The Nissan Z32 300zx has Window Regulators with Non Replaceable Rollers/Guides, all of the Pivot Points & Rollers become Worn & Flogged Out over time & just like the Glass Rollers, they contribute significantly to the Smooth Operation of the Window.
The Combination Of Worn Window Rollers, Dirty Tracks & a Worn Regulator are the Main Causes of Window Operation Issues, eventually leading to Premature Lift Motor Failure.
With the Ridiculously High cost of Genuine Lift Motors & no aftermarket replacements available, Replacing a Worn Window Regulator should be considered Mandatory.
 
Note: I only keep One Regulator in Stock. When it sells, it takes 5 weeks to restock another from Nissan Japan.