6L80 logics

[PlymouthBarracuda]

Sirs, could you please advise me the logic of the 6L80 transmission when you turn it into the manual mode?

Approximately at 40 - 70 mph periodic vibrations and shaking are felt, which spreads from the engine to the differential. This trembling disappears when I switch transmission to the manual mode.

Also, sometimes, not constantly, I can feel shaking at the 18-25 mph, especially on climbs. Tachometer readings are smooth and do not jump.

At first I thought about the AFM system, but I was told here that it could be a torque converter, which is turned off in manual transmission mode through a special solenoid in the TCM module

[chevy pilot]

At what rpm ?

[PlymouthBarracuda]

Originally Posted by chevy pilot

At what rpm ?

Approximately at 2000-2300. It's very good can be felt during cruising with constant speed on highway. Shaking looks like "yes-no yes-no", issue is not permanent .

Vibrations definitely and steadily disappears at 66.5 mph on D/S modes or in manual mode on any speed

[chevy pilot]

In manual mode not vibrations in 2000-2300 rpm ?

[PlymouthBarracuda]

Originally Posted by chevy pilot

In manual mode not vibrations in 2000-2300 rpm ?

no... they dissapear in manual mode on 5 and 6 gear. But in the traffic on 3-4 gear this trick doesn't help. Also these vibrations dissappear strictly beginning from 67mph on any transmission modes.
I suspect that the issue is with torque converter

[chevy pilot]

Have you tried drive with a scanner ?
It shows converter slip in %

[GenesisCoupe]

Originally Posted by chevy pilot

Have you tried drive with a scanner ?
It shows converter slip in %

Do you know the part number of the TCM solenoids ?

Somehow I saw a video on YouTube where one dude cut the TCM and changed them all, he said that these are ordinary solenoids from Bosch.

Refurbished TCMs cost inadequate money, there are a lot of such offers on Ebay, but there are zero guarantees

[chevy pilot]

Originally Posted by GenesisCoupe

Do you know the part number of the TCM solenoids ?

Nope.

[PlymouthBarracuda]

Originally Posted by chevy pilot

Have you tried drive with a scanner ?
It shows converter slip in %

No slip was found. Today we drove with a scanner, during vibrations and shaking on the slopes of the road slip was within tolerance, no deviations at all.
I took the torque converter off to check anyway. After cutting it, TC was found in perfect condition without the slightest wear.
I was advised to look for the cause in the engine, but I don't know where to look