I can think of at least two recent studies that have explored this relationship. As a starting point, you can read these and get a feel for what questions still need to be answered in regard to transformational leadership and voice. Good luck.
Duan, J., Li, C., Xu, Y., & Wu, C. (in press). Transformational leadership and employee voice behavior: A Pygmalion mechanism. Journal of Organizational Behavior. http://onlinelibrary.wiley.com/doi/10.1002/job.2157/abstract
Detert, J.R. & Burris, E.R. (2007). Leadership behavior and employee voice: Is the door really open? Academy of Management Journal, 50, 869-884.
I fully agree to Lance Frazier, for your own research it might be very useful to capture TL in detail, concentrating on intellectual stimulation and individual cons. as predictors of voice. Plus it might be useful to think of organ. climate (for excellence for instance) as a moderator in the regression. Climate for excellence can moderate for instance the relationship between transformational leadership and team innovation:
Eisenbeiss, S. A., van Knippenberg, D., Boerner, S (2008). Transformational Leadership and Team Innovation: Integrating Team Climate Principles. Journal of Applied Psychology, 93(6), 1438−1446.
Another moderator could be power distance which has been researched in the context of TL and health outcomes in a study with approx. 100.000 (sic) employees by Zwingman et al. (2014):
Zwingmann, I., Wege, J. Wolf, J., Wolf, S. Rudolf, M., Schmidt,. M. & Richter, P. (2014). Is transformational leadership healthy for employees? A multilevel analysis in 16 nations. Zeitschrift fuer Personalforschung, 28 (1-2), 24−51.
good evening, I also am very interested in the TL and employee voice. I have found a couple of studies helpful.
Wang, D-S., Hsieh, C-C. (2013) The effect of authentic leadership on employee trust and employee engagement. Social Behavior and Personality 41(4), 613-624 http://dx.doi.org/10.2224/sbp.2013.41.4.613
also A critique of transformational leadership: Moral, professional and ...
Currie, G. & Lockett, A. (2007) Human Relations; 60, 2; ProQuest Central
pg. 341.
I just completed an analysis of the TL and qualities of, which I have attached.
I think these papers are Important regarding TL and Voice Behaviour (Proactive Behaviour):
Schmitt, A., Den Hartog, D. N., & Belschak, F. D. (2016). Transformational leadership and proactive work behaviour: A moderated mediation model including work engagement and job strain. Journal of Occupational and Organizational Psychology.
and
Den Hartog, D. N., & Belschak, F. D. (2012). When does transformational leadership enhance employee proactive behavior? The role of autonomy and role breadth self-efficacy. Journal of applied psychology, 97(1), 194.