I have a cub cadet model 21ab455c756 tiller. Worked fine when put away 3mos ago. Today... tines appear locked up. Wont turn. Gear selector lever clicks freely thru the different speeds/options. When trying to engage the drive.... it kills the engine because of locked up tines. Suggestions?

Hi, I'm Peter I would first tilt the tiller up and put some kind of blocking up it to hold the rear end up so you can access the tines. It sounds like you may have debris, vines, string, wire, etc wraped up around and in your tines. This is very common and the best way I have found to remove this mess is with a good pair of side cutters, ( Dikes ) and a pair of needle nose and pliers to grab the bits and pieces as you cut them out. Becareful not to let the tiller fall on you or your hand slip hitting the tines or other sharp metal and wire that may be in the mess. If once all that is cleared and you still are having problems then I will post this from one of my previous post. I hope it isn't this serious as it sounds like you have a new tiller. If not and it's second hand then this added information may be helpful.
Hi I'm Peter. I realize this is an old post but I will answer it anyway for anyone that has the same question. I just finished rebuilding a Cub Cadet RT 65 Transmission. There are a couple of problems you may be facing. First the shifting shaft that goes down into the transmission is not sealed verywell so my understanding is that water from rain or washing the unit may run down into transmission. and may rust up some parts. You can try spraying penetrating oil and moving it back and forth and you may free it up. I am doubtful though but it's worth a try. The shaft has an arm with a little shaft on it that slides in the grove of a shifting yoke. The shift yoke is mounted on a shaft that has detent groves in it. The yoke has a stiff spring and ball in it that when you shift the transmission it slides up and down to the various groves of which each is either neutral or one of the drive or drive and tiller engagement positions. If your unit is like a few I've seen they have been packed with grease and the little ball and spring cannot get lubrication so they wind up freazing up makeing it near or impossible to move the yoke up and down which fits around the shaft of the primary shift gears that move up and down with the yoke. As they move up and down they will engage the transmission the the various modes of travel and operation. There are other problems also as several of the gears in the transmission have needle bearings so if your unit has only grease in it and not a type of gear oil the needle bearings have no way for the grease to get to them so they destroy themselves which may lead to a catistrphic failure which may include gear teeth being broken off and locking up the transmission. Needless to say the transmission case will have to be split and all new bearings installed plus replacing any other damaged gears, chains, , etc. You can order the bearings from multiple places Cub Cadet of course or you may do as I did and go to Mader bearing or what ever local bearing supply shop in your area and buy new ones. Remember take the old ones with you so they can match up the ones for your particular unit. I can tell you some of the parts/gears are used in most of the same size tillers of nearly all of the major brands. Yep Troybilt, Cub Cadet, Ryobi, Craftsman so there may be minor differences but I'm beginning to suspect as with a lot of appliances today that there is one company that builds them and sells them to the different Name Brands to put their logos on or either they just get their parts from the same place. LOL. There are a couple of videos on you tube that a fellow has taken his apart and filled it with grease. I haven't found it yet in my manuals but from all my years as a mechanic most transmissions have some type of gear oil in them and not grease hence the needle bearing getting destroyed.. I have read references that say that the Cub Cadets at Tractor Supply come with oil in them then people have said they read to put grease in the transmissions when they get low on oil because a seal leaked. What ever ! I say replace the seal and make the necessary changes if any need to be made so that you can run gear oil in them. The oil can reach the needle bearings and give them a longer life as the grease is unable to reach them. There are several sources I believe even Cub Cadet offers a free download of the Owners Manual and a parts manual with a breakdown of the transmission including parts numbers.I replaced all the seals and bearings in mine for maybe $60 and a gear that is universal to all of the tillers for around $80. Prices can vary a lot so shop around. The same gear can be had from $ 79.99 - $ 129.00. They even all use the same parts number between the major brands. The drawing in the parts Manual is very confusing so to help everyone out I put a video on you tube Cub Cadet RT 65 Tiller where I have a cleaned transmission with all the gears in the case and I take the out, show you their positions, explain the operation of the transmission and then show how to assemble the gears in their proper place. I also explain and show the detent shaft and shifting yoke operation. The link ishttps://www.youtube.com/watch?v=GVgOPCRpc5o&t=1sPlease like and subscribe so I can put some more videos up to help more people. Comments and questions are always welcome. Hope this helps Peter
Cub Cadet RT 65 Tiller