Hello, the vehicle is a 1993 Chevy 1 ton diesel 6.2 (non turbo) with
4L80E electronic overdrive transmission. The last few weeks I heard a grinding noise each time I started the truck but I thought it was the starter.The last time I drove it, and after the trans went into overdrive gear, I heard the same metal grinding noise and it felt like the trans went into 'Neutral' and then a loud metal rattle. I backed off the throttle and it automatically downshifted into 3rd gear due to slower road speed.
After stopping for the second traffic light, I couldn't go forward anymore except if I downshifted the gear selector manually into 3rd ('D')
Truck will not move when shift selector is in 'Reverse' or 'Over-drive' (feels like 'Neutral'). Still shifts automatically up and down between
1-2-3 as long as I put the gear selector into 3rd gear 'D'Weeks before this happened, problems developed where I had no overdrive, no torque converter lock-up, often had delayed shifts, and sometimes the trans would shift hard into each next forward gear instead of shifting smoothly.The engine was dirty, so I sprayed carburetor cleaner all around both sides of the fuel injection pump while working the accelerator pedal. (I'm assuming the Throttle Position Sensor is located there?)
I also unplugged the transmission wiring harness to clean out the inside of the connectors w/ carb spray (they had some trans fluid inside them). After that, the transmission shifted like it was new, at the proper road speeds, and the harsh shifts were gone. Overdrive worked again and so did torque converter lockup at 45 mph.
I then drove on a long trip but after about 150 miles I lost overdrive and converter lock up again. Then this problem happened. Does anyone know if it's something like needing to replace an electronic solenoid? Thank you in advance for any input.