2 weeks ago my service 4wd light came on and would not shift into any 4wd,,this happened 2 days after a wheeling trip.. the light stayed on for 5 days then went away and my 4wd worked again.. then last Tuesday I drove about 50 miles to work and stopped at the store, shut the truck off went inside and when I came out I started the truck and put it into reverse to back out of the parking spot and when I gave it some gas it just revved up and didn't go anywhere,, like I was in neutral, so I shifted to drive and it did the same thing,, rev up like in neutral,, so I out it in park and it grinds a little going into park. shut the truck off and check the fluid, fluid was fine not burnt no bubbles,, so I started the truck again it does the same thing, just revs in any gear and grinds when putting it back in park. so I had it towed to my mechanic,thank god for AAA, but he looked at it and said that some gear inside the trans was bad so I had to replace the trans. but I have a feeling it has something to do with the service 4wd light being on.. my buddy has a jeep and he put his transfer case in neutral and it did the same thing my blazer did. Is there a vacuum line by the trans/transfer case that could cause my TC to get stuck in neutral randomly like that?
I just don't wanna spend all my money and put a new trans in and it still not work and it be a stupid vacuum line..

 

you can check if the trans is moving fluid into the cooler lines..if not then pump is gone in tranny. mine did samething. i was at a light...rev's kicked up and a no go. i pulled on of the lines and put a empty jug on it and had someone put her in gear..nothing..hence pump/tranny gone. i guess you could get a second opinion, i would. i bought a craigslist tranny for 150 and swapped them. pain in the a$$ job but, you do what you have to.

 

I would get the 4wd codes pulled.... Sounds like the transfer case is in N

 

my mechanic says the sun gear went bad so I need a new trans or get mine rebuilt? how much does it cost to get a trans rebuilt,, or should I get a craigslist or junkyard trans

 

Take it to a second mechanic before you jump on spending the money for a new tranny, just to get a second opinion.
Like if you have cancer, You wont take that one docs word for it, you would get a second opinion.

 

If you never rebuilt a trans before then let someone who knows what they are doing get the job done.Around here price varies so shop around if this is the route you choose.Prices can go $500 for exchange and up to as much as $600 for rebuild depending on if its rebuilt stock or with a shift kit.How many miles os on your blazer and do you plan on keeping it for a longtime.That would determin wether or not to go with a used trans or having yours rebuilt.Im leary of used trans or engines unless I seen how the trans shifted.If you decide to go used remnove the pan and look for debris in the bottom of the pan and how red the fluid is.If theres no debris or less that a half of spoon full you should be ok.One other thing if your going for rebuild have your old torque converter flushed or go with a new one.

 

My truck has 127k and i think I do plan on keeping.it for a while..but i have a question, I've heard that when the sunshell gear goes that you only lose R,1,4 gears.. mine has nothing? It's like the transfer case.is in N

 

Correct when then sunshell goes you only lose reverse. That's what happened to mine. I pulled the tranny and replaced the sunshell and some gaskets. Inspected the planetary gears and other innards of the tranny decided it looked fine. This was my first dive into a tranny and it now has 1500 miles on it and running strong. After pulling the tranny it only took me a few hours to do my rebuild. You can do it yourself if your patient and study. Cost me a total of 250.00