That’s the first place to start. I’d have your service tech completely drain the transmission, replace the filter and then refill with the proper fluid (Dexron, is the one I think, but make sure). Be sure that the tech removes the tranny pan lid so that the half-quart or so that is left in the pan is removed from the transmission as well.
Once the fluid is replaced and is at the correct level — double-check this with the dipstick — with your foot on the brake, run the Monte through the gears with your foot on the brake to keep it from rolling. This move is to make sure the fluid gets into each gear correctly.
Next, check Reverse and I think you will be pleasantly surprised that it will work correctly. You see, if a transmission is overfilled it is nearly as bad as being down a quart or so. Since the transmission depends a fine internal pressure balance, if it is too full or if there is not enough that balance is upset and the tranny works harder than necessary.
Even though it is working harder, in either instance, the work doesn’t translate into better. If there isn’t enough fluid, the transmission tries to overcome deficiencies by building up extra pressure trying to push fluid into the spaces it is not getting to because there isn’t enough. At some times, it succeeds and everything seems to work okay, while, most of the time, the transmission slips.
If the transmission is overfilled, then an over-pressure condition is created. This can lead to damage because the transmission fluid is moving with too much force. In this instance, parts like the torque converter, turbine and impeller blades, clutches and bands and even the gearing can be damaged.
It is quite possible, if there is too much fluid, that gears won’t engage at all, giving you the problem you have.
One other important thing to do is have a diagnostic performed. Have your technician use an OBD-II scanner and the proper software to determine if the tranny is throwing error codes to the engine control module (ECM), the Monte’s primary engine computer. The codes are stored there.
It is quite possible that the control solenoid(s) for reverse are shot and that is why your Monte isn’t going into reverse. This will be revealed by a diagnostic. The good news here is that replacing the solenoid or are relatively inexpensive as the solenoid, itself, costs about $175. The labor is the feature that raises the cost to about $550 for both solenoids, if they have to be replaced.
Let me know what happens, I’d like to hear.
