I replaced my SMG electric motor a few weeks ago and decided to gather some data to see how much the new motor objectively helped my situation. The code thrown by my SMG every time the cog light illuminated was 56 (0x38) "switching-on time of hydraulic unit" for me. This lead me to believe that a new motor would help in my situation. My conclusion was the same as many others: the old motor had become weak and simply couldn't produce enough force to prime the accumulator in the time allotted by the SMG computer. I performed a little test using INPA to gauge how much the new motor actually helped. Here's the details of my test:
Conditions and Testing Protocol:
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Conclusions:
As far as subjective improvement goes, I haven't had too many opportunities to drive recently, but I have been on a drive very similar to one that set off my cog light on a few occasions. In fact, it was probably hotter and I sat in more traffic too. Zero SMG issues on that drive. Overall, this information isn't really anything new for the SMG community, but I wanted to share some objective data in case others have been on the fence about doing the swap. Obviously there are many different SMG issues out there, but I would highly recommend this fix to anyone suffering from this fairly common problem. 100% worth the money, 99% worth the anguish of actually swapping it.
Conditions and Testing Protocol:
- Transmission and SMG Fluid at Ambient Temperature (~70F)
- Accumulator Preload Pressure Previously Measured at 32 Bar
- Old Motor at 154k Miles, New Motor From SMG Society
- Shift Between 1 and 2 Until Pump Motor Turns On (I Got 3 Shifts Each Time)
- Begin Stopwatch When INPA Shows Motor Has Turned On
- Stop Stopwatch When INPA Shows Motor Has Turned Off
Conclusions:
- The new motor didn't increase the max charge pressure on these cycles. The motor still shut off when the accumulator reached 63-64 Bar.
- Because the max pressure didn't increase, I still got 3 shifts for each charge cycle.
- Most importantly, the new motor was able to complete the charge cycle 33% faster!
- The new motor is also much quieter, not that it matters when the engine is on.
As far as subjective improvement goes, I haven't had too many opportunities to drive recently, but I have been on a drive very similar to one that set off my cog light on a few occasions. In fact, it was probably hotter and I sat in more traffic too. Zero SMG issues on that drive. Overall, this information isn't really anything new for the SMG community, but I wanted to share some objective data in case others have been on the fence about doing the swap. Obviously there are many different SMG issues out there, but I would highly recommend this fix to anyone suffering from this fairly common problem. 100% worth the money, 99% worth the anguish of actually swapping it.
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