I drive a 1997 GMC Jimmy, with 250k miles (all mine). So, I had to have my transmission rebuilt, and the second time I picked it up (we won’t talk about the first time) I drove it for a couple of days, and was leaving an icy parking lot, and put it in 4hi. I had it in gear at the time, but wasn’t moving at all, and simply pushed the button. It made a grinding sound, then slammed into 4wd. I dropped it off the next day (again), and was told that I cannot put it into 4hi on the fly, that I shouldn’t be doing that at all, that when you have a transmission rebuilt, you shouldn’t ever do that again- Given all of the trouble I’ve had with this highly advertised local transmission shop, I’m not inclined to believe a thing they say- So, I’m asking you all; When I had my transmission rebuilt, did I in fact lose the ability to put into 4hi while vehicle is in gear- let alone moving? I’m not talking about 4lo here, I know I have to be completely stopped and in neutral for that, even my manual says I can go into 4hi safely up to speeds of 45 mph. I really appreciate your answer on this- as I still haven’t picked it up from the last time I took it in, I didn’t have any trouble with 4wd before the transmission rebuild.
Thanks-
Michelle from Indy
ps. The first time I picked it up, my driveshaft fell out. 
Show them the book…if the owners man says you can…YOU CAN. Absolutely… I would be at a stop though just to be kind and gentle to it…but your owners manual has last say.
Thank you, that seems to be the consensus.
Your wheels might have been spinning. You never know. If you were stopped in gear and a rear wheel was spinning, it might have caused the problem.
What is a “highly advertised local transmission shop”? Do you mean a highly advertised national transmission chain?
A couple of things. One is that I figure the more an auto place needs to advertise the more I want to stay away from them. I like shops that are too busy to bother with advertising - b/c it is their word of mouth reputation that keeps them going.
Second, if this is a national chain-type transmission shop, just ponder one question: if you want a really good burger cooked just the way you like it do you go to McDonald’s? What they sell, of course, only resembles beef. And no one there actually knows anything about how to cook. It sounds to me like you might be going back to the counter at McDonald’s saying “but I ordered the burger rare”
Local- not national- Radio ads mostly- everyone in the area knows the tagline sorta thing. They have 3 or 4 shops in the city.
Thank you, I talked to one of the mechanics today, and he drove it home, including highway, etc… and was able to shift into 4 on the fly with no trouble. I’m leaning towards the fact that I was in gear but not moving (maybe a tire that I didn’t feel) was the culprit. I’ll run it through it’s normal paces and see how it acts. I appreciate the feedback