View Full Version : Great Dane HG hydro weak - Hydro Fluid Level?

05-31-2007, 02:28 PM
I just picked up a GD HG from an auction and got everything going pretty good, but the left hydro motor was moaning, groaning, squeeling and crying along with not pulling very well. Once the machine warms up it gets better but still not pulling really great. I had it on a very steep incline and some fluid leaked from the same hydro that I am having problems with, now it is even worse. SO - I think it may be low on fluid, but here is the challenge. The hydros are self contained and do not have a resevior that I can check the fluid level in.

So here is what I need help with.
1. how can I check the fluid level?
2a. is there a way to get more fluid in? (there is a vent tube at the top, can I try filling from there?)
2b. can you overfill the hydro?
3. what type of fluid is in there? (i see some call for specific hydraulic fluid whereas many only require 10w-30 oil)

Any and all help will be much appreciated.

Cleveland, OH

05-31-2007, 09:38 PM
i only use mobil 1 15-50 in my hydros, even when they recommend another brand, 7 years on my z master, no hydro probs., 3 month on my lesco hydro wb. oil expands when heated, overfilling will just cauz it to leak out and seek its proper level...messy if u overfill but shouldn't harm anything.mobil 1 ,amsoil, royal purple are true synthetic oils. most others can claim to be synthetic, but are actually highly refined group IV dino oils (castrol, penzoil).there should be a reservoir with a fill height indicator

05-31-2007, 11:15 PM
thanks a bunch for your reply and guidance. My Great Dane is unique in that it has self-contained and appears to be sealed hydro motors. I have read other posts that tell me that in general this design is poor and that there are many problems, but no specifics unfortunately. I have attached a link to both the Parts and Operators manual. The Operator's Manual, which I have a paper copy of is somewhat contradictory. In a few places it tells me to check the hydro fluid, but then says that I need to contact the dealer since the units are "maintenance free".

Parts Manual -

Have a super day,

05-31-2007, 11:35 PM
Your hydros appear to be HydroGear IZT units. The corect fill level is between 1 1/2 and 1 7/8 inches below the top of the fill hole. If you have a Hustler dealer close by they make a dipstick for them, PN 396242. Fill with
20w50 motor oil or 15w50 synthetic. Be sure to purge the air out of the units as that can cause the symptoms you describe also.

06-01-2007, 01:46 AM
I forgot to add, yes you do fill thru the hole that the vent tube comes out of. Unscrew the nipple and use a funnel to get the fluid in there.

06-01-2007, 10:27 AM
YOU RULE. Thanks much for the guidance. I will be working on this today and will post my results later this afternoon/evening.

06-01-2007, 05:58 PM
I filled up the left hydro through the vent tube and BINGO! I bent the clamp that was on there to loosen it up. Used some channel locks to grab the plastic vent being careful. I used my handy pocket knive to cut a hole in the top of some oil of choice 5W-30 (not sure about this part). Put a piece of aquairium air hose in the hole and squirted the oil into the vent tube until it came back out. Now I think my right hydro is jealous and wants topped off as well.

Thanks everyone! This is how it is supposed to work! Special thanks to Trae for helping support lawnsite as well.

06-02-2007, 01:20 AM
Not sure what you're doing...
You asked for the proper oil, then you put in 5w30 anyway.
You asked for the proper fill level, then just filled it til it overflowed.
Obviously it's your machine and you can do what you want, but why wouldn't you use the correct weight fluid? Also, when the hydro warms up, it will push more fluid out the vent hose as it expands. This will cover the hydro, and dirt and grass will stick to it causing a nasty mess and a potential cooling issue. Definitely look at the purging procedure and get the air out of the fluid also.

06-02-2007, 10:27 AM
Exactly, not sure what I was doing, but the guidance from you and others was what I acted on. The oil, does it really matter? I saw a fine quart of 5w-30 sitting there all alone, so I saved myself a trip to the store. Hopefully my laziness does not cost me in the end. I see your point about filling too much and making a mess, but I was very limited with accessing the hydro pump/motor. I did not want to take it off of the machine and make it a weekend project, so just filled until it was full. I will clean up the underneath after my mow today to ensure no cooling problems. I will let you know if I messed anything up with the different oil as well. Again - Thank you.

06-02-2007, 10:29 PM
does the oil matter ? of course it does....if u havent allready done it, try touching one after 15 min. of usage, u cant cauz they get so hot. your 5w30 has no vescosity and u will wear out those expensive izts..spend a little to get a lot.....get the synthetic .

06-03-2007, 10:19 AM
As Mini14 said, yes the oil does matter. I don't mean to bust your chops but I would get that oil out of there. There is a drain at the bottom of the tranny. Then refill with high quality 20w50 dino or 15w50 or 15w45 syn. When you pull the vent tube off, there will be a plastic nipple screwed into the transmission that the tube clamps to. That nipple should have a 17mm hex at its base so you can put a wrench on it to unscrew it. That will leave a large enough hole to add fluid. When you are done filling and test driving, look into the hole with a flashlight to check for bubbles. If you have bubbles, perform the purging procedures and then test and check again. The level may drop as you get the air out so be sure to check the level each time. I know it sounds tedious but if you'll go ahead and get both of your hydros serviced now it will probably be the last time you'll ever have to mess with them. And you won't be dropping $700 plus labor later on to replace one.

Good luck!