Possible Transfer Case Problem?

[Cody1018]

86 Cheyv K10, 700r4, np208, 10 bolt c-clip rear end with the limited slip device in it(G80). Ive got what sounds like a pretty serious problem. When i back out of the drive and go on my way down the road and hit about 15-30 mph i get a pretty nasty sounding grinding noise followed by some really violent bangs that shake the whole truck. It sounds like its right under the truck when your driving it. And after you go a little longer it stops and drives fine. Although i do have a slight(faint) rattle type sound. If i were to drive forward the rest of the time it wouldnt do it again. But if i had to back up any amount of distance it would start to make all those noises after about 15mph. But i tried driving it in 4wd for awhile and it never does it, even if i back up and then go forward again. So im not real sure if its the rear end or the transfer case. Any help or insight would be appreciated because i cant drive it the way it is much longer.

[Blazin]

Pull the fill plug out of the rear end, and the transfer case. Stick your finger in, and pull some oil out. Wich ever one has metalic in the oil is where your problem is!

[bake74]

Pull the fill plug out of the rear end, and the transfer case. Stick your finger in, and pull some oil out. Wich ever one has metalic in the oil is where your problem is!

     Also while under there, check your drive lines and u-joints.

[Cabcorner]

   Does the truck have auto locking hubs ?Sometimes they don't disengage properly .

[Cody1018]

Sorry i havnt posted in awhile. ive been really busy with school lately.

Pull the fill plug out of the rear end, and the transfer case. Stick your finger in, and pull some oil out. Wich ever one has metalic in the oil is where your problem is!

I did check the rear end, drained out all the oil and pulled the cover off and there was quite a bit of metal shavings on the magnet. There were also a couple bigger bits of metal as well, about the size of a nose piece on a pair of glasses but flat. you could see where the edges are ruff like it was tore off. Didnt really see any marks on the gears inside though.

The u-joints were all good and moved freely.

   Does the truck have auto locking hubs ?Sometimes they don't disengage properly .

Ya it has auto locking hubs.

[Blazin]

How about the T case? I bought an 86 K20 once that when ever I drove up a good grade it acted like rear wheel hop. After about the fourth time driving out of my steep driveway, and it did this I herd a loud bang, and had nothing. I coasted it back down to the bottom of the driveway. I got out and looked underneath, there was oil pouring out of the center area of the truck. I got down, and looked up at the transfer case, it was busted in half!
I am thinking the chain was slipping. The teeth on the gears were all rounded off.

[Cody1018]

Didnt see any metallic in the transfer case fluid. Will pull the rear differential cover this weekend to see how much metal shavings have accumulated since last time. Need to check the gear ratio as well so i can start looking for another axle.

[Cabcorner]

                    I really suspect the auto locking hubs . I have the same truck and after I shift from 4 to 2wd  I get a lot of noise from the hubs (grinding popping ). I usually have to back up for quite a ways to get them to release ,and it usually takes several times . You and I both would probably  benefit from a manual hub swap and a rear end rebuild .

[Cody1018]

Alright, ill have to try backing up for a ways and see if it helps any. Cause i get a lot of really loud grinding/banging sounds after i back up and go forwards and it doesnt stop unless i slow down. Thats what making me think its the limited slip unit thats gone bad. I also get a repetitive clanking sound now when im driving, sounds two metal pipes consistently hitting each other as i drive forward. Going out to work on it today so ill try backing up like you said and ill also pull the cover again.

[Cody1018]

Starting to think its the transfer. Sounds like the chain in there might be getting some slack in it. I think the grinding sound im hearing is the chain slipping and spinning on the gears. And it catches and causes the banging that goes along with it. And maybe the reason it only does it after i back up and go forward again would be because it spins that chain backwards and gets it out of place therefor causing all the sounds again. Does this sound like a pretty reasonable theory or not?

[Cody1018]

                    I really suspect the auto locking hubs . I have the same truck and after I shift from 4 to 2wd  I get a lot of noise from the hubs (grinding popping ). I usually have to back up for quite a ways to get them to release ,and it usually takes several times . You and I both would probably  benefit from a manual hub swap and a rear end rebuild .

Yep you were right. Started looking for my problem this past weekend and found that one of the hubs wasnt disengaging. That same side i also had quite a bit of wobble in my tire so i fixed that and rebuilt the hub. Also took out the front drive shaft to make sure they wouldnt engage again. Going to order some mile marker hubs to get rid of the auto locking hubs.

[Cabcorner]

 Really I was right ? That almost never happens . Even a broken clock is right twice a day I guess .lol . Glad you got it resolved .