Tech Tips – Residential IHT (w/ integrated reservoir tank) Oil Maintenance

Tuff Torq Oil Service Procedure for Residential IHT  units with Internal Reservoir Tank

Models covered by this procedure:

  • K46 Series
    • Manufacturing ID: K46AA, K46AC, K46AG K46AW, K46BA, K46BC, K46BE, K46BL, K46BM, K46BN, K46BP, K46BR, K46BT, K46C, K46CJ, K4CR, K46CW, K46HD, K46V, K46Z
  • K57 Series
    • Manufacturing ID: K57A & K57F
  • T40A & T40J

Normally the model K46 & T40A transaxles, that are featured in many tractor and rider models, do not require any servicing for the life of the vehicle. If checking the oil level/condition, it may be necessary to remove the transaxle from the vehicle.  This is necessary to access the fill port (black cap) located under the pulley and fan (see diagram below).

After removing the unit from the vehicle, place the transaxle on a level surface and remove the fan and pulley. Then remove the black cap shown in the diagram below.  Maintain the oil level at 20~25 mm (3/4”~1”) below the lip of (black cap) port (see diagram below).

Technical note: Check oil level when oil is at room temperature (20°C or 68° F) and the unit case is level and secure.

Always use the fill port (under the black cap) to drain the oil from your Tuff Torq unit. Do this by removing the cap and inverting transaxle.

Tuff Torq recommends using only using approved Tuff Tech drive fluid when servicing any of our transaxles.  Only use the fill port (covered by the black cap) to refill unit. You will need approximately 2.2 liters of oil to properly refill the unit if completely empty. The amount of oil needed may vary for your service, due to the amount of residual oil remaining in case after draining and the condition/age of the unit you are servicing.

While reinstalling the fan & pulley be sure to place all components on the drive shaft in the reverse order from which they were removed and verify proper torque for each bolt.

Tuff Torq Oil Service Procecdure Diagram

Tuff Torq Oil Service Procecdure Diagram

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  • Carl Ewing says:
    Your comment is awaiting moderation.

    Following the recommended oil change procedure I’ve noticed that when the drive shaft at the top is being turned. clockwise on my K46AC, and the freewheel lever is disengaged I can grasp the turning portion of the axle (right side) and it simply stops in my hand. Is this normal?

  • Ben says:

    Could I replace a K46BC with a K56? Are they the same size, with the same mounting points?

    • ggraham says:

      These transmissions are built specifically for the tractors that they are in and swapping can cause all kinds of unforeseen issue. The K56 is a very different transmission than the K46 and no they will not interchange without major modifications.

  • William Black says:

    My shop was flooded in Hurricane Harvey. I am afraid water got into the transaxle. The top of the Tuff Torq was under about 8 ” water. Should I split it apart or just drain and put new oil?

  • Javier ibarra says:

    How do you remove the black cap seems to be stuck on? I am trying to refill the fluid because it has been leaking a little bit

  • mike russell says:

    what are the differences between a k46 and a k46ac

    • Hello Mr. Russell. Thanks for your message. While I am happy to help any way I can, you have several questions here that would be best answers by one of our service professionals. You can reach them at or toll-free at (866) 572-3441. The short answer is the “AC” designation describes a particular control logic and specific design set defined by a particular OEM for their tractor application. If you contact our professional service team, they will be able to look up and help you understand the features and specifications of the K46AC model. Hope that is helpful, have a great day!

  • Erki Potisepp says:

    I have Ariens 46″ Lawn & Garden Tractor, 22hp B&S and i would like to change the hand gear to pedal gear (using Husqvarna YTH 20K46 parts)
    I have a question about K46 hydrostatic transmission. Whate are the main differences between K46ba (Ariens) and K46bt (husqvarna) hydrostatic transmissions. Does theoreticaly hand transmission connections fits with pedal transmission parts?

    • Hello Mr. Potisepp. There are several differences that can be designed into each K46 unit Tuff Torq manufacturers for an OEM. The main issue with using non-original parts in a repair is the danger of the non-original unit not having the same “control logic” as the original unit. Meaning, Tuff Torq has the ability to set up a transaxle to have forward/reverse initialized by the control arm in either the “push” or “pull” directions (depending on the need of a specific OEM). Using a transaxle from another OEM may create a situation where initializing your tractor in the forward direction would cause it to actually go backward, and vice versa. So, we do not recommend replacing units with transaxles designed for other vehicles. For more information, I recommend you contact our service team at or give them a call toll-free at +1 (866) 572-3441. Hope this was helpful! Have a great day.

  • I have a tuff Torque K72 High speed transmission, and I would like to know if there is a service manual for this unit that I can get to better help be keep it maintained properly.? It’s in a 2017 Simplicity Prestige tractor. The owners manual that comes with tractor doesn’t cover good technical maintenance.
    Thanks for any info you can give me.

    • Hello Mr. Kraus. I’d recommend you contact our service department. They will be better equipped to find you the information you need to keep your K72 unit working at peak performance. You can reach them via email at or toll-free at +1 (866) 572-3441. Have a great day!

  • Michael Lacy says:

    Wanting to know what the cost of a pump and motor for my K46 transmission would be. I’m doing a rebuild on it as the mower would not move in forward or reverse.

    • Hello Michael,

      Since each model of our K46 transaxles is unique in its specifications outlined by the OEM, it’s probably best that you contact one of our service technicians with your specific model information. They will be happy to assist you with your request. Please feel free to contact them at (866) 572-3441 or via email at Thanks!

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