Sometimes you just need to ask for help...

//*****************************************************************************
//  Changes I had to make:
//  1) I had to remove the like-named routine from Serial3 !!!
//     void uart2_status_isr(void) {
//*****************************************************************************
#include <kinetis.h>

enum {
    cPin_OnTeensyLed      = 13,
    cPin_TxDriveEnable    = 24,
    cPin_RxDriveEnable    = 25,
    cPin_UartTx           =  8,
    cPin_UartRx           =  7
};

#define cBaudRate       10000

#define cIRQ_PRIORITY     64

int volatile transmitting;
uint32_t volatile     mDmaErr;
int volatile          mTxCycleCompleted;
uint32_t              mLedTimer;


    char cMessage [] = "\x3C\xFF\xF0\xFF\x00\xFF\xFF\xFF\xFF\xFF\x00\xFF\x00\xFF\x00\xFF\x00";

//*****************************************************************************
void dma_ch10_isr(void) {
    mDmaErr |= DMA_ES;
    DMA_CINT = DMA_CINT_CINT(10);    // Clear interrupt

    UART2_C5 = 0;   // Clear C5[TDMAS]
    UART2_C2 = UART_C2_TE | UART_C2_TCIE;   // | UART_C2_TIE;
}

//*****************************************************************************
void uart2_status_isr(void) {
    if (UART2_S1 & UART_S1_TC) {
        transmitting = 0;                 // Report our completion; // TODO: Make better!
        mTxCycleCompleted = 1;
        digitalWrite(cPin_TxDriveEnable, HIGH);
        UART2_C2 = UART_C2_TE;
    }
}

//*****************************************************************************
void startTx(void * iTxAddress, uint32_t iTxLength) {
    DMAMUX0_CHCFG10 = 0;
    DMA_CERQ = DMA_CERQ_CERQ(10);

    digitalWrite(cPin_TxDriveEnable, LOW);

    transmitting = 1;

    DMA_TCD10_CITER_ELINKNO = 
      DMA_TCD10_BITER_ELINKNO = iTxLength;                          // BITER & CITER, which must match!
        
    DMA_TCD10_NBYTES_MLNO     = DMA_TCD_NBYTES_SMLOE |              // Minor Loop Offset --> Src  ENABLED
                                                                    // Minor Loop Offset --> Dest DISABLED
                                DMA_TCD_NBYTES_MLOFFYES_MLOFF(1) |  // Increment Src addr by 1
                                DMA_TCD_NBYTES_MLOFFYES_NBYTES(1);  // One byte at a time!


    
    DMA_TCD10_SADDR           = iTxAddress;   // TCD Source Addr
    DMA_TCD10_SOFF            = 0L;           // TCD Signed Source Address Offset
    DMA_TCD10_ATTR            = 0L;           // TCD Transfer Attributes
    DMA_TCD10_SLAST           = 0L;           // TCD Last Source Addr Adj.
    DMA_TCD10_DADDR           = &UART2_D;     // TCD Destination Address
    DMA_TCD10_DOFF            = 0L;           // TCD Signed Dest Address Offset
    DMA_TCD10_DLASTSGA        = 0L;           // TCD Last Destination Addr Adj

    DMA_SERQ = DMA_SERQ_SERQ(10);

    DMA_SERQ = DMA_SERQ_SERQ(10);
    DMAMUX0_CHCFG10 = DMAMUX_ENABLE | DMAMUX_SOURCE_UART2_TX; 

    UART2_C5 = UART_C5_TDMAS | UART_C5_RDMAS;   // DMA enablements
    UART2_C2 = UART_C2_TE | UART_C2_TIE;        // Tx enabled, IEs (interrupts) needed for DMA

    DMA_TCD10_CSR = DMA_TCD_CSR_INTMAJOR;
    DMA_TCD10_CSR = (DMA_TCD_CSR_INTMAJOR | DMA_TCD_CSR_START);
}

//*****************************************************************************
void setupUartAndDma() {
    SIM_SCGC6 |= SIM_SCGC6_DMAMUX;
    SIM_SCGC7 |= SIM_SCGC7_DMA;

    // We're assuming our TCD is inactive!
    DMAMUX0_CHCFG10 = 0;  // Tx
    DMAMUX0_CHCFG11 = 0;  // Rx

    DMA_CR    = DMA_CR_EMLM | DMA_CR_ERCA;
    DMA_CERQ  = DMA_CERQ_CERQ(10);
    DMA_CEEI  = DMA_CEEI_CEEI(10);
    DMA_CINT  = DMA_CINT_CINT(10);

    if (DMA_ERR & DMA_ERR_ERR10) {
        DMA_CERR |= DMA_CERR_CERR(10);
    }

    transmitting = 0;
    SIM_SCGC4 |= SIM_SCGC4_UART2;
    UART2_C2 = 0;   // ONLY after clock is on! Don't ask me how I know...

    CORE_PIN7_CONFIG = PORT_PCR_PE  | PORT_PCR_PS  | PORT_PCR_PFE | PORT_PCR_MUX(3);  // Rx
    CORE_PIN8_CONFIG = PORT_PCR_DSE | PORT_PCR_SRE | PORT_PCR_MUX(3);                 // Tx

    uint32_t divisor = (((F_BUS * 2) + ((cBaudRate) >> 1)) / (cBaudRate));

    UART2_BDH = (divisor >> 13) & 0x1F;
    UART2_BDL = (divisor >> 5) & 0xFF;
    UART2_C4  = divisor & 0x1F;

    UART2_C1     = 0;
    UART2_S2    &= ~0x10;       // No Rx invert
    UART2_C3    &= ~0x10;       // No Tx invert
    UART2_PFIFO  = 0;

    NVIC_SET_PRIORITY(IRQ_DMA_CH10, cIRQ_PRIORITY);
    NVIC_ENABLE_IRQ(IRQ_DMA_CH10);

    NVIC_SET_PRIORITY(IRQ_UART2_STATUS, cIRQ_PRIORITY);
    NVIC_ENABLE_IRQ(IRQ_UART2_STATUS);
}

//*****************************************************************************
void setup() {
mDmaErr = 0L;
mTxCycleCompleted = 0L;
mLedTimer = 0;
    pinMode(cPin_OnTeensyLed,   OUTPUT);
    digitalWrite(cPin_OnTeensyLed, LOW);

    pinMode(cPin_TxDriveEnable, OUTPUT);
    pinMode(cPin_RxDriveEnable, OUTPUT);

    setupUartAndDma();
}

//*****************************************************************************
void loop() {
    if ( ! transmitting) {
        delay(20);
        startTx(cMessage, 17);
    }
}