D7E steering clutch pressure low

To check if it is a supply problem or excess leakage at the clutch pistons, put a piece of thin plate under the elbows which go down into the back end case to block off flow and recheck operating pressures at the plugs in the elbows. the pressure shown will tell to if you should look at a supply problem or take out the clutches.

thanks for your reply catsilver;

The other day I checked the pressure at the pump, not at the elbows you talk about. I though the elbows would only have oil pressure if I tried to operate each steering clutch?

The machine seems to walk very slowly as well, like something is slipping - maybe the torque convertor?

Could someone give me a diagram of the oil flow from the steering clutch pump (on front RH side of torque convertor housing) I don't understand what is supposed to keep it at the 300+psi and where the oil goes when it is up to pressure.

The power-shift transmission has it's own pump on LH rear of torque convertor and the pressures seem to be ok in the 2 ports in top of the gearbox.

Sorry about so many questions

Any help would be greatly appreciated.

Thanks,
Tim.

Pump pressure at "H" should be 265-300 psi and steering clutch pistons "A & F" should be 250-285 psi.
Both readings with steering clutches disengaged and engine at low idle.

Oil pressure to the steering clutches is limited by the relief valve (item #6)

Thanks for the diagram Old Magnet, I don't have one easily to hand, I'm thinking that if pressure from both pumps is low, the common denominator is the suction screens in the bottom of the transmission case. This early model with two pumps had suction screens hidden inside the case where the suction lines bolt on. They are an absolute swine to get out, that's why no one ever cleaned them and later machines with a single pump had the square section magnetic screens in the suction lines.

Hi catsilver,
That seems like a good possibility, at least for the steering clutch pump.
As stated the other pump (separate suction) seems to be ok.

Seems to have more than one problem going on that sounds like excessive torque converter leakage, upset valving or scavenge pump not keeping up.

Needs to check scavenge pump screen also.

What are the pressure readings for the transmission pump and the two port readings on the transmission?

Pump pressure at "H" should be 265-300 psi and steering clutch pistons "A & F" should be 250-285 psi.
Both readings with steering clutches disengaged and engine at low idle.

Oil pressure to the steering clutches is limited by the relief valve (item #6)

[quote="Old Magnet"]Pump pressure at "H" should be 265-300 psi and steering clutch pistons "A & F" should be 250-285 psi.
Both readings with steering clutches disengaged and engine at low idle.

Oil pressure to the steering clutches is limited by the relief valve (item #6)[/quote]



Thanks for all your reply's

pump pressure at H was about 180psi

Maybe I don't understand - you say check with steering clutches disengaged - I just had it running at idle, not touching the steering clutches.

Item no. 6 relief valve - i removed a relief valve (1 1/2inch spanner) that comes out of the valve pointing to the Lh side of the machine - it was stuck shut - had to drive valve apart and free it up.

This steering clutch pump doesn't seem to have a strainer in the transmission - just a magnetic one under the pump
The transmission oil pump has a cone type strainer - fairly clean except a few pieces of brass shavings.

I have tried pressure at port 'G' in top of transmission - was about 280psi

hope you can keep trying to help!

thanks again,
Tim.

Hello Tim, You check streering clutch pressure at A and F with the clutches pulled back, if the pressure is low, block the elbows as described before and check again, this will confirm if any problem is a control fault or seal leakage in the back-end.
Checking the lube valve pressure (C) will tell you if there is enough pump flow kept the converter and oil cooler fed.

Hello Tim, You check streering clutch pressure at A and F with the clutches pulled back, if the pressure is low, block the elbows as described before and check again, this will confirm if any problem is a control fault or seal leakage in the back-end.
Checking the lube valve pressure (C) will tell you if there is enough pump flow kept the converter and oil cooler fed.