JD 300B Hydraulic pressure problems

[cliffj59]

I would think that the high pressure side and the low pressure transmission side are two diffrent systems. So why does the pressure drop on the transmission side when I move the FEL control valve?

 

[Tx Jim]

Because trans pump(low side) must supply oil to high side so high side oil demand causes low side pressure to drop.

 

[cliffj59]

I have replaced the seals we have mentioned in this post and still have the same pressure drop when operating the FEL. Is there somewhere to bleed the air out the hyd system?

 

[cliffj59]

How do I chaeck the suction screen on the transmission?

 

[Tx Jim]

One needs to drain trans oil or insert a running shop vacuum nozzle in hyd filler hole with shop towel blocking remainder of opening. Remove plug & pull screen for inspection. I'd advise to check hyd filter relief valve(also in photo) to be sure it's not stuck open.

 

[cliffj59]

One needs to drain trans oil or insert a running shop vacuum nozzle in hyd filler hole with shop towel blocking remainder of opening. Remove plug & pull screen for inspection. I'd advise to check hyd filter relief valve(also in photo) to be sure it's not stuck open.

Well mine don't have a screen in it, that's the hole I drained the fluid out of and didn't see any screen I will get one installed. The good news is that with the seals on the rockshaft piston I replaced now when I operate the FEL with the 3 point raised up the 3 point dosn't drop any so they are holding pressure. I can look into the filler hole and don't see any fluid spraying or dripping.The pressure still drops on the test gauge when operating the FEL from 130 down to around 50. So I will check out the hyd filter relief valve next to see if its stuck open, Thanks Tx Jim

 

[Tx Jim]

You're very welcome. Are you positive there was no screen? Sometimes the screen can be difficult to see.

 

[cliffj59]

You're very welcome. Are you positive there was no screen? Sometimes the screen can be difficult to see.

The fluid ran out of the hole quickly and I stuck my finger in there but didn't feel anything.