Case 850 D TCV Advice needed

[TallenStl]

Good morning all,
We recently purchased (And Received) a Case 850 D from an auction it starts and (Moved) just fine off of the trailer and around our lot. We were told the brakes needed service and that fluids and filters should be changed.
A few days later we went to move it into our shop for the service and it wouldn't move in any direction in High or Low. Nothing.
After a bunch of trouble shooting I'm starting to think that the issue is in the Transmission Control Valve....
I'm guessing that while it was sitting here people were pushing on the brake pedals and that caused the (14) Clutch Cutout Spool and or (10) Piston in the TCV to get stuck in the "pressed" position and that's causing the Dozer not to move.

So the question is:
1) is this even a possible explanation of what's going on here (FYI I have already verified fluids in the trans and checked/ cleaned filters and screen)

2) if this is a possible explanation for my issue can I just pull (15) the Rear Cover and physically push the Spool back forward to test this theory instead of removing the entire TCV from the machine?


Note: if i do find this to be the issue I will of course remove the TCV and properly rebuild as well as rebuild/replace the parts in the brake system, I just need to verify if I have a "small" problem or a big expensive one.

thanks ahead of time.

 

[Coy Lancaster]

Is the hi-lo "shifter" which are two buttons on the floor. Also the clutch cutout pistons could be stuck in the declutch position. Unlikely this would happen for both sides though, but it's possible. Check the brake actuators as well.

 

[mrdc04]

Declutch button Stuck?

 

[Coy Lancaster]

There are declutch spools in the transmission control valve. They cut power to each track when you apply brakes. The brake lines run from master cylinders to control valve then to slave cylinders.
Another thing to check is the modulator valve on the back of transmission housing.

 

[Vetech63]

The gaskets in the control valve are a weak point in my opinion. I’ve had to rebuild and replace many gaskets on those type of control valves. What is your current pressure and does it drop when put in both directions?

 

[gggraham]

Easy way to check declutch spools, remove banjo bolt from the brake lines don't lose the brass washers in front and behind the line adapter. Take a small screw driver and push in on the spool, there should be good tension and it should fully return. I've seen one stuck but kind of odd that both would be stuck. I'm with Coy I'd check modulation valve for stuck if the declutch spools return.

 

[alrman]

@TallenStl Could you post some pics of this machine?
Do you have a serial number?
Just need to be sure it is a late '80's 850D (6cyl Cummins engine) or an early '70's D850 (4cyl Case engine)- as there are also differences in the transmission that will be important for diagnosing over the internet.....
What's important, in either model, - what is the driveshaft doing during this time?
Spinning as a blur in neutral or sluggishly if at all?
Does it stop when you engage a gear? (for example - FWD + LH & RH Low )