Possible reasons:
1. Low level or contamination of transmission fluid:
* Insufficient or contaminated fluid can result in insufficient lubrication and increased friction, resulting in shock.
2. Worn clutches:
* The clutches in the transmission wear out over time, which leads to slippage and shock when switching modes.
3. Faulty automatic transmission control module (TCM):
* The TCM receives signals from sensors and controls the operation of the transmission. A faulty TCM can result in improper shifting and bumping.
4. Faulty solenoids:
* Solenoids control the flow of fluid in the transmission. A faulty solenoid can cause delayed or harsh shifting.
5. Clogged oil filter:
*A clogged oil filter can restrict fluid flow and cause shifting problems.
6. Mechanical problems:
*It is rare, but possible, that mechanical problems in the transmission itself can cause shock when shifting modes.
What to do:
1. Check the level and condition of the transmission fluid:
* Measure the fluid level and check for color and odor. Dark brown or black fluid with a burnt odor indicates the need for replacement.
2. Diagnose problems with the TCM and solenoids:
* Use a diagnostic scanner to read trouble codes and check the operation of the TCM and solenoids.
3. Replace worn clutches:
*This is a major repair requiring removal and disassembly of the transmission.
4. Clean or replace the oil filter:
* A clogged filter should be cleaned or replaced.
5. Check and repair mechanical components if necessary:
*Special equipment and experience may be required to identify and correct mechanical problems.
Important: Ignoring shift shocks may result in further damage to the transmission, requiring costly repairs.