1994 GMC 4l60e transmission shifting problems
I've got a 1994 GMC Sierra 4X4 5.7 I purchased from an older couple. It has been sitting a year. She said years ago they had tranny trouble; it would stay in low. She took it to a shop where she said they cleaned a switch and reset the computer.
After that it worked fine for a long time, then would intermittently have the same problem, then be fine. I got the truck and it wouldn't shift out of low.I pulled the pan, which was real clean, just a very light coating of gray. I changed the 2-3 solinoid, new fluid and filter. I also noticed the speedometer wasn't working. I then changed the speed pickup on the transfer case, which did not help the speedometer.
Now the truck will shift 1-2 manually, but when you put it in drive, it free wheels: nothing at all; no drag or anything. The computer just checks code 12. If you put it in drive, it stays in low. If you put it in low and lift the handle, it will go into second immediately and when you move to drive---nothing.
Will a bad computer do this? there is no governor or TV cable on this tranny....any ideas?
Today I must have gotten my 20 minutes on the computer, because I got error code 16, which is vehicle speed buffer....! I need to know where it is....don't even know what it looks like!
Thanks---Stuck in the 70's