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