I have a 95 gmc 6.5. I've been living with a shifting from 2nd to 3rd problem for weeks. if i baby the accelarator (ease off the accelarator at 50kph) i can make it change from 2nd to 3rd. -once it changes to 3rd there are no other problems. if the transmision dose not shift to 3rd then the only way is to #1 stop the vehicel, disconnect the computer for a minute or so, reconnect the computer, start the engine and slowly try again till i shift into 3rd then drive as usual. or #2 shift into neutral while driving 50kph or more at high rpms, turn engine off, restart engine, shift into drive. I ran the fault codes and came up with the following: 63-accelarator pedal position 3 circuit high. 68 overdrive ratio error (sec.7a-17c). 85-undefined ratio error(sec.7a-17c). 87-high ratio error(section7a-17c) These are thefault codes that i referenced through my chilton manual for this van. I don't know what the subsections are refering to. I have replaced the solinoids in the trany, tested the tps, and tried a new computer to no avail. Is this trany is shot? http://www.dieselplace.com/forum/smileys/Ermm.gif

With all those ratio codes it does sound like the tranny's shot. Possibly a direct clutch failure.


The 63 code is another problem, when it sets it will default the accelerator position to 35% and will cause the trans to shift the same every time. The TPS could just need to be adjusted