MCV Issues

I posted some issues I am having with my 706 back around July 4th.
When going down the road and coming to an intersection and you dis-engage the clutch and re-engage without coming to a complete stop the tractor will coast then jerk and take off again. But if you apply the brakes a little, the tractor will take right off.
I replaced the clutch a short time ago, when I put the tractor back together I did not force anything. We rolled it back together and tightened the bolts, but nothing was pulled together.
I did replace the brake valve with one from a salvage yard. I was told the replacement came from a 766, but that these valves are interchangeable?
I checked the pressure on the MCV and I get no pressure on the sensor port with the clutch in or out and tractor running ¾ throttle. I even drove it done the drive and no pressure ever shows on the gage. The gage is 0-100 in 10 pound graduations. I also tried to adjust the MCV linkage with the clutch disengaged to get pressure but get nothing no matter where the linkage is.
I also changed the filter for the hydraulic, but the new one went back in the same as the old one came out.
My steering, brakes, and other hydraulic work fine as far as I can tell?
I checked the pressure at the bottom of the MCV and I get 200 PSI steady .
Any thoughts or suggestion to check or try?
Thanks for your time and consideration.

It has a "TA", right?

The hitch and auxiliary valves have a different hydraulic pump than the steering, brakes, and TA so we can leave them out of the discussion here.

You have an interesting set of circumstances. Why was the brake valve changed? Were thing working OK before the clutch was replaced? Was the MCV removed when the clutch was replaced?

The brakes valves are different between the 706 and 766 but the newer one should work better in the 706. The original valves were open center style and bleed off 1 GPM of the oil flow from the MCV whether or not the brakes are not being used. The valve for the 766 should be a closed center valve and will only allow 1 GPM flow when the brakes are being applied. That should give you 50% more flow for the TA controls and TA lube.

The 200 PSI for the MCV pressure is a little low. You did not say but does that pressure rise when the brakes are applied? I would guess that it does since it makes the TA respond differently. You should see a reading between 230 and 250 for low pressure and between 250 and 280 for the high pressure. The pressure should be high when the TA lever is in either TA or DD position and drop 20 PSI when shifting half way between the two positions. Do you see a pressure drop when shifting the TA? Doing the testing is probably the only time you want to shift the TA slowly.

My first guess, only it was apart , is a problem with the brakes valve leaking enough flow that the pressure regulator valve never reaches the opening pressure so no flow is passed on to the lube circuit. Is the 1 GPM orifice in the brake valve under the inlet fitting? Capping the line to the brakes would soon eliminate the brakes as being the problem. If the MCV was apart then all bets are off since there is now way of knowing if things were reinstalled correctly.

The more common reason for the low pressure in the TA control circuits but the steering being good would be the steering check valve leaking.

The pressure was only checked at ¼ throttle at the most and T/A lever forward. I will check this weekend with the T/A in both positions and a little more throttle to see if the pressure changes.
I will also shift the T/A and observe the pressure for change.
I changed the brake valve because the old valve had a broken shaft where it attaches to the brake pedal. I adjusted the brakes per the manual for linkage adjustments. Prior to the adjustment the brake on the right side was dragging, because when you let the clutch out the wheel would act like it was dragging for a second and the tractor did not want to roll freely.
One thing I have noticed is the left brake drum feels very warm after driving a distance. The right is cool.
I have never removed the MCV valve from the tractor. The one thing that I did to the MCV valve is I disconnected the linkage from the T/A piston and removed the piston to install a new O’ring to repair a leak. That piston stops against the snap ring.
Where is this orfice that you described in the brake valve or brake line? Could that piece be missing? I am only going with what the salvage yard told me on the brake valve. It looked a little different, but not much. It bolted right up the same.

Could I have the Power steering lines crossed? I hooked them up per the manual.

Thanks for your thoughts and time.