yes the engines between the 2 can be swapped reguardless of what tranny is in them . As for the last question about the mower that wont stay running , check the gas cap vent hole and clean it out with a paper clip or sewing needle next check fuel filter make sure its not plugged and id the correct one there are 2 different kinds one is small with just a screen for non fuel pump mowers the other is a little bigger and clear and you can see a cone shaped filter media in it that is for engines with a fuel pump and if used on a engine with out a pump will cause fuel starvation and stalling , check for fuel leaks also and if equiped check the fuel pump after those things if everything is ok then it may be time to pull the carb off and clean/rebuild it

Thanks to this Thread I was able to repair the LT180 I just bought at an auction. All was good until about 30 minutes of mowing when the world stopped turning and the machine was barely moving. After reading all the info above I took a slightly different approach to remedy the slow trans-axle condition. Taking the least aggressive path, I was curious if just a fluid change would make a difference, I decided to jack the rear end up and pop a couple drain holes into the Axle cast housing where Tuff-Torq suggests. Here is a Link https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/ttcoil/pdfs/K46%20Drain%20Port%20Location.pdf I used a 1/8 stubby drill as not to injure any interior components, both holes drained over night. I then added 2 self tapping screws 1/2 inch long with a neoprene washer. Without the deck on the machine I was able to reach under the frame and pop the fill hole cover off using a stubby flat screwdriver. I cleaned up the magnet and filled the unit. 24 inches of 3/8 clear tubing and a small funnel allowed me to add back the 2 quarts of cheap 10-30 oil for my test. Popped the magnet and cap back in place and DONE! I am pleased that the result was success, the machine runs very well without growling and slowing after 30 minutes of use. My intention is to replace the 2 small drain holes with real drain plugs after about 5 hours of use and refill the unit with synthetic oil for hopefully many more years of use. Happy Mowing!!

You can go to Tuff Torq's web site and take a look at the diagram for your tranny. I think the part you are talking about is the tranny vent, but on the K46 it may also be the oil filler hole as well. My K51 has this same plug, but it is separate from another big cap where the oil goes in. When I emailed Tuff Torq they sent me a quick reply (next day) which included instructions and pictures on how to change the oil on my unit. They also confirmed it was OK to use synthetic oil as a replacement. The recommended oil weight for my tranny was 5w50. Mobil1 is not available in this weight, but Castrol Syntech is and that is what I used. http://www.tufftorqservices.com/cgi-bin/tts.storefront

I just finished tearing the old one down, I believe it is salvageable. There is a lot of rust inside of it, but I think I can bead-blast it all off. Maybe I can braze the case and save it, too. Anywhere on the net I can find a repair manual on these transaxles? Looks to be a pretty stout unit, just can't figure out what cracked the case? Maybe water got in it and froze??