86 Trooper 4x4 comes out of gear after

[chris741]

I just bought it and have changed the oil, filter, air filter, plugs, pcv, etc. It is a manual transmission and there is a little grinding when switching into gears. Also, from a dead stop, I will engage the 4x4 in high mode and after I drive for a few seconds it will slide back out and the dash light goes off. I can actually see the shift lever return to the neutral (or 2wd) position. I don't want to dump alot of money into this, It's basically a junker that needed a little love and I need 4 wheel drive for short trips a couple times a week.

Can I drain out the old transmission fluid and replace it with new? I heard to use motor oil? Any help is appreciated. Thanks.

Chris

[rodeo02]

Make sure all 4 tires are the same / same diameter. You will bind the drivetrain in 4x4 otherwise. Binding will cause the xfer case to pop out of 4x4 mode.
G/luck
Joel

[chris741]

Thanks for the reply. I actually just put 4 brand new tires on the factory rims so that can't be it. Any other ideas?