Reader Question: I have a 1995 Chevrolet Half-Ton Pickup with a 5.7L and an auto transmission. The problem I am having is intermittent. Sometimes, when I start the truck, the engine starts without a problem.
However, my tachometer and speedometer do not work and I have a light on my gauges that simply says “Check Gauges”. Sometimes it is solid, sometimes it flashes.
That is not the real problem though. The transmission will not go into First gear or overdrive either automatically or with the shift lever.
The transmission can be operated in second or third gear only, and that only works by manually moving the shift lever, reverse is seemingly unaffected. The transmission also shifts extremely hard when I manually move the lever. It will not downshift or upshift on it’s own at any time.
However, sometimes when I start the truck, everything works perfect, for up to about thirty minutes or so and then, my tachometer and speedometer stop working and the shifting problems occur.
Other times it has problems right when I start the truck, and then starts working good in the middle of driving it. I have checked all the connections to the transmission and all appear to be clean and tight. I hope you can advise me of possible things to check, as this is driving me crazy. Thanks in advance.
I think I would first want to inspect or replace the vehicle speed sensor, which should be on the driver side of the transmission. A common complaint with a bad VSS is loss of speedometer and transmission shifting problems. The tach problem you have…not sure if that is related or not, but I would first tackle the Speedo/transmission issue and see what happens.
I am not a transmission mechanic, so this could be some kind of internal transmission problem or an electrical ground issue to the transmission solenoids. However, I have seen a similar complaint with the VSS. It is pretty cheap and easy to replace if you want to just guess at something.
Keep me posted if you do not mind.
Follow up by another reader
I emailed you last Friday about a problem that I was having with my transmission in a 95 Z-71, which was the same problem that a guy named Charles had posted on your website. If the speed sensor does not work, tell him to try replacing the electronic portion of the ignition switch.
I was having the exact same problem, and it fixed my truck. Apparently a bad connection was restricting the fire to the transmission, causing the electronics to malfunction. I don’t know if it will help him, but it fixed mine.