I have a 1999 GMC Suburban. I believe the transmission is a 700R4. Today when I got to work and parked I noticed that the transmission felt different than usual when I moved it into park. So I moved the gear leaver back to drive and the transmission would not engage. I put it back into park, moved it to drive again and the transmission engaged. Just a little bit ago, I left work to go to the store and it shifted fine at first then in about 10 minutes it would not engage any gear. I put it in park, killed it and started it again. It took a couple of tries but I got it to go into drive and limped it back to work. Up until today I have not had any problems with it. It has not made any weird noises and it has run just fine. What could be the problem? The vehicle has about 120,000 miles on it and it is not just drive that will not engage. When it won‘t engage, it won‘t engage any gear. When it does engage, it engages all of them.
Without feeling hearing the problem you either have a bad shift cable, or you have internal transmission problems, torque converter, trans oil pump. . The other possibility is a bad trans control module. Get it checked out now cause if it is a simple problem you could do major damage continuing to drive it.
The first thing you should do is check your transmission fluid level and condition. If it is low, then your transmission might be leaking fluid and low fluid just might be causing your transmission to do what you are describing. However, if the transmission fluid looks black and/or strongly smells burnt, then you have internal transmission problems and you either need to have it rebuilt or replaced. If the fluid checks out, then I would look at all the wiring going to the transmission. Many times, the wiring can become corroded because of exposure to weather and moisture and mess up the signals from the computer to operate the transmission properly. And, if that's not the case, then you could have faulty shift solenoids or the computer itself might have went on the fritz. Did your engine light come on when the transmission started acting up? If it did, take it to an auto parts store and have them scan it. The trouble code you get might be related to your problem and you can start there.
