ford 3400 (3000) 3 point hitch jerky/slow after rebuild

[bobflange]

Hi, I've used the forum for information a lot before, but just registered and this is my first time posting. Lots of great information shared here and I appreciate all the info I've gotten.

I recently did a bunch of work on the rear end hydraulics of my ford 3400 (3000 rear end as i understand it) and, while many problems were fixed, the three point hitch is acting erratically (more detail below) and with winter fast approaching I'm worried it is going to fail on me in a foot of snow if I ignore the problem now. Looking to get advice on what might be causing this problem, and how I can fix it (or if I shouldn't worry).

Background:
- I've owned the tractor for the last three years and the 3ph has always worked fine with the exception of not holding position control (already solved)

- I recently had to split the tractor at the rear housing/transmission junction and while I was in there did a full lift cover overhaul as per the service manual. This included new o-rings/gaskets on all parts of the lift cover, hydraulic intake/return manifold, new return filter, cleaned the suction filter, adjusted all linkage in accordance with the manual. Also did the overhaul on the flow control system.

- When I got the tractor back together everything worked, but the 3ph was very slow. Ran it for a few days and realized I still had the flow control valve turned completely all the way out from one of the checks I had to make during reassembly. Turned the flow control back in and it seemed to work better but as I was testing it, it started acting really erratic: a couple times it wouldn't lift for 10 seconds, then would lift some very slowly and pause, lift etc. Sometimes it would lift steadily, but would take a full 10 seconds to get from ground to full height.

Things I have already checked:
- removed allen plug on pump to make sure it is primed, shot a ton of fluid out so I'm guessing it is good.
- Hydraulic fluid is full (double checked after priming)
- Fluid is correct spec (universal hyd/trans tractor supply)
- No visible damage to suction/return lines outside housing, but haven't had them off tractor

Other possibly relevant info:
- very small seeping leak from accessory cover on top of lift cover (where you attach a remote)
- no visible leaks anywhere else
- a minor but persistent rear end leak (what I split the tractor to fix) over the last year may have caused the pump to have run without fluid for very brief periods (2-3 minutes before I realized I couldn't lift the 3ph on two occasions) on only one occasion did the pump have to be re-primed due to the fluid level dropping too low. Could pump be dying?
- 3ph is currently lifting and holding a ~1000lb rear blade (weight has been added to it)
- fastest it will lift this blade is about 8 seconds, and it's taken up to 20.

Apologies for the long post, wanted to provide all the info I could, thanks for reading if you got this far.

 

[Soundguy]

did you have the intake pipe off the pump where the comp nut is?

 

[bobflange]

Hi Soundguy, I remember reading a lot of good advice from you over the last few months in the threads I saw here and elsewhere, glad you saw the thread.

I did not take the intake pipe off the pump. Aside from the set screw I removed and replaced to make sure the pump was primed, I didn't do any work on the pump. I did have the manifold where the suction and return hoses connect to the rear center housing off but that's the closest to the pump I got.

 

[Soundguy]

did you repalce all orings there?

 

[bobflange]

I did replace all the o-rings on the rear axle hydraulic line manifold. The large one I ordered by part #, of the two smaller ones - I found a spare in the lift cover o-ring kit that fit one, and put one from a standard o-ring set in another. O-rings protruded slightly, plate was clean on both sides etc. and tightened evenly. Plate is not leaking fluid, so is it safe to assume it is also not sucking air?

Leads me to a thought though: any way to test if the system is sucking air? A couple of the people I have asked about this problem bring up air getting in the system as a possible cause, but I'm not sure how I could verify or troubleshoot that.

I've probably cycled the 3ph 50 times since the rebuild but is there any chance that something just needs to get more use to work properly?

 

[Soundguy]

does that 3400 have a 3x5 option cover on top of thecenter section with a plug in it/

if so het a pipe to nipple adapterand a piece of clear hose and aim that back over into the hyds fill and run it.. look for foam or bubbles

 

[bobflange]

Soundguy, thanks for sticking with the thread, hoping to figure this out before we get hit with snow. Yes, I do have the accessory cover. There are two hex nut machine bolts that go in the accessory cover (other than the 4 perimeter ones that appear to just be the mechanical connection). Would the one you are referring to be part # 371433S36 which is #14 on the lift cover diagram in the parts manual? This is the larger of the two bolts in the center of the accessory cover and has a washer. If that's the one you mean I'll have to buy a 9/16"-18 pipe to nipple and some hose but I should be going by a hardware store tomorrow. Will the fluid that passes through this hose be under high pressure? Want to make sure I'm not risking a hand if I just buy regular clear hose.

Am I correct to assume this should tell us if air is getting into the lines/passageways before fluid gets to the lift cylinder?

I worked the system about 40 or 50 times this afternoon to see if things would get any better. Ran things a while to get everything up to temperature and cycled it repeatedly. Was about a 20-25 second lift in the beginning, with occasional non-responsiveness for up to a half minute after lifting quadrant handle. By the end of the 30-40 times (figure half hour later, as I was working on other things too) it was lifting in 8-12 seconds 9 out of 10 times. The other 1 of 10 it still paused or took longer.

 

[Soundguy]

there should be a smaller one like 5/16 and then the larger one for the oil.

remember.. pressure is a function of flow under restriction.

the only restriction that oil will have is drag from the hose sides.. if restricted.. it could pressurize to 2250-2500 at full open relief. at full tilt you don't even make 8gpm.

that's like full out 3/4 gargen hose fow.

flow.. no real pressure..... don't hold your thumb over it...

 

[bobflange]

Thanks for the explanation, makes sense. Tried to find a 9/16-18 nipple adapter at a couple places today and didn't have any luck, not a common size so I'm thinking I need to find another way to test this other than having the correct thread adapter. Any ideas? Is there an alternate place or method to test this same thing. I didn't have any luck finding 9/16-18" fittings (or even adapters) online either.

On the plus side, picked up a set of pie weights for the tractor today, looking forward to the improved traction.

 

[PBettis]

Sounds like issue in the flow control assembly. Could be the linkage in sump area connected to flow control adjustment. Just resolved several issues inside a 3000. Found very restricted filter/screen (2) and gear retainer ring flopping between pto engagement gears. Repaired by having gear drilled and tapped for (2) set screws with red loctite. Assumed the pto could engage itself and didn't want that of course. But sounds like either trash made it into hyd supply line when you removed screen assembly to clean possibly going to the pump itself or a flow control issue posibly linkage...?? The cap on end of hyd.screen popped off on ours so we had to repair with (2) bolts and nylock nuts with cotter pins to insure hyd fluid screening. Hope this helps.