Brakes won’t release on 770 John Deere grader

[Da newfie]

parked a 770 jd grader last fall and now she won’t go in gear because the parking brake won’t release. Any help would be greatly appreciated. Thanks in advance

 

[seville009]

Hammer on the brakes to break up the corrosion bond possibly.

 

[Tx Jim]

Welcome to TBN
My inexperienced guess concerning JD industrial equipment tells me you probably have a parking brake control cable that needs lubrication such as PBBlaster, Kroil or similar penetrating fluid

 

[mini14]

I had to hammer drum brakes on a customer's Honda civic and it was only parked over the weekend.

 

[ovrszd]

His brakes are internal, oil bathed.

The park brake is electric over hydraulic.

To set the brake hydraulic pressure is released. This is logical so it doesn't slowly release after the machine is parked.

To release the brake hydraulic pressure is applied. This is accomplished with an electronic actuated solenoid.

I'm guessing you have lost electric power to the solenoid. Or the solenoid has failed.

Find the solenoid and check the circuit for power when the "key" is on. If no power, search for a fuse?

If the circuit powers up when the key is turned on then the problem is more than likely the solenoid.

Report back with your findings. Hope it's a simple fuse.

I've ran JD graders since 1989. Now running a JD 672G.

Welcome to TBN.

 

[Tx Jim]

ovrszd
I see nothing electrical in the parts schematic for 770 parking brake. It appears cable controlled to me.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/63197/referrer/navigation/pgId/35619

https://partscatalog.deere.com/jdrc/navigation/equipment/63197/level/3/snp/MTA0NjU2OkNIQVBURVJbMTA2MTojQlVTSU5FU1NfUkVHSU9OLDI1NTY6I0NBVE

 

[ovrszd]

ovrszd
I see nothing electrical in the parts schematic for 770 parking brake. It appears cable controlled to me.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/63197/referrer/navigation/pgId/35619

https://partscatalog.deere.com/jdrc/navigation/equipment/63197/level/3/snp/MTA0NjU2OkNIQVBURVJbMTA2MTojQlVTSU5FU1NfUkVHSU9OLDI1NTY6I0NBVE

The 770 JD grader has been built over a span of 35-ish years. There are many model variations. I've operated 6 of those variations. The B version used a hand brake. Everything built since 1993-ish has been electric over hydraulic.

Since the OP didn't specify which model he's working on I simply assumed it was newer than 30 years old. If I'm mistaken I'm sorry.

If it's the older cable version make sure the actuating lever at the trans case is releasing.

 

[ovrszd]

In reviewing TxJim's link. If it's that version the park brake has nothing to do with the trans not going into gear. This system uses a caliper on a spinning disc outside the trans. All it does is stop the trans from turning.

The later cable version uses the parking brake integrated internally in the trans. It will lock out the trans ability to go into gear. The more later versions used electric over hydraulic and also lock out the trans.

 

[Tx Jim]

ovrszd
Thanks for your explanation. I failed to locate another style parking brake control in the only JD parts catalog #1504 for 770. As I previously stated my experience with JD industrial tractors/implements is very limited

 

[ovrszd]

No worries. To get a complete listing of JD grader models search "Construction" equipment rather than AG.