Hi everybody. I love reading these posts... wish I had info to give out!
I have a 99 Z-71 4wd with about 125k. I started home yesterday and after about 20 miles of hwy driving I stopped at a traffic light. Out of the blue, as I took off, when it shifted from 1st to 2nd, it about snapped my neck! It make a "clank" noise and shifted very fast and hard. It did it everytime. I went straight home and parked it. I think from 2nd to 3 was a little rough but nothing like 1 to 2. My neighbor says torch conv. My dad says there is a shift-valve that gets clogged. All I know is I'M AFRAID to take it to a tranny shop... I'm sure I'll be told I need a complete rebuild whether I really do or not. Any input? I will spend some money on it but I need to make every dollar count.
Thanks for reading this!

 

HAS YOUR TRUCK THROWN ANY CODE?

 

No, no code. My truck also has the same problem I have read about on here with the 4wd not engaging when I press the buttons most of the time (need to check those connections on the swithches). It makes the "Check 4wd" come on but that's the only code I can see. It's been doing that for a while now.

 

I had this problem on my 93 after a rebuild so, this may not help but the shop had turned up the pressure to my tranny to make quicker shifts. I don't know much about auto trannys, but it would about knock my teeth out when it shifted 1-2. I don't see how this could be changed without getting into the tranny, but maybe something is loose. I don;t think a tranny shop will tell you you need a rebuild, unless it is slipping. Maybe just cleaning or adjustment.

 

I should have said "Snap my neck" rather than rattle my teeth

Thanks Smoke. I've been reading about the pressure. Can't think of anything that would have made it increase. I checked the fluid... clean & full. I drove it for about 10 min tonight, it was perfect at first, but the warmer it got the more of the clunk I heard. Never got too bad (like yesterday) but I barely got her warm. Does anybody know about "shift valves" getting clogged? My dad said his truck was doing something similar. He had a shop plug the valves and re-drill them? Does that sound right? I don't know... I'm not a mechanic.

 

just an idea and ive run into it before is that you might have a sensor that is causing the problem even if its not turning your check engine light on. tranny codes dont always kicked the light on so have a shop with a good scanner like a snap on modus and make sure theres no codes in there for the tranny. i used to work for a dealership and we had one that shifted hard and it turned out to be a sensor that was bad but it was long enough ago i dont remember which one it was.