82 sudden wont move

[sdp123]

hey i have a 1982 gmc i just got just a few weeks ago. so i dont really know much at all about the truck except what i looked at before getting the truck. its on a 10 inch lift with 38.5 tsl. with a sb350 with just a little work done to it. and a turbo 350 trans. but anyway it was driving fine, and shifting fine, and going in to gear fine. but just the other day i got in it and started it up and put it in drive and it was like i could feel it go into drive but when i gave it gas it just wouldn't move it was rolling backwards down the hill. then when i stopped i went to put it into park and it was making a grinding noise as if you was to put something in park going down the road. but when i had put it in drive somebody looked under it and the drive shaft acted like it wasn't even trying to do anything. it was just rocking back and forth. and when i put it in park it just acts like its in neutral it wont go into any gear. but its like you can hear the transmission spinning but not grabbing anything to pull. i am so confused of what has happened to it. so i figured i would try out this site to see if anybody has any input before i try taking stuff apart or having to give an arm and leg to a shop to fix it lol. i would highly appreciate it for anybody that has any suggestions. thanks

 

[HotRodPC]

Sounds to me you've got a broken output shaft in the trans, OR a broken input shaft on the Tcase. I'd lean more toward a Tcase issue since normally Th350's don't break output shafts, and especially a little short stubby one. Play with the Tcase a bit and see if you can get it to move. If it don't work in 2Hi, give 4Hi or 4Lo a try for example. This will help in process of elimination or diagnosis. I have a feeling it won't make a difference, but just to be sure. I think the problem is going to be between the Trans output shaft and Tcase Input shaft.

 

[farmerchris]

shift the transfer case out of neutral ?

 

[JimD-in-AZ]

Damn plastic pads on the mode and range forks...

hey i have a 1982 gmc i just got just a few weeks ago. so i dont really know much at all about the truck except what i looked at before getting the truck. its on a 10 inch lift with 38.5 tsl. with a sb350 with just a little work done to it. and a turbo 350 trans. but anyway it was driving fine, and shifting fine, and going in to gear fine. but just the other day i got in it and started it up and put it in drive and it was like i could feel it go into drive but when i gave it gas it just wouldn't move it was rolling backwards down the hill. then when i stopped i went to put it into park and it was making a grinding noise as if you was to put something in park going down the road. but when i had put it in drive somebody looked under it and the drive shaft acted like it wasn't even trying to do anything. it was just rocking back and forth. and when i put it in park it just acts like its in neutral it wont go into any gear. but its like you can hear the transmission spinning but not grabbing anything to pull. i am so confused of what has happened to it. so i figured i would try out this site to see if anybody has any input before i try taking stuff apart or having to give an arm and leg to a shop to fix it lol. i would highly appreciate it for anybody that has any suggestions. thanks

Farmer Chris who answered above is correct... Your transfer case most likely NP208 has decided to shed the plastic pads that keep the mode and range forks in there proper spots. You have more than likely experienced what happens in this situation after a semi hard braking stop. To get your vehicle to move again, just turn the ignition on without starting it, transmission to neutral then run the trans case lever back on down to 4 low and all the way back to 4hi put your transmission back in park and fire it up and it will move again. However it will keep popping out of hi range and into neutral when you do a semi hard brake. you need to get the fork kit to replace the pads on the range and mode forks. Click this link for a good place to get NP 208 parts... You can still drive your truck but anytime you do a hard brake it will happen as the sudden change in momentum will cause the forks to swing and pop into neutral. If your quick enough you can get going again inside of a minute. been there done that it was quite the pain. key is turn off ignition while in drive(it won't shift to park it will just grind) transmission to neutral then work the transfer case shift lever end to end, put in park, fire her up and go..
Jim

 

[HotRodPC]

That's some cool ****. I thought you were SOL when that happened. Good to know !!! Rep Given !!!

 

[sdp123]

Hey I tried that I messed with the tcase seeing if it would move but it wouldn't. It would just when you try to push the gas a little you can hear something winding like something is spinning fast and the truck like rock like as if something is trying to catch or something


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[89Suburban]

Can you have somebody look at the drive shafts under there to see if they are spinning while you try to move it?

 

[JimD-in-AZ]

Wont Move

Hey I tried that I messed with the tcase seeing if it would move but it wouldn't. It would just when you try to push the gas a little you can hear something winding like something is spinning fast and the truck like rock like as if something is trying to catch or something


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What I said in the above post has to be done with the engine off. If that does not work then more than likely you have a broken shift fork as opposed to just having the plastic pads missing....

Then again it is beginning to sound more like it may be the transmission. Those are some huge tires and they can put a massive strain on a TB350. I hate to ask this but have you checked the transmission fluid level..? What does the fluid look like?
Open your radiator cap and see if it looks oily or sludgy... if it does you could have a breach between the trans cooler and radiator. If water gets into the transmission it will slip big time before the soft parts self destruct.
Sounds to me if none of the above suggestion have been productive, its time to drop the pan on the transmission and have a look at what comes out... If it's not full of debris put a new filter in and new Dextron III, button it up and see what happens... If its full of debris, well you now know what happened... Good luck.

Jim