IDPARTS replied with the same confirmation. I think for the sake of CONFIRMING this, I will install the DMF126 even though my flywheel on my JSW has 129 and I will report back.
Just for grins, here is the reply from IDPARTS:
Thanks for reaching out. I'm in charge of all fitment and listing information. You've done your research so I'll join you down the rabbit hole to give you all the information we have:
Years ago we found that VW listed *two* flywheels for the common rail TDIs. They were the same diameter, so we set out to find out what was different about them. We took a collection of cars and matched the VINs to the flywheels to see what the difference was. Importantly, different vehicles from the same year/model/transmission configuration will show in the VW database as using different flywheels, even though all the other equipment is identical.
We contacted LUK and found out about the different number of teeth. The only function of the teeth on the flywheel is to interface with the sprocket on the starter, so we researched the starter versions. Again, regardless of what flywheel was noted in the VW database, they all used the same exact starter with the same number of teeth. This meant that, to VW, the same starter could be used for both the 129 and the 132 tooth flywheel. Over the full circumference adding three teeth makes a miniscule difference in the tooth spacing, so this makes sense.
If the flywheels were physically identical other than the tooth count, and the tooth count didn't matter to the starter, what was the reason for the two flywheels? We researched further...
After further digging we discovered ONE very important difference - the DMF181 flywheel is specified for vehicles equipped with Auto Start/Stop, while the DMF 126 is NOT specified for vehicles with start/stop...this was especially interesting because no manual transmission TDIs were ever equipped with start stop, so the 181 *sort of* isn't correct.
Since we've seen this with other parts, our working assumption is that VW put whatever flywheel they had available in inventory at the plant at that time in. Since the 181 would work, if they ran out of 126s then they would put in 181s. We've also seen literally *HUNDREDS* of places where VW parts listing by VIN is incorrect - just ask anyone with a 2006 Jetta!
We also took into account failure rate and, anecdotally, it seemed that the vehicles with the 181 flywheels were failing sooner than the 126 vehicles. We concluded that, since no TDIs had start stop, the 126 flywheel was the *more correct* version, and if when we went to install a new flywheel in one of our cars here, we opted for the 126 flywheel.
All in all we recommend the 126 OVER the 181, regardless of what the VIN states, so that is why we stock and sell the 126 for all TDI applications. We've sold this version for over a decade without one instance of fitment or performance problem, so we're 100% confident that you'll have the same experience and I'd recommend you install the 126.
Sorry for being so wordy and I hope this addresses your concerns and gives you a little window into how we do things. We don't just 'sell parts' - we own these cars, work on them, and know what works and what are the best possible options for repair.
