I have a '95 Chevy Cheyenne with a Vortec 4.3 liter V-6. It currently
has 160,000 miles. The truck is in really good shape and runs excellent
until recently. I just had the ignition switch changed, and the module
on the distributor changed. The faulty ignition switch was keeping the
speedometer and tachometer from working. They sat at 0 even while
giving gas. It also caused my maint req'd light to come on. The truck
also did not start in first gear from a stop. The switch kept the
transmission from working correctly electrically.

After getting all this repaired the truck seemed to run fine until I
noticed that it was not going from fourth gear and settling into
overdrive at 50 mph. From driving the truck I can tell by sound of the
engine, and revolutions on the tach, that I am running way too high
rpm's for say 70 mph for example. I brought the truck back to the
mechanic and told them that it was not going into overdrive, and he
checked over all the work that he had done, and told me that he feared
it was an internal problem.

After taking to get another opinion they say that it is an internal
problem as well. I have been driving the truck around for about 3
months now with the diagnosed "internal problem" on the tranny with
no other problems but higher engine revolutions and less mpg's. I am
about to get it overhauled, but wanted to know if it could possibly be
an electrical problem, and not a mechanical problem with the
transmission at all.

If anyone could offer some advice/ knowledge/ information before I sink
some big bucks into getting this transmission overhauled I would
greatly appreciate it.

Thanks, Jonathan