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This article will cover the repair of a Hydro Gear Transaxle 15606 320-2400R which is what is installed in my Ariens EZR 1742 (zero turn). The initial problem was the right side drive would only work with minimal load but when full power was applied forward or reverse it would not drive. The left transaxle would work fine. Upon inspection of the pulleys and belts, it was discovered the drive pulley was leaning inward toward the tension of the belt. The drive pulley attached to the input shaft had stripped the splines on both pieces.

The following will cover the procedure I used in the repair of the unit which utilizes the service manual and a little ingenuity. This does not cover a complete tear down and rebuild but a repair and general service to the unit to return it back to service.

My intentions are to hopefully help someone who may run into the same problem and help save them some frustration and maybe a few dollars. I am not responsible or liable for any problems that may arise from any individual attempting to do work on there own or anyone else's equipment as these are only techniques I utilized to repair my unit and may not reflect the exact procedures recommended by the manufacturers. No I am not a lawyer!

Lets get started. This is the Ariens that utilizes the Hydro Gear transaxle:

This tag represents the transaxle model which is the right side unit:

The first thing you need to do is raise the unit safely on jack stands. I found removing the mower deck made things a lot easier and everything more accessible. I would recommend following the manufacturer's recommendations reference disconnecting the battery and other suggestions prior to working on your unit.

The next step is to remove the rear wheels:

The next several steps involve disconnecting the various linkages and controls.

Control Arm Linkages:

Brake Lever Linkage:

Rear Brace:

Bypass Actuator Pull Rod. Unscrew the knob from the outside and pull the rod through the guide hole:

Remove the transaxle belt and tuck it up out of the way:

Using a floor jack and some scrap blocks of wood (or a transmission jack if available) lower the transaxle assembly out from under the unit:

You will need to remove the eight bolts attaching the assembly to the frame as seen in the following photos:

Now that the assembly is on the ground it was easy to see what the problem was.

The pulley assembly wobbled around, but the major issue was the input shaft was stripped as well, so there was nothing to hold onto to remove the nut. This was the reason for the decision to go inside of the transaxle to find a way to hold the shaft for the removal of the pulley nut.

To remove the transaxle from the assembly, you will need to disconnect the bypass linkage by pulling out the small hitch pins and the whole linkage assembly should slide out of the frame.

Bypass linkage connections:

Now you will need to remove the six mounting bolts:

There will be a cross brace you will want to move out of the way. You can loosen the bolt on the other transaxle and swing it out of the way:

Now that you have the unit out, you will need to drain the fluid. There is no drain plug or fill hole but you can remove the vent tube and turn the unit over in a drain pan and drain 99% of the fluid before removing the pan. There are 2 1/2 quarts of 20w50 motor oil in this particular model.

Remove vent tube:

Drain oil:

Now you can remove the ten pan bolts on the bottom. Bolt locations:

When removing the pan, use care when prying the pan off because there is no gasket, just silicone gasket sealant and you can break the edge if you are not careful! No, I didn't this time!
It was not necessary to remove the end pan for the repair. You can go crazy and tear down the whole unit for inspection if you choose, but you are on your own!

OK, the next step is not textbook, but it was what worked for me. Looking at the following picture, the white arrow is pointing at the cylinder block assembly. This is part of the pump unit. The red arrow is pointing to where there is another cylinder block assembly. Looking back at the white arrow, you can see the space between the small silver pistons in the cylinder block. These are identical to the other assembly that the red arrow is pointing at. You will need to find a small tool or item to stick in the space between the silver pistons (In the cylinder block assembly that the red arrow is pointing to) to keep it from turning because the input shaft that the stripped pulley is on is what drives that cylinder block assembly. This will require a little patience, but can be accomplished. Once you can keep the cylinder block from turning, you can remove the nut on the pulley.

Cylinder block locations. Red arrow represents hidden cylinder location:

Pulley nut:

In this case a puller may or may not be necessary to remove the stripped pulley depending on how bad the pulley has become. This one I started to use a puller but the pulley came off without resistance. Here you can see the damage to the components.

