Tuff-Torq Transmission Leak Repair
The oil leaked out of the hydrostatic transmission on my Cub Cadet LTX 1045 riding mower. The mower was new in 2014, and has serial number 13WX93AT###. The transmission is K461A6460-######. The axle shafts are ¾ inch and the oil seal outer diameter is 1.25 inch. Seepage from both axle oil seals eventually drained so much oil that the tractor would barely move. There was no practical cure for this because the Tuff-Torque transmission had no means to refill it. There is no drain or refill plug in the entire unit. Apparently the designers intended the initial oil fill to last the tractor’s lifetime. That’s a pipedream. The axles, both of them, are low in the oil reservoir and have solid bushing bearings near the outer ends. These are sealed with a simple standard-looking oil seal. One pressed into place, made of neoprene-like material and with a conventional spring under a sharp edged lip. That rides directly on the axle and in tractor service you can be sure it will seep, and eventually, seep a lot. There are no springs, the tractor rides rough and there’s plenty of bouncing weight to strain these axles off center and wiggle the oil seal. In addition, my tractor had small funnel-shaped plastic axle shaft covers between the outer wheel and inner transmission housing. Possibly they are to keep dirt and grass away from the oil seal area; or maybe they’re just decorative. Who knows? But the net final effect of them for me was to trap moisture at the axle shaft just outside and right up against the oil seal, itself. Result? Significant rust at the location of the oil seal on the axle shafts. These are otherwise finely machined or polished in a way that enables the oil seals to work pretty well initially. But the oxidized surface, even when smoothed by use, destroys the oil seal. There was an early recall with one seal that I know of replaced. It did not reduce the problem and both ax;es leaked slowly. In late fall 2016 this accelerated. In early spring 2017 the tractor was unusable.
Oil seals are inexpensive and available on line. Be sure to get the correct parts for your unit. There seem to have been several different hydrostatic transmissions supplied in these mowers. Replace these before the work below. Remove the wheels, the old oil seals and rust on the axle shafts. (Removing the wheels was complicated by dense white thread locker of some kind. I used an impact wrench and broke the head off of a class 5 hardened bolt. Gentle heat from a propane torch easily softens the thread locker.) Use a rust reconditioner and very fine abrasive paper…I say 800 grit or finer. The smoothed axles and new seals need to be in place to perform the final steps. The complete fix, however, is somewhat more involved than this alone.
To refill the transmission I did this: Remove it from the tractor. That means battery out, mower deck off, Fan and belt off, 5 mount bolts out, 2 control rods and one cable spring removed, and a Molex wire mount disconnected. Wheels still off.
Then place the transmission upside down in a big drain pan. It needs to be well positioned and leveled in a way that allows the work without moving off level. Remove the bottom panel from the transmission. The seal is black gasket RTV material. Clean this from the cover and the transmission without scratching or marring the surface. I found the transmission well done on the inside with sharp spur gears and well done looking parts. Substantial oil remained in the unit. I read somewhere that it is 20-50 motor oil. Refill the open transmission almost to the seal surface. (My unit took about a quart and one half altogether.) While the bottom plate is off you can drill and tap a hole in it to drain and refresh oil in the future. See the photos. There is a boss in the casting with a deep cast hole in it that appears to have been for a drain tap. I drilled and tapped this for a ¾ inch long 5/16 – 24 thread bolt. Be sure to make an oil seal gasket. Yes, this is on the bottom and very small, so using it in the future to refill the transmission will not be convenient, just somewhat easier than removing the bottom plate again. Place new sealing black gasket type RTV sealant on the clean bottom plate edge and transmission. Reassemble the plate and transmission finger tight and let cure overnight. Follow the sealer’s directions to get full curing. Tighten up, use the new hole to fully fill the transmission and reassemble the whole mower. It should then work perfectly. How long the new oil seals will work properly is an unknown roll of the dice. A month later mine is doing fine so far.
The basic transmission looked fine inside and one could probably invert it, let all the parts come out, and maybe find a suitable refill hole spot somewhere on the top. I did not want to chance this complete disassembly and the fix above does not require removal of any interior components. The drilled boss location is clear of all interior elements and is an easy modification.
Good Luck!, RanchoDeluxe
