Small Engines (Lawn Mowers, etc.): Cub Cadet Zero Turn, cub cadet zero turn, purge unit

Question
QUESTION: Hello, I have a 2006 Cub Cadet RZT-42 that I bought used. It runs and works great but after about 45 minutes the left hydro slows down and does not want to move evenly with the right so it wants to go left. After it sits and cools down it will run fine for about another 30 minutes and the cycle repeats. I called the dealer and he said it sounded like the hydralic fluid was breaking down and to drain it and put 15W-50 Mobil 1 in it. Any advice would be helpful. Thanks Jim

ANSWER: hi jim

be sure that the drive been transmitted is equal to both  hydro units  
with no splipage and check that trans cooling fins are clean and the exterior of both trans are clean & dry and have no oil seeping out   if oil can get out , dirt / air can get in.  

yes  it does sound like the oil in the hydro unit needs changing, its dropped its additive pack and been getting hot and quite possibly been getting air entrained in it - cavitation comes into play as well- when this happens  unit can do things like  you have said  and can be noisy and seems to have no power

remembering flow relates to speed and pressure relates to torque in a hydraulic system

you should find a drain bolt on those trans units to drain oil  , then refill with correct type and quantity of oil  - purge unit of air and recheck  oil level  - follow manfacturers recommendations  

note do both units at same time

let me know what you find


here is web site to help with parts

http://www.partstree.com/parts/?lc=cub_cadet&mh=15

cheers hope this helps

paul






---------- FOLLOW-UP ----------

QUESTION: Paul, thank you so much for your response. My service manual that I downloaded on this mower says the transmissions are sealed units. I cannot find a drain plug at all. There is an oil reservoir under the seat and it is filled to where it need to be. Any Idea on how to change that hydraulic oil? My model # is 17BA5A4G710.

Thanks for all!!

Jim

Answer
hi jim


got your message

just looking into something at the moment and waiting for a reply

cheers  will send more info when i recieve an answer

hi jim  

asked fellow tech  on this matter  his advise was about the same as mine
and looks like will be some work,  but will pay off  units are hydro gear
318-2200L  (oem 618-04432)left hand unit ----- and 318-2200R  ( oem 618 04431)right hand  unit )

make a note of all  connections  and do not open or loosen any cover / casing bolts
only remove oil fill plug / and or  oil resivuoir hose  to drain  tank ( keep any dirt from entering system )

remove the left hand trans unit from tractor - drain the oil from the oil fill hole on the top side right above and in line with the axles ( you will see the rubber plug) this is oil fill hole , drain unit from these holes ,  let gravity do its work  ( make sure to prop up properly )
and leave overnight to drain out completely ) note  do the other unit as well as good practice  
reinstall both and refill with required amounts and also  drain resivuoir  and refill that as well if need -

use  20w/50 oil    amount  of oil   54 - 57 ounces  ( 1.53 litre  to 1.68 litre )

purge proceedure -:  raise up rear end off ground and engage bypass  on trans unit  start and run engine at 1/2 throttle  - stroke the fwd/ rev pedal fwd  4 or 5 times for about 30 seconds each time   then  rev  4 or 5 times  then disengage bypass on each box  and repeat again  

repeat this proceedure for other unit   note purging can take a while

all going well  units should drive wheels with no noise or cavaitation  

jim its alot of work  but it needs to be done , oil is cheaper than new trans units
from the damage cavitation can do

cheers  paul