What the heck is clutch shudder with an a.t.?

[Classic300e]

I've got a '93 300e, 92k m. with auto trans. It does not feel like there is a smooth transition between the gears, especially the shift to 4th. When I drive my Cherokee with same miles, I cannot even feel the shifts. The trans expert that rebuilt the tranny said its Clutch Shudder and put in an additive into tranny oil to lube the clutch. Slight change in upshifts but still a noticeable shudder.
Any hints on what it could be?

[bhatt]

Before you put additives in, make sure you do the following first:

1. Drain transmission fluid (including from the torque convertor) and replace filter & pan gasket
2. Check that transmission fluid is at *correct* level (use the search function if you're not absolutely sure how to do this)

#2 above is the most critical. My 300SDL started doing exactly what your car did and it was less than 1/2" low on fluid. I changed the fluid (I highly recommend Mobil 1 ATF) and set it to the proper level. That was 30,000 miles ago and it has been working fine since.

Neal