I have an automatic C3 With a v6 motor. It "stutters" from 5 mph to 0 and if you take off like a normal person it stutters from 0 to 12 mph. If you gag on it from the start it does fine. Changed ATF and filter. Used rebuild in a can. (sea foam for tranny) And a friction modifier. Vacuum modulator I have not checked but it does not use ATF. Thanks in advance Boog Out

 

Welcome to the forum


Changing the fluid should have gotten rid of any shudders, it can be caused by debris build up in/on the transmission parts, new fluid should flush it out after a few long drives, 20-30 minute drives

From the description it could be torque converter or one-way clutch, but I would expect one-way clutch issue to also cause shudder any time you shift from 1st to 2nd or 2nd to 3rd, one-way clutch allows the smooth shifting and start off in an automatic, harsh shifting is one-way clutch engaging quickly instead of slowly
So torque converter would be my guess, but only a guess

Debris in dirty ATF fluid gets into parts like the clutch and fluid coupler in torque converter, which causes slipping and grabbing, the shudders

Does it do the shudder in Reverse?

 

It does not shudder any other times but as described above. The fluid has a pretty metallic look to it. Somebody has been in the tranny as the gasket was siliconed on and the magnet was missing. It almost acts like it's shifting/ not shifting into 1st unless we put the foot feet to the floor to start off. Ok out here in the country not worth a $%^& in the city traffic. Bouncing between 1 and 2 maybe? Thanks Boog out