I have a 1999 suburban that has lost all forward gears but reverse still works normal. The other day I was driving and felt a sudden jerk, and then it went back to normal 3 or so miles later i pulled up to a stop light and stopped when it turned green I tried to move forward and it wouldn't in any gear, but reverse worked. It doesn't make any noise it just acts like it is in neutral when it is in any forward gear. I did check and the shift linkage is connected and moving when gear shift is moved. I was able to get it backed up on a trailer and when i got it home I checked the codes and I had a P0740 Torque converter clutch solenoid circuit / open, and a P1860 torque converter Pulse Width Modulation Solenoid Circuit. I reset the codes and it is still the same no forward, but reverse works. I have read that ignition switches can cause problems sometimes, but i have never had the instrument cluster go out which seems to be a sign the ignition switch is failing. Any help you could give would be great. I am having bad luck lately and getting this fixed would certainly help me out.

Thanks,

I have seen ignition switches cause this, they draw too much current and bring the voltage low on the fuse that powers the transmission and they set all kinds of codes. If the codes havent come back it almost sounds like a mechanical failure like the forward clutches. Check the fluid condition, if it'* dark brown and smells burnt you probably have a clutch failure. If the codes are still there it'* probably an electrical issue. Check the big plug at the tranny to see if there'* any corrosion, I'd be starting there.

I checked the plug at the transmission for coroison and it looked great. Do you know what the pinout is so that I could test to see if i am losing voltage due to excessive current draw.

Shaun, that ignition switch issue your talking about, is that the same issue the Blazers have also?