Hi, Dem:
I use both the TBM and the SCI asynchronously on the GP32, and have had no conflicts. However, 1) you appear to be running them synchronously, 2) you may not be interrupt driven, as I am, and 3) you may be using a different HC08 family member.
What processor are you using?
Are you running polled or interrupt driven?
When you say it does not work, what types of symptoms are you getting? Is it not sending anything, or might it be sending only one character?
Can you post a code snippet that we can play with?
Hope we can help . . .