Stripped shaft splines:

Stripped pulley splines:

Now that the pulley assembly is out of the way you will need to remove the snap ring. Once this is done the whole input shaft will come out by hand. You may need to clean out the area before you start removing the shaft assembly because you do not want any dirt getting inside the unit as this will cause problems in the near future.

Snap ring:

This picture shows the complete assembly, however there is a washer and spring that will not come out with the shaft, it will fall off. If you keep the unit flat and upright they will stay in place and you can fish them out with a pair of needle nose or a small hook type tool.

Washer and spring location on the shaft:

Now that the shaft is out you will need to remove a snap ring prior to removing the bearing.

Snap ring location:

Snap ring removed:

The next step will be to remove the bearing. Any method is acceptable whether you have a shop press or a bearing puller. I used a bearing puller and it was adequate.

Using a bearing puller:

Bearing removed:

You may want to mark the direction the bearing came off to install it in the same direction although both sides appear to be the same with no tapers on either side.

Christmas! Parts were available for the entire unit, at least at the time when this article was written, from an on-line Ariens dealer. I'm not here to advertise so I will let you choose where you purchase your items.

From this point will be a reverse order of what was accomplished.

You will need to press the bearing onto the new shaft. This can be accomplished by using a shop press or a vise. I used a press and a deep well socket that just fit over the shaft and made contact with the inner race of the bearing. Make sure the socket you use does not taper on the inside and come in contact with the threads or splines on the new shaft or it may cause damage. Make sure the bearing seats against the flange on the shaft.

Bearing pressed on new shaft:

Next you need to install the snap ring.

Snap ring installed:

The next picture shows the washer and spring on the shaft to represent the position they belong on the shaft, however, you will need to install these in the unit before you insert the shaft assembly.

Washer and spring position:

First you will need to set the unit flat and in its normal upright position. Now you need to put the spring in the unit first and place the washer on top of it. You may need to move the control arm slightly to line up the swashplate so that the input shaft assembly will go into the unit. Carefully guide the shaft through the washer and spring. You should be able to visually observe the shaft going through the washer and spring before the bearing slides into the slot.

The white arrow shows the control arm and the red arrow shows the edge of the swashplate inside the unit. The washer and spring installed on the shaft will not pass by the swashplate, that is why you need to install it separately.

The blue arrow shows the swashplate lined up and the red arrow shows the spring and washer stacked and lined up in the unit awaiting the shaft.

This shows the shaft assembly installed with the bearing seated in the slot. The shaft is spring loaded now and the bearing will not seat all the way at this time.

The next step will be to install the thrust washer on the bearing.

Thrust washer:

The next step will be to install the seal. You will want to put some electrical tape on the threads to protect the seals lip. The seal will be a snug fit when you push it down into housing but will not require a special tool like a seal driver.

Seal location and electrical tape covering the threads:

The next step you will need to push the seal and input shaft assembly down to install the snap ring into its groove in the housing. Remember the input shaft assembly is spring loaded.

Snap ring installed:

The next step is to install the new pulley assembly. The new one I purchased had a slotted area on the base so I could use an adjustable wrench to hold it while I tightened the nut on the top.

Pulley assembly. White arrows show the pulley and nut. Red arrow shows the location of the slotted base to hold while tightening the top nut.

Now that this is completed you can turn the unit over and finish closing up the unit. I chose to change the filter while I was here. Its all metal and could be cleaned but it was a little crushed so I chose to change it. The old one pops off and the new one will pop on with a little help from a block of wood and a hammer. Don't hit it too hard or unevenly or you will crush your new one. Ask me how I know...

Red arrows show the filter and where the filter seats. The next picture shows the filter mounted.

Now you are ready to close up the unit. Make sure everything is clean! And nothing is left behind. Just a little dirt can plug a valve or pump opening and cause premature failure.

