Transmission issues, replacement transmission experiencing erratic RPM spikes and harsh shifting at low speeds?

THEFUTURE

MEMBER
2020 CHEVROLET SUBURBAN
5.3L
V8
4WD
AUTOMATIC
110,000 MILES

Original Transmission failed; suburban would not drive at all. Had a dealer replace it with a remanufactured one, which I supplied. Within 10 to 20 miles of driving with the new transmission it started acting strange, erratic RPM spikes and harsh shifting at low speeds. Took it back to the dealer, they claim it's the valve body, $$$. My original invoice shows only 5 quarts of fluid, I can only assume they did not flush the entire system before installing the new transmission. Otherwise, it would be 11 or so quarts. Question, would this lead to the new transmission acting this way? Thanks

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,973 POSTS

If they did not flush the cooler lines and replace the radiator this could be the problem, if the old transmission came apart and spread metal inside the cooler (in radiator) the metal could have traveled into the new transmission. But let's run the codes to see if any codes are stored, this guide can help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

You are correct on the fluid volume; it should be about 12 quarts of fluid. Did the dealer give you any codes that they found to determine if the valve body is bad? Here is how to change it out in case this is the problem. Check out the images (below). Please let us know what happens.

Images (Click to make bigger)