'88 GMC 1500 Transfer Case Operation?

[wizwrath]

Hey guys,
I have a 1988 GMC 1500 4X4 with the TH700R4 auto trans, please tell me the proper operation of engaging/using the transfer case, the problem Im having is when the engine is running and while trying to shift the transfer case gear selector, the transfer case grinds, when the engine is off everything seems fine, does the engine need to be off everytime I select 4X4 option? Ever since I had this truck I never used the 4X4 option.
Could something be broken?
Thanks and sorry for the stupid question.

[leolkfrm]

Are you trying to go in 4 wheel low? or high? are you of the gas when you shift? light pressure should shift it in smoothly.

[huffcop]

I had an '87 Chevy 4x4 and I'm pretty sure yours would be the same. Shift on the fly did not exist back then so if you're moving, you should not be doing more than 25 MPH when you try to shift from 2Hi to 4Hi. Once it is in 4Hi you may go faster.

For 4Lo, you have to be stopped and trans should be in Neutral with your foot on the brake. Come to think of it, everyone I knew that had these trucks back then had a little grinding going on.

There should've been instruction labels on your sun visor that had 4x4 instructions. I take it that's gone now? Good luck.

[FaselZ71]

I had a 85 full size blazer and it always ground alittle going into 4hi or 4lo I always thought it was normal because 4x4 worked and it was an old truck so I thought time had just did it thing t the gears!

[wizwrath]

Thanks a million guys for the responses!!

I try to put it in gear both low and high four wheel drive slowly and started to hear grinding so I stopped, and Im trying it while the truck is stopped and enigne at idle, and tried it while the transmission is in drive, neutral and park, and it didnt want to go into four wheel mode, it was hard and it grinded,
shoould I just yank it hard???
I also checked on the sun visor for instructions but it wasnt there.

[FaselZ71]

Well I guess it's all preference really! Personally if I need 4wd then I'll just grind'em into gear! But there are people who won't use it until it drops into 4wd smoothly! If 4wd works everytime and you can handle the second of grinding I say use it and don't worry about it! My Z71 has the lever on the floor still and soemtimes it goes in but other times you have to really pull on it for it to go into 4wd. I just deal with it because it works everytime!

[leolkfrm]

maybe it needs some use, have you checked the oil level in it? it may be the therm resister kicking in to slow at the axle. I did have one acting up creating a grinding

[wizwrath]

I guess I do Have to try and just yank it, when I try to go slowly it grinds and seems like it dosnt want to go in...
Im extremely **** about servicing the fluids, and I just dropped the transfer case assembly to change the seal and gasket on the adapter...

[leolkfrm]

To determine what is grinding you can disconnect the activator on the front axle, then if there is no grind its actually a problem in the front axle.

[bradrhale]

mine grinds a good bit and then just pops right into the hole. from neutral, i try to let it roll at a creep, less than 3 or 4 mph and let it go in. the book says that it is easier on the tcase to do it that way.