Posted: Sat May 11, 2013 3:22 pm Post subject: How many speeds does my trans have?
So I've been driving my 05 Impala 9C3 car for almost 9 months. Runs great, & I always keep the gearshift lever in "D" which to me is "OD" or 4th gear. So yesterday I was driving around town & decided to leave it in 3rd gear, since I wouldn't be going over 35 mph. Guess what, the car still shifted into 4th gear. So today I drove a little faster & this is what I realized. At 55 mph when I shifted from "D" to "3", the car did downshift a gear, but what I think really happened is the car actually shifted from 4th lockup, to 4th no lockup. When I start from a stop in "3" it shifts 3 times into 4th gear. But when I start from a stop in "D" it shifts 4 times into what I assume is 4th lockup. Is this the way these cars work, or is this how 9C1/9C3 cars are calibrated to shift? GARY
All 4T65Es are 4 speed. While you can set the car to be in X gear, if the PCM figures out you are doing something that can damage the car, it will override. Without a scan gauge to tell you what the PCM is doing, my guess if you are calling the shift from TCC lock to TCC unlock as an additional shift. The torque converter will lock in 3rd and 4th gear.
Protip: If you don't know what you're doing, don't do it.
Since I never exceeded 2500 RPM, I don't think the tranny was upshifting to save anything. But what does make sense is in 3rd, it did go into lock up which seems like an upshift into the next gear, as I watch the revs drop. I didn't know the conv could lock up in 3rd gear. When I had a 70 Z-28, I would hold the trans in low gear, & at 6200 RPM it would upshift into 2nd, even though the gearshift lever was still in 1st. That Turbo 400 wanted to launch the 12 bolt rear through the back seat when that happened. I only did that a few times. So I guess when the shift indicator is in 3rd, but I feel the shift into 4th, it's really locking up in 3rd. Thanks. GARY
I'll just leave it in "D" & not try to figure out what gear it's in. I do notice it seems to hold 3rd gear a little longer when the motor is cold. My GF's 06 Monte Carlo does the same thing. So far both cars shift real good, & both had recent filter/fluid changes. GARY
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