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Jimmy sitting for awhile, start-up advice

Update: I finally got the jimmy home after a long wait. Good thing, after a month and a half my patience was running thin. This thing is cleaner than I originally thought. No rust in the floors, tail pan, any of the usual spots. I'm extremely stoked.
Got to work on it this week a little. My main objective was to get it started.
Put a new battery in it and checked everything over real good, checked the plugs and replaced the fuel filter, new gas and she started right up. Runs really good but my buddy said it could use a tune-up. Smokes a little on startup, not sure if thats from sitting so long or my buddy says it might be the valve guides.
Tried to get it to move on its own, but no dice. Put it in reverse and heard an extremely loud bang come from the rear, sounded like someone hit it with a sledgehammer. Thats about it for now. I would post some pics, but I'm dumber than a rock when it comes to computers, especially when it comes to multiple pics in a single post.:dunno:
 
A little blue smoke at start up then goes away? Pretty much normal old leaky valve seals. Just keep an eye on it, if it gets bad then you may need to replace the seals.

Trans fluid level is good and it still won't move? That could be bad. Or didn't move cause the rear is locked up/broken/etc?

Let us know what you find.
 
Yea, Brian a little blue smoke then goes away. I'm not to worried right now. I had to put 2 qts of trans fluid in, because the fluid level barely registered on the dipstick. I'm sure thats not a good sign either. My buddy said the driveshaft was turning when it was in gear but the jimmy wouldnt move. That was after I heard the bang.
I pulled the rear out from under the jimmy yest. and took the cover off and found what used to be gears, in chunks, on the bottom of the case. A chunk is missing out of the carrier, and the pinion has a chunk out of it. The gears at the end of the axles have some gouges in them as well. The ring appears to be ok but that will get replaced, too. I really need to figure out the pic thing. Trying to decide if I want to rebuild this rear or find one out of a yard. Only thing is if I rebuild I know what I have.
Last thing is I cant seem to find the tag on the housing that identifies the gear ratio. I have some numbers off the ring, GM85342GC, would that tell me. Do they mean anything to any of you guys? Is there somewhere else I can look? The vin # possibly?
The no. on the axle tube is: BK3 GO30 1
 
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Keep reading around the edge of the ring gear. You will find some numbers that will give the number of driven/drive teeth. Just post them up here, we can tell you what's what.

Easiest and cheapest is to swap out the whole rear axle assembly. They typically can be found cheap if not free in good shape. Or, if you know how to rebuild and set up gears, you can rebuild yours, but it can get pricey.

The right way to do this would be to find a 6 lug 14 bolt semi float axle from under one of the newer body style trucks 88-98 with the same gears as yours. The spring perches and shock mounts will need to be cut off and moved and rewelded, but that axle is much stronger than the one you are replacing. It's worth the work/cost to do this.
 
Thanks for the info Brian. A local gm guy here in town is looking for a rear for me. He has quite a few older gm trucks behind his business. I found the gear ratio using the option codes in the glove box, 3.42. I will definately consider the 14 bolt as I am a welder by trade. Shouldnt be to hard to change. Is the 14 bolt the same width as the 10 bolt? Just curious cause I could take the measurements off the 10 bolt and apply them to the 14. Thanks again Brian I will let you know what goes on. I would like to get this rear end wrapped up this wkend.
 
A 14b from one of the newer body trucks, the ones with independant front suspension, will be 3-4" wider than the original 10b. Which is good because the new rear axle will match the width of the stock front axle and will look better overall.

In case you didn't know, these trucks were built with a narrower rear track width than the front for whatever reason. And it looks kinda funny.
 
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