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PK., Small Engine Technician
Category: Small Engine
Satisfied Customers: 1052
Experience:  Retired Owner of a full service shop and national parts sales website.
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i have a cub cadet rzt 50, the left transmisson quits pulling

Resolved Question:

i have a cub cadet rzt 50, the left transmisson quits pulling after 45 minutes of mowing changed the oil and purgered it what could be the problem??????????/
Submitted: 7 years ago.
Category: Small Engine
Expert:  PK. replied 7 years ago.
Did this begin before or after the oil change? What oil did you use to refill with?

Is the transaxle clean and the fan in good condition? And, about how many hours are on the unit? Thanks, PK.
Customer: replied 7 years ago.
its got 88 hrs on it . before the oil change , 20/50 gtx the fan is brand new ,
Expert:  PK. replied 7 years ago.

Will it pull in reverse after the forward drops out? The first thing we always do is purge the transaxle again and re-check the fluid level. When you purged it the first time, did it need more fluid after purging?


The most common cause of this would be fluid failure after it heats up. The fluid boils and hydraulic pressure is lost. You could be losing the piston seal in the pump or motor due to distortion or galling, but the fluid would be more likely.


I don't see a reservoir or external filter set-up for the RZT50. You don't have one do you? Also, what's the model number of the mower? Is the terrain this is used on very hilly?

Customer: replied 7 years ago.
no hills , it want pull or go in reverse either , just a little bit after purging the first time , what kind of oil wuld be the best 17aa5d7p is the model number
Expert:  PK. replied 7 years ago.

We use Castrol and have great success with it. You have the Kawasaki engine? That was a good choice.


I'd try purging once again and rechecking the level. Was the old fluid burnt or discolored?

Customer: replied 7 years ago.
it was just white like it had air in it ????? but how did air get in there from never touching it the first time?    
Expert:  PK. replied 7 years ago.

The only place the fluid is pressurized is between the pump and motor, the transaxle itself isn't sealed air tight.


But it shouldn't have been white. Are you sure it wasn't water mixed in?

Customer: replied 7 years ago.
the secound time i changed it it was the same way whitest looking but not the water in oil look
Expert:  PK. replied 7 years ago.
If it's foaming, then I would have to think it's either the pump or motor pistons not sealing. Is this not still under warranty?
Customer: replied 7 years ago.
naw it just had a two year warr.    how could you check them?//
Expert:  PK. replied 7 years ago.

It has to be disassembled. You really need the Hydro-Gear manual for the transaxle to do this and they don't let them out to the public as far as I know.


The fact that the oil is foaming is what's causing your problem with the pulling. Now the hard part is finding why it's foaming. The only thing I can think of that's likely to cause that would be a problem in the center section, either the pistons or the section itself having a leak.


After looking at the schematic again, it might be possible for the bypass valve to be causing this. This valve is the one which you engage and disengage to freewheel the mower. If it's working loose, it could cause the oil to aerate, and you would also lose power. The valve itself requires disassembly of the case to access.

Customer: replied 7 years ago.
i got a break down manuel , but it dont tell me how to check the piston on the motor, or the pump
Expert:  PK. replied 7 years ago.

You have to have the service manual for teardown and for checking all the clearances. You can contact Hydro-Gear and see if they will provide one. You'll need the model and serial number from the transaxle itself before contacting them. Hydro-Gear doesn't allow it's Service Centers to give out this sort of thing and their website with the manuals is password XXXXX anyway so I can't give you a link to it.


To contact Hydro-Gear you can go to their website at


They're not terribly complicated. If you can rebuild an engine you can rebuild a hydrostat. They are a bit more clearance critical than an engine though.



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