Hydro-Gear ZT 3100, 150 hours, service done at 75 hours. Right side is much slower. Tried to adjust, no luck.

[rekit500]

Unit was working fine. I raised the front enough (using my hoist attached to the front of the frame) to change the blades, all went well. When I lowered it it started normally but went into a sharp right turn when handle were in normal position. I could go straight with the bars held offset a few inches, so I mowed a little to see if it got any better (or worse). No change. Everything looks ok as far as oil levels (mine has the two reservoirs). All I could think was air pocket? so I did the air bleed procedure but no change. Yesterday I loosened the handle adjusting screws completely for full movement and the right side is still slower than the left, quite a bit. Before all this started, at full speed this mower would blow what little hair I have back. Now when adjusted to go straight it's maybe 70% of the speed it used to go. I put a new drive belt on it several months ago, all was fine. Visually the units look identical on the outside as far as the movement of the travel from the handles to the input mechanisms. I'm in a small town and let's just say I don't think I want the local shop tearing into the drives. Serviced with Hydro Gear filters and 20-50 synthetic oil at 75 hours. Thanks in advance for any thoughts.

 

[hlw49]

You did not idfentify the mower type and model no. as that could make a difference as to what the problem is. Hustler, Big Dog, Dixie Chopper all have models that have problems breaking the Hydro mounting brackets causing the problems you are describing. Check the hydro mounting brackets.

 

[rekit500]

Thanks, here it is. Gravely ZT HD 60 model 991166 bought in 2019. Trans #ZM-GPEB-5LLF-2MRX,
#ZM-KPEB-5LLG-3MRX. KAW FR730V engine.
So the brackets that break, they are part of the trans housing or the mower frame? I'll check, but mine is residential use (2 acres) and never mistreated, I bought it new.

 

[StarTech]

On the Gravely 991166 they part of the frame and so far I have not seen any broken. One thing to check normally the movement of the drive belt idler arm as with Gravely they tend to bind up but normally affects the left side as the drive belt slips on the LH drive pulley.

Please check around about the local shops. You might be surprised. I am in a small town myself and am an authorized Hydro Gear repair shop. It may be contaminated oil die a seal allowing water into the drive but I am not personally there to check things.

Plus you should never raise the mower unless the brakes are released as these Zt-3100 uses the internal gear and a locking pawl that engages into the gear teeth,

 

[rekit500]

Good tip about the brakes. I did chock the wheels. It does go different speeds in reverse as well and I see that only a Dealer can adjust that. Do you know how involved that procedure is, I have looked online. When I changed the belt I removed the gas tank, It was easier for me that way to get it on right, but I can check that. Belt slippage should not happen on a smooth concrete drive going downhill. I checked the tire pressure, both rears at 10 lb.
When I was buying my mower there was a guy there that had left a pressure washer for repair and he needed it for his Daughters wedding day to cleanup. Picked it up and it would not even start, and he was livid, as he needed it to work like tomorrow. They just told him the tech was off that day and kinda blew the guy off. Here I am ready to drop $6K to these people. But the other places I shopped--one the wife and I walked in and the sales guys were staring at their phones. We asked for help and waited like 10 minutes looking around, no one ever came. Told the mgr and walked out. The guys were still sitting there f ing around.
I try to do everything myself. These hydros are out of warranty now. I can see them charging me $500 to tell me I need a new one. If an oil and filter change does not help I'll just run it till it don't and then buy a new one and put it in myself.

 

[StarTech]

Here is a link to the service manual that you can download; just on the download link on the Hydro Gear site.

https://www.hydro-gear.com/download/zt-2800-zt-3100-zt-3200-zt-3400/#

And to be honest most time it is just a cheap to install a new unit as Hydro Gear gives the dealers and authorized shop a six month warranty as with a rebuilt you are lucky to get a 30 day repair warranty. But don't expect much out the new warranty as they written (by lawyers) to cover the manufacture hide and not yours.

 

[7394]

Plus you should never raise the mower unless the brakes are released as these Zt-3100 uses the internal gear and a locking pawl that engages into the gear teeth,

StarTech- I drive mine up a ramp, to do underneath clean. Once at top of ramp I put the brake on, for safety..
But have not had any issues like this from OP. Mine are HG-2800, externally same as HG-3100 I believe,..