Unit cleaned and ready to close:

There is no gasket so you will have to use a high temp, oil resistant gasket maker like Permatex. Remember, you can use too much and if you do, the extra will squeeze into unit and could plug up the filter after time. One continuous thin bead will work just fine.

Thin bead of sealant applied:

Next, you will reinstall the ten bolts you previously removed. Make sure to clean the threads prior to installation to get an accurate torque. I am not giving torque specs as these will vary from different manufacturers to different models. Over tightening can break off a flange and cause this to be an expensive repair.

Bolts installed and torqued (Note the small amount of extruded sealant):

Next you will need to fill the unit with oil. This unit uses 2 1/2 qts of 20w50 motor oil. You can fill the unit through the vent tube hole. The manual says to fill it to @ 1 1/4" to 1 1/2" from the top of the unit. Make sure to check the level after the purging process as it will lower the level. The following steps to purge or bleed the air from this unit are what the service manual for this unit recommends.

Oil fill location:

When the unit is filled to the proper level you can now purge the unit. You will need something suitable to drive the unit at the proper RPM like a heavy duty variable speed drill that you can control the RPM or a drill press that you can control the RPM. This unit requires 1000-1500 RPM in a clockwise direction. Prior to running the unit on the bench, make sure the axle area is clear from obstructions and make sure the brake mechanism is not engaged.

Keep axle area clear.

Make sure brake is not engaged:

Drive unit in a clockwise direction at 1000-1500 RPM:

Engage the bypass:

Stroke the control lever forward for five seconds:

Stroke the control lever reverse for five seconds:

Do this three times in each direction.

Return the control lever to neutral position:

Stroke the control lever forward for five seconds:

Stroke the control lever reverse for five seconds:

Do this three times in each direction. It may be necessary to repeat these steps when you reinstall the unit.
Remember to check the oil level.

An extra set of hands would be beneficial when performing this process!

You are now ready to re-install the unit. I chose to clean the unit prior to re-assembly.

Unit cleaned up:

Re-assembly is as follows:

Place unit in transaxle assembly and line up brake lever with linkage. The blue arrow shows the brake lever location:

The white arrow shows the brake lever linkage location in the assembly:

This picture shows the mounting bolt locations:

This picture shows the cross brace location:

Now you need to slide the bypass linkage through the frame and hook up the bypass linkage to each unit and secure with the small hitch pins:

Now is a good time to go back and make sure everything is tight and secure.

Now would be a good opportunity to clean under the frame, change the main drive belt if needed check for leaks, etc.

Now you are ready to re-install the transaxle assembly. Place the unit on a jack on a block of wood or use a transmission jack if you have one and raise the assembly and install the mounting bolts.

Unit on floor jack:

Unit raised and ready to bolt in:

Install the eight bolts, four on each side. It's easier if you tighten them once they all installed.

Bolt locations left and right side:

Once they are tightened down you can remove the jack.

Next, hook up the transaxle drive belt and re-connect the linkages.

Hook up the drive belt:

Control arm linkage:

Brake linkage:

The bypass rod needs to be inserted into guide hole in the rear frame and the pull knob can be re-installed:

Re-attach the rear support:

Mount the rear wheels:

With the tractor still on the jack stands, you can start the unit and check the transaxle functions and if necessary, perform another purge on the transaxle following the previous steps discussed earlier. The only difference is you can use the bypass lever on the rear of the tractor and the hand controls to cycle the control levers.

You can also use this time to adjust the control linkages per the manufactures recommendations for creeping or other adjustment issues.

When you are satisfied with all adjustments, you are ready to take the tractor off of the jack stands and re-install the mower deck.

This should complete the repair process and get you back mowing.

References were utilized from the Ariens Service Manual available for free download in PDF form from the Ariens website. Model Number and Serial Number were required. Operators and Parts manuals are also available.

My only recommendations would be to have some type of mechanical skills or knowledge, the appropriate tools, and don't be afraid to take a lot of reference pictures or even video and some notes.

Good luck and be safe!

Originally posted on August 2012.
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