Transmission - Hard Shift ????

[FabricGATOR]

Hello,

After a recent towing situation, I have noticed that the transmission does a hard shift from 3rd to 4th. First two shifts seem normal.

I knew that I was pushing Montie towards the limit with the heavy tow. I manually shifted the gears, holding rpm so the next shift would be within an easier transition. Also, I didn't try to break any speed records as I was transiting late at night with little traffic.

What is the A/T switch on the dashboard, and how does it work. How and when should it be used. I did not notice any appreciable difference although I was not quite sure what to look for.

Additionally, I have noticed a situation with the cruise control that may also be a symptom related to the transmission and or sensors. A few months ago, I noticed that the CC would not catch the set speed as it had in the past. Troubleshoot driving I found that I would set it for around 70 MPH and if I let it drift down, that it would begin to accelerate at about a 10% loss.... say around 63 MPH and maintain that setting. Other times it would not catch at all. Holding resume/accelerate is intermittent or would start to accelerate softly then would disengage when released.

Could it be a computer control issue that can be reset? Will the car re-learn my regular driving habits? Would a transmission filter and fluid change fix this? Did I do hard damage to the transmission itself?

2000 Mitsubishi Montero Sport ES with 110,000 miles. 3.0 Automatic transmission 2WD