I have a 1998 c3500 with an 4L80E I had the truck go into limp mode and I pulled the codes p0758 and p1860. I just replaced both A and B solenoids and filter. checked the voltage at the fuse, ignition (on the white wire) and at the pass-through plug on pin E all of which have 12+ volts. the truck still has the same issues and I dont know what or where to check anything else. also I replaced 2 ground straps and added 2 more grounds one from the battery to the block and one from the transmission to the frame. previously I had a similar issue and dont remember what the codes were but i had put a small ground wire to the tranny from the frame and it cleared up the issue, it doesnt seem to be the case this time. also i swapped computers and I swapped pmd's and nothing has cleared it up

 

would, could the tcc solenoid cause the shift solenoid code? it seems unlikely both would go out at the same time and I tested the ones that came out and they are both good. I havent tested the tcc and not sure how to really but I am leaning towards electrical. would the speed sensor cause it? my spedo works fine. please help this truck is my bread and butter and I need her fixed by monday..

 

It ended up being the wire connection that went through the firewall under the dash by the fuse box. works great now. thanks for all the help