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
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
After stopping for the second traffic light, I couldn't go forward
anymore except if I downshifted the gear selector manually into 3rd
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.