Trans shifting hard when hot

[sazx44]

01 SSEi with 105k miles, 5k miles ago I changed the transmission fluid and the filter because of scheduled maintenance, replacing dex 3 with dex 6 finally, the car shifts great, and about 100 miles ago after 40+ minutes of driving the transmission's suddenly starts slamming gears, it feels like someone is kicking the car each and every time it upshifts. But before then it shifts nice and smooth. Is the trans getting too hot? I don't know what's going on. I have no SES/ABS codes.

[harofreak00]

2000+ Common Problems & Solutions

• Transmission shift harsh/firm when warm
  • Problem: The transmission shifts harsh after driving for a while when tranny is warm.
    Solution: The PCS (pressure control solenoid) is acting up. You might have the code P1811. While the sensor is cheap, it is located inside the transmission and the side cover must be removed to access it. To remove the side cover, the subframe must be lowered to clear the frame rail. It is a very labor intensive fix.
    It has also been said that an aftermarket shift kit can help cure this problem.
    More info: https://tripleedgeperformance.com/harsh ... -dtc-p1811
    Estimated Cost: $40 for the new solenoid, but $400-1000 in labor.

I've installed dozens of Transgo SK4t65e shift kits with very happy customers and no come-backs.

[sazx44]

I thought shift kits made the shifts harder? Why would I want to do that when it's already shifting hard? Or am I mistaken?

[harofreak00]

I thought shift kits made the shifts harder? Why would I want to do that when it's already shifting hard? Or am I mistaken?

From the article I posted:

These kits are not made to create firm or harsh feeling shifts but to help speed up shift timing and keep what the pcm/tcm wants to see in check to prevent code P1811 from triggering.

[nos4blood70]

I have the TransGo Shift kit. I've been using a shift kit in my transmission since about 60k miles. I am now at 228k and have not seen harsh shifts come back in that time.

[sazx44]

Perfect, just put in the shift kit and now the harsh shifts haven't come back and it shifts much better now. thank you!

[craigstyz]

2025 THREAD UPDATE: Got a 2000 SSEi last summer. only 80K one owner Florida car. Gorgeous, but had hard shifts and FAULT CODE P1811. I know the shift kits may work, but are truly a band-aid and not a proper fix. Just had Badger Transmission in Madison, WI replace my PCS. Yes it labor intensive.$45 AC Delco part. Labor with fluid and filter change was $822. The results are dramatic. P1811 is truly an asinine fault code. Erratic performances all over the place. Shift from reverse to park, part throttle upshift and down shifts. converter lockup and unlock. All intermittent and erratic. ALL GONE. A true electric transmission tune up. It is the true repair to the P1811 scenario that many 4T65E have had over the years. I'm a tough customer, but impressed. It was well worth the money I spent.