I have a GT235, removed the two plugs, drained about a gallon and had the same issue. I found that waiting 30 seconds or 30 minutes wasn't really enough. I was adding fluid for the next few cuts until what I assume is that all the air worked out of the system. Out of curiosity, I called the JD dealer to find out if the manual had left out some type of bleeding process. The service manager indicated they propped up the real axle and went through a procedure to run the transmission forward and reverse to alleviate that issue. He said the process is available in the service manual. I have not needed to change the oil since then but may try to obtain that manual when I do.

You will be better off if you follow the above advice about raising the rear axle off the ground so there is no actual loading of the pump and motor inside the axle.

wheely boy...

FYI the picture and the air purge procedure @

https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/ttcoil/pdfs/AIR%20PURGING%20PROCEEDURES%20FOR%20HYDROSTATIC%20TRANSAXLES.pdf

Thanks for the responses. I followed the proceedure in the service manual. It is similar to the proceedure offered by Tuff-torq except JD does not mention anything about operating the bypass valve. Im not sure how to do that anyways since in order to run the engine I have to be in the seat unless I set the parking brake which draws in the bypass valve. Anyways, I thought you weren't supposed to operate the bypass valve with the engine running. Either way, the oil level didn't budge.

The manual says not to add oil to the gear compartment port shown in the photo above. If I were to try to add oil to that port, is it the same hydro oil that I added to the other one?

Also, both the service manual and the Tuff-torq instructions seem to imply that this purging is done when the transmission doesn't move. Mine seems to operate except with only half the oil.

Normally I am not intimidated by doing things like this to my tractor, especially when I have instructions. In this situation I am starting to wonder if taking this on was a huge mistake since the instructions provided seem to be lacking.

Follow what TT says.

Cinder block on the seat works great for operating the hydro when wheels are off the ground

Purge is absolutely required when you drain and refill cause what's in the trans after draining?... AIR.

You may find that after an hour or so of operation that your trans BURPS an air bubble and the level is low so keep an eye out for that.

You also need to be careful cause some K71 version take Hi-Vis and some take Low-Vis. Whichever is correct for your K71 is used in both sides of the trans.

https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/ttcoil/pdfs/Fluids%20and%20Lubricants.pdf

So am I supposed to add oil to both sides of the transmission? I drained oil out of both sides of the transmission. We are talking about a half-gallon burp here.

Problem solved. During the last week the oil level dropped only .25 quart. I went to the dealer and was able to speak with a mechanic. The gear compartment fill port (the manual says to not remove this) needs to be removed. This allows the air to bleed out. I had the other 2+ quarts in in under a 1/2 hour.

"Follow what TT says"