JD 644J loader I NEED HELP PLEASE!

[n bar ranch]

Hey Guys..new here and glad I found you. Here's my story. The owner of the ranch I manage brought me out a JD 644J to clean silt out of dry tanks [ponds]. It had only 2205 hrs, clean as a whistle with fresh service when it arrived. It now has 2243 hrs. I'm real easy on the machine and don't jam it around or work it hard.
I stopped to take a break today and applied the parking brake. When I was ready to go back to work it would not release.
I checked the manual and the only thing it said was if the tranny pressure dropped parking brake would automatically come on. Tranny fluid is fine. No codes show. When I press the release switch I feel the loader moved just a touch like it is released then seems something over rides it to lock up again. What else would make the brake come on and over ride the switch?
Getting service out here is pretty much impossible, 250 miles from help and the last 50 miles is gravel and rock 4x4 road so I'm kinda on my own. Any suggestions I sure would be thankful for. I really don't want to have to call the boss and tell him I broke it after just a week.

 

[tool_king]

It seem like the parking brake is loosing power or a bad ground connection.Also accumulator pressure could be dropping off.Here are some repair manuals for you .Hope fully one will help with you problem. With your serial break.Download links.

http://www.4shared.com/office/eILOaWus/644J_611232-_TM10231.html
http://www.4shared.com/office/0K0X-42H/644J_611232-_TM10246.html
http://www.4shared.com/office/C45m81AX/644J_724J_-611231_TM2075.html
http://www.4shared.com/office/xdyUEgZ5/644J_724J_-611231_TM2076.html

 

[n bar ranch]

Thanks for the info. I will study it over today and see if I come up with anything. Thanks a bunch.

 

[Sk187]

I'm sure you have fixed it by now but we had a similar problem on our 644J.

The parking brake would come on by itself while driving (dangerous) or would not come off after restarting.

It ended up being a wire grounding out by the backup alarm, which is somehow connected to the brake.

If you still have not got it fixed try opening the back door by the radiator and looking at the backup alarm wires.

I don't remember all the specifics but opening and closing the rear door rubbed the coating off a wire and it would ground out causing the brake to come on.

 

[n bar ranch]

Hey thanks for the idea! I still have not gotten it fixed. Did yours throw a code? My next step is a new TCU, I have exhausted all other options but I sure will check that wire there as soon as this dang snow storm is over.

 

[Sk187]

I don't think there was any code, the unit just always thought the parking brake was on regardless of the parking brake switch.

We had a JD dealer mechanic come out and he had seen this problem before and after eliminating the switch as the problem started looking for a wire grounding out.

If a wire grounding out is the issue I don't think it would show a code because grounding out just closes the loop like the parking brake switch would.

If it was a pressure issue for the parking brake a code would probably come up.

Post back and let me know if you found anything, seems like we had the same problem.