Must be talking about different studders/shudders...
That is the problem of mixing real and fake words to describe anything, there is no common ground for interpretation. The real meaning gets lost by dilution.
Shudder is pretty definitive. When used in a discussion about TC performance and shifting there are not a lot of other conclusions to draw given the known problems. A shudder on a shift\lock is bad news and not a normal occurence. If it is not a shudder then that description should not be used, or, heavily qualified by the user to denote its intended use.
"Studder" is a fake word that has no communal basis for interpretation. Since it doesn't exist for the larger population the meaning can only be inferred.
It only has a definite meaning to a small subset of the whole, and, even then the definition can differ. Since it was used in conjuntion with "shudder", and there is no further qualification of the description, the inference is it relates in some way to a common problem of the TC going bad.
Further discourse reveals the "studder\shudder" is also being referred to as a "double step" in the shifting. More qualification that was missing originally, but, still vague enough it is not defintive. "Double step" would seem to indicate doing something twice when once is expected. That leads to another common failure more succinctly described by "shuttle shift" whereby the transmission shifts back and forth rapidly when only 1 shift is expected. That condition is also not normal and indicates problems somewhere.
Lacking adequate common definitions, it is still possible to infer meaning based on experience. Another meaning to "double step", and with a long stretch of imagination the studder\shudder description, could be the standard shifting routine when the transmission shifts from 3rd to 4th. Since the 3-4 shift is not a single step it is frequently mistaken as a problem, and, depending on the situation the results can vary. Adding TH to the process changes things dramtically at times.
The basic process to shift form 3rd to 4th is: unlock TC, engage OD, lock TC. With advanced pressures of TH and enough throttle this process does produce some very distinctive results. Nothing unusual in that, its the way it works. Raise or lower the throttle input in these situations will change the way the proces is perceived. As far aa fixing it, since it is not broke the "fix" may have some less than acceptable repercussions. Careful what you ask for.
One "fix" could be a triple disk TC and a shift kit. By design, in TH the lockup on a 3-4 shift is not totally released, only pulsed as the shift happens. A triple disk TC takes longer to lock and unlock than a sindgle. The pulse will generally not unlock the TC. The results of a 1/2 throttle under load TH enaged shift from 3-4 are dramatic to say the least. The positive aspect of this event is the headliner will no longer have any dust that needs to be cleaned off. :-laf
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