I have a 2017 Mustang gt manual transmission. My car was flooded so water got into the transmission. I want to do a Machine flush but I need about 12 qts. To do a thorough flush. Dealership says the transmission oil I need is motorcraft xt-11-qdc but it's 30$ a quart. What other oil can I use to at least flush it so I can add the xt-11-qdc after

 

I've use Pennzoil Synchromesh in my original TR3650 and my T56 Magnum XL (very similar to the transmission they used in the Viper and GT500), both with great results. I assume it's safe to use in the 2017 but might not hurt to check

 

I did some googling about. Here's what I've found.

The MT82 in the pre-15 cars isn't the same(??) as the ones in the 15s and up. As such, there was some cold shift issues with the new ones. Ford stopped using their Mercon LV with the XL-18 friction modifier and went straight to the QDC fluid to stop this problem. And the results are mixed. But that's why the QDC is being called for by Ford in this case, and in all MT-82s going forward, near as I can tell.

People have been all over the map, just like the '05-'10 TR-3650 issues. Royal Purple Synchromax, Pennzoil/GM Synchromesh, go back to Mercon LV + XL-18, stick with QDC but add the XL-18 too, Amsoil Severe 75w-90, Redline ATF, Mobil 1 ATF.... Basically most manual transmission/Mercon V equivalent ATF fluids are all in play, seems, and everyone has their 'no, this one is the BEST, I swear!' on it. Meaning none of them are. Which is what I've found with the TR3650 overall, but I'll be stickin' with the Mobil 1 after trying RP Synchromax and the Pennzoil/GM Synchromesh, it does seem to work well in my case. *My* case, mind...

So all that to say this: If you're gonna flush it, I'd probably just get some cheap Mercon LV equivalent, do the flush, then throw the QDC+XL-18 in it and see how it likes that.

Hope that helps. Good dang luck to ya! And welcome to the forums!