ABS/Traction control light

How did you determine that the ABS is causing it?

It doesn't make sense, unless it is reducing torque because of traction control. Are you getting abs warning lights, and is there a code(s) relating to the fault.

There is no strategy with the ABS/TC system that defaults the transmission. Usually, in response to an ABS fault, it disables ABS because it is no longer reliable. Here is a brief description.
ANTILOCK Indicator Lamp
The ANTILOCK Indicator (ABS) is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the electronic brake and traction control module (EBTCM). The ANTILOCK Indicator informs the driver that a condition exists which results in turning OFF the ABS function. If only the ANTILOCK Indicator is on, normal braking with full power assist is available. If the BRAKE and ANTILOCK Indicators are on, a problem may exist in the hydraulic brake system. Refer to Brake System Testing in Hydraulic Brakes. Conditions for the ANTILOCK Indicator to turn ON are as follows:

"Â ABS malfunction detected. As previously described, the ANTILOCK Indicator turns ON when a problem has been found in the ABS. The ANTILOCK Indicator indicates that the ABS and TCS have been disabled.
"Â Instrument cluster bulb check. When the ignition switch is turned to RUN, the ANTILOCK Indicator will turn on for approximately three seconds and then turn off.
"Â Illumination of the BRAKE warning Indicator may indicate reduced braking ability.

"Â Illumination of the Antilock Indicator without the BRAKE warning Indicator ON indicates only that ABS braking is no longer available. Power assisted braking without ABS control is still available.

"Â Refer to Brake System Testing in Hydraulic Brakes for diagnosis of any condition which causes the BRAKE warning Indicator to illuminate.

TRACTION CONTROL Indicator Lamp
"Â Indicator in the instrument cluster notifies driver that the EBTCM has disabled the TCS.

"Â Manually disabling the TCS will not activate this indicator.

"Â Indicator is controlled by the instrument cluster, with messages via serial data class 2 from the EBTCM.

Now obviously, I have not experienced the car, so I am just going on what I know here. In the 13 years that I have been with Cadillac, I have never seen a default to second gear as a result of brake problems. Is there a check engine light on? Try this for me. If the ABS light is on currently, with the key on, press OFF and WARMER on the climate panel. The segments of display will light up, and then codes will display by module, alphabetically. Record them codes and post them in a reply. In adiition, does it start in second gear, and stay in second gear, or is it a 1-2 type pattern starting in first?

The name of the shop is irrelevant, and I would not assume you've spent the time to make this up. I just can't understand the relation between the ABS system, and second gear starts. If it could be explained to me, then I would. I was unaware that the car was not in your possession. All I can offer is textbook information, it may make no sense to you. Here is what I have as a list of possibles for second gear starts.

Second Gear Starts
Checks
Causes

1-2 Shift Solenoid Valve
"Â Stuck OFF

"Â Pinched wire to ground

Pressure Control Solenoid
"Â Inoperative

"Â Leakage

"Â Pinched wire to ground

Starts at HI Line only, Driven Sprocket Support
Staked checkball missing

In a situation like your in, I question what the abilities of the shop are. Do they have any experience in this particular transmission, and operating system. If they made mechanical repairs, were they needed, and were they done properly? Obviously, if you have the same symptom before and after the trans repair, it probably did not need the trans rebuild. I have to wonder if all the wiring was checked, and a simple thing like the shift solenoid mentioned in the list of possibles, was checked and exhausted. In your earlier post, you had said that the ABS light was on. If you could, get the ABS fault codes from the shop. I would like to see what they are, so I can try and determine the relevance between it, and the second gear starts.

If you took it to them to address second gear starts, were given an estimate that you authorized, and they performed the repairs but were unsuccessful, then I would assume they need to correct matters. If it is a circumstance of misdiagnosis, that is not necessarily your fault, and you should not have to pay additional, or the previous repairs should be waived. In good business practice, I would think they would explain the situation to you, and leave you the obligation of feeling whether you should fund further repairs. If they are demanding that you have to pay more to move the process further, then you might contact the better business bureau. I don't know the particulars, and I am only getting one side of the story, so I can only offer about as much. Have you contacted the insurance company in regards to the situation, to see if they can provide any insight? Technically, it was their money that funded the incorrect repairs.

We need to start with this issue by scanning for any codes, but we need to be sure to use a scan tool that can communicate with the ABS system.

Here is a video that will help with this:

https://www.youtube.com/watch?v=rTtAnsOlZU4

Once we know if there are any codes then we will be able to make better decisions however, more than likely there is an issue with a speed sensor on the transmission.

I am attaching the info below on this so let's start with codes and go from there.

Thanks