolt your talking about is fairly universal. They are hard but they are brittle, I've never seen anybody have much luck trying to drill one (maybe a diamond drill will work?). Depending on where it broke off, near the head or down deeper there are a few approaches I've used with success. If the break is right near where the head used to be, Dremel a slot in the bolt and try a screw driver (after the head is gone most of the pressure on the threads should be gone). If it is broken down deep, you can try a punch and drive it into the pin, it will screw up some of the threads but the top threads will still be OK if you are careful with the punch.
Once I actually drilled a quarter inch through the side of the spider gear carrier, exposed about half the threads on the bolt and then punched it through.
I'm not sure if the 8.25 is the same as the D35, but at least on the last D35 I checked, the hole for the bolt goes all the way through the pin and also through the ring gear carrier.
As far as putting it back together after you have the bolt stub out, I've been lucky and after re taping, had enough good threads to hold a replacement bolt. Or I used a steel pin in place of the bolt and spot welded the ends of the cross pin as insurance.
The next time whack the top of the bolt head with hammer before you start and be careful with that sucker. I remove them with feeling, tap it with a hammer wiggle a little, tap it agian wiggle a little. I've never snapped one off, but have helped remove more bolt stubs than I care to remember.
If I remember correctly Chrysler used some sort of Loc Tite on there cross pin bolts. And the Loc Tite they used was a little too stiff for the application, that was back in the 80's it's likely a non issue now. There is a solvent for Loc Tite available, it may be hard to find, acetone may work.

The exact same thing happened to my 8.8 The bolt starts as a shank that goes through the crosspin. Then there are about 6 or 7 threads that engage the threads in the carrier. As 8Mud said before they use locktite on the threads. But have no fear!!! In most cases the bolt breaks with about 5% of the threads still engaged to the carrier. I was thinking of drilling it but since it was an 8.8 i'd need to take the shafts out to remove the carrier so that idea was a no-go. I went to my parts guy and he told me the info I just told you. He then told me to get a pin or something similar and bend it so it can fit into the hole. While wiggling the crosspin the very little amount that it can start to try to thread out the rest of the crosspin. I ended up getting mine out in about 15 minutes. Good luck!

its broken off way down in there.. no way to drill it out w/o messing up the threads

i got a spring pin from work to stick in and see if i can twist out the broken bolt.. and some small screwdrivers.. guess we'll see

Look on the left side of the ring gear, see if the hole for the retaining bolt goes all the way through the cross pin and the carrier.
If trying to move it with picks or whatever doesn't work out for you. Think about using a pin punch to drive the broken off end all the way through.
Having a replacement bolt handy to compare with might be helpful, you can likely tell from comparing, just how many threads are left on the broken bolt, before it turns into a smooth pin.

An old trick that I haven't tried in years, is to tape a piece of welding rod, leaving a 1/16" inch or so of rod exposed and using a battery and a set of jumper cables to try and spot weld the rod to the bolt. I've actually used this method and was successful on a couple of occasions (though not on a carrier, it was inside the coaxial telescope mount for a 105 MM cannon). I did use 24 volts (two batteries) though. Dipped the end of the rod into some Boric acid flux. You have to have a steady hand or your fubared.