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The Mighty Kael, 2004 Black CTS, Every Option
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Discussion Starter #1
Operating Characteristics of 5L40E/5L50E Transmissions The Hydra-Matic 5L40E/50E automatic transmissions have some unique operating characteristics that customers may not be familiar with. (fig. 8 5L40E, fig. 9 5L50E, fig. 10 5L50E XLR) They have been designed to provide more of a manual transmission feel than other Hydra-Matic automatic transmissions.

These transmissions are used in 2004-05 Cadillac CTS, SRX, STS, and XLR as indicated in the accompanying table. Here are descriptions of the unique operating characteristics.

Normal Mode Operation (CTS, SRX, STS, XLR) -- During normal mode operation, drivers may notice increased powertrain braking after releasing the accelerator pedal. The vehicle will not coast freely when the accelerator pedal is released but will start to gradually slow down as if the brakes were lightly applied. This feels very similar to releasing the accelerator pedal on a vehicle equipped with a manual transmission.

Sport Mode Operation (CTS, SRX, STS) -- Typically, Sport mode delays upshifts. The Sport mode simulates the performance driving of a manual transmission. Under certain conditions, the vehicle will maintain specific gears longer than a traditional automatic would. When driving in Normal mode in 5th gear, depressing the Sport button causes an immediate 5-4 downshift, which will be maintained for ten seconds. In any other gear, no downshift takes place when Sport is engaged. In Sport mode, the vehicle has firmer shifting and increased performance, and the transmission may remain in a gear longer than it would in Normal mode.

Driver Shift Control (DSC) (SRX, STS, XLR) -- The driver manually overrides the automatic gear selection. Various mechanization options for input device and degree of override allowed.

Performance Algorithm Shifting (PAS) (XLR, 2004 SRX) -- Override of usual automatic gear selection during closed throttle high lateral acceleration maneuver. Lower gear is accompanied by near synchronous engine speed control for quick response upon re-opening throttle (enable threshold bias in Sport mode).

TIP: On SRX, this feature is enabled in Sport. On XLR, it is always enabled.

Performance Algorithm Liftfoot (PAL) (CTS, SRX, STS, XLR) -- Prevents liftfoot upshifts while maintaining engine braking during repeated aggressive cornering.

Winter Mode (CTS) -- The vehicle launches in 2nd or 3rd gear instead of 1st, to avoid wheel spin in snow or ice, if selected by the driver.

Shift Stabilization (CTS, SRX, STS, XLR) -- Shift stabilization is used to minimize shift busyness, or hunting between ranges. Based on several inputs and a map of engine torque at various RPM and throttle position, the TCM determines before making an upshift whether the engine will be able to maintain vehicle speed in the next higher range. If it calculates that it cannot maintain speed, it will prevent the upshift from occurring.

Downgrade Detection Brake Assist (CTS, SRX, STS, XLR) -- Shift to lower gear with braking on downgrade based on fuzzy logic rules calculated from a thermal brake model, terrain detection, desired acceleration, vehicle speed, and mass detection.

Adapts (CTS, SRX, STS, XLR) -- Continual comparison of actual shift times to desired shift times. The transmission controls make hydraulic adjustments to assure the actual shift times approach the ideal shift time the next time the shift is made for similar operating conditions of vehicle rpm, engine load, and road load conditions. The adaptive shift process continues for the life of the vehicle, to provide consistent and optimized shifts.

- Thanks to Robert Martin and Chris Anderson
 

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The Mighty Kael, 2004 Black CTS, Every Option
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Discussion Starter #4
what interests me is the for 2004 the srx vesion had the "performance algorithm shifting" while the cts does not.

so there might be some room for tweakage in the code.


-KL
 

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wait4me6920 said:
Interesting... I'm curious, though, about the 2003 CTS - it was my understanding that it has the same transmission as the later versions...
i'm not sure if it has the same transmission, but the characteristics of my transmission (2003 3.2) are identical. when letting off the accelerator i see engine breaking as if i was driving a stick...then a downshift at the end of the coast.

personally, i think they should have eliminated that on normal mode and only had it on sport mode. in normal mode, for a cadillac, i don't want to even feel a shift nor any resistance for that matter...of course it's nice to still have that option with the sport mode.
 

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TripleOught said:
i'm not sure if it has the same transmission, but the characteristics of my transmission (2003 3.2) are identical. when letting off the accelerator i see engine breaking as if i was driving a stick...then a downshift at the end of the coast.

personally, i think they should have eliminated that on normal mode and only had it on sport mode. in normal mode, for a cadillac, i don't want to even feel a shift nor any resistance for that matter...of course it's nice to still have that option with the sport mode.
Hmmm..3x0,
My '04 goes into free coasting when I let up on the gas in the normal mode. In the Sport Mode it stays locked up does the engine braking thing. I would imagine yours should be the same. I suspect somethings not right with your tranny.
 

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RobertCTS said:
Hmmm..3x0,
My '04 goes into free coasting when I let up on the gas in the normal mode. In the Sport Mode it stays locked up does the engine braking thing. I would imagine yours should be the same. I suspect somethings not right with your tranny.
I belive your transmissions are both operating the same but your ideas of "free coasting" are different.

Robert, if you are driving say 35mph and let off the gas, don't you feel a little bit of resistance? Not as much as at 4000R.P.M's like in sport mode mind you, but still moreso than a normal automatic.

One would also notice this engine braking in normal mode as the car downshifts. Going say 45, as the car naturally slows down to 30 (and the R.P.M's hit 1k) the car will downshift, the R.P.M's will go up a bit to say 1.5k and then you feel that engine braking again.
 

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AsAkAs said:
I belive your transmissions are both operating the same but your ideas of "free coasting" are different.

Robert, if you are driving say 35mph and let off the gas, don't you feel a little bit of resistance? Not as much as at 4000R.P.M's like in sport mode mind you, but still moreso than a normal automatic.

One would also notice this engine braking in normal mode as the car downshifts. Going say 45, as the car naturally slows down to 30 (and the R.P.M's hit 1k) the car will downshift, the R.P.M's will go up a bit to say 1.5k and then you feel that engine braking again.
Let me check on the way home tonite. I want to say it disengages. Some years ago the manufacturers came out with lock-up torque convertors to make the auto trannies more efficient. At certain speeds or RPM the torque convertor locks up and slippage is eliminated. It also save on gas. In the Sport Mode I think it stays locked up and you get engine braking just like a manual tranny. In the regular mode I feel nothing. I may be wrong. I'll get back with you.
 
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