Ok, I mad a stupid, I know. Here's the deal. About four years ago I found that the tailshaft on my rough idling 85 K5 was split, leaking when it was in reverse. JB and a marine putty failed to quick fix, so in came a new 700r4. After a few days I noticed the mounting bolts going into the block through the bellhousing started breaking. It drove fine, KD functioned great, and it had plenty of muscle to the wheels. But the bolts were only the beginning. After going through 5 or 6 grade 8 bolts it snapped a small chunk of the BH off, encompassing the mounting eye at the 2 'o clock position. I initially thought it was just a weak trans, so I sent it back. The new one did the same thing after a week. When I installed the Tx I did put a brand new Tx mount, but the motor mounts are original '85. Also, a few months before the first Tx showed problems, the idle got pretty rough. I replaced the IP, but it continued. I replaced fuel and air filters, the CDV valve, and figured I'd just live with it. But when all hell broke loose with the transmissions, I put the truck on my "when I get around to it" list. Well, now I'm getting around to it. My issues are two fold:

1) What kind of preparation should I do before starting it for the first time in 3 years? I know I'll have to drop/drain/flush/refill the tank, change fuel/oil/air filters. Anything else?

2) Any ideas on what may have caused the breaks?

Thanks for any help.

1. Sounds good. Don't forget good batteries and check for mouse nests in the air snorkle.

2. Nope

Sounds like something is out of balance. Did you check the balancer on the front of the motor ? How did the flexplate look when the trans was out ?
Fuel may be alright. worse thing would be throwing some aglaecide in the tank. Diesel gets growth in it from water but it doesn't IMO go stale like gasoline. I would check the air filter. I wouldn't go changing alot of stuff until you know it runs. Think could have a major engine problem and now you just wasted all that time and money. Just get it running and find the problem.

I agree, I wouldn't drop the tank. The fuel hasn't sat that long.

Before you start it, put a bar under your motor mounts and see how much slack you got......:) figure maybe you don't have bolts anymore......
can't really see your truck from here......:D

Maybe want to see how much play you have in the broken crank also.....