440D hydraulic problem

DJake · February 10, 2022, 07:16:22 AM

Hi all, my last winch problem was solved by the forum, thanks again, so I thought I would run this by you. Any suggestions would be appreciated.
It's a long story but here's the short version: I occasionally lose steering and blade control. Stop the skidder, rev it up and it all comes back. Started to get worse last fall then it developed a leak by the winch shaft seal on the charge pump. I was advised to get the pump rebuilt. Just installed the rebuilt pump and now things are even worse with the hydraulics but fortunately no leak by the winch shaft seal. Found that there is very little pressure coming from pump to the main pump. No signs of leaks, filter is ok, filter relief valve is ok. Plenty of trans fluid. Suction tube seems to be ok. Tech manual shows a surge relief valve near the filter. Just wondering if that is stuck open would it cause just about zero pressure from the charge pump? Any other ideas?

teakwood · February 10, 2022, 11:08:57 AM

Quote from: DJake on February 10, 2022, 07:16:22 AMI occasionally lose steering and blade control.

that happened to me also and it was the priority valve. the valve which gives priority to steering and brakes before blade and other not so important hyd circuits

mike_belben · February 11, 2022, 10:23:11 AM

i would say that ramon has probably got it. if you only have one pressurized fluid supply that goes to multiple, independent, open center valves in parallel configuration (meaning not chained in a power beyond series string configuration) then there has to be a dividing device upstream of the valves to split the flow proportionally.

generally this device has the inlet getting full flow, and the outlet dividing into two with one having priority. so the priority port and the overflow port, any flow above priority ports minimum. the overflow port can get zero if the pump is not supplying more than the priority minimum. how it works is a spool inside moves by spring so that it blocks overflow passage and confines all flow to the priority port. when pressure is high enough (from pump volume) it overcomes the spring resistance and shuttles the spool in its bore. this reveals the overflow path which then feeds the secondary non priority device any excess fluid the main pump is moving.

as for the charge pump, theyre just like a regular pump but smaller and regulated to a low pressure. youve gotta have an intact pump that hasnt snapped a keyway or a gear etc.. an unrestricted passage from the reservoir to the inlet, and a pressure regulator valve that is functioning right. if you have those things youll get charge pressure and if you lack them you wont.

DJake · February 12, 2022, 05:14:29 AM

Ok. Thank you both for the input. I'll take a look at the priority valve.

Bncyom33 · February 12, 2022, 05:49:02 AM

I'm chiming in here not on the piece of equipment in question as much as I am the answer you received. I am a hydraulic technician and have been for over 20 years on three different aircraft. One of which I swear the engineers of the hydraulic system ended up in the crazy house the Air Force's C5 galaxy. Mr. Belben, that is one of the best explained workings of how a hydro system splits pressure, when, why and how I have heard. I've got seasoned guys who struggle to grasp hydraulics, the theory and applications behind them. Kudos.

mike_belben · February 12, 2022, 08:30:54 AM

Thanks man. I have a vested interest.

Capitalism will fail sooner if we all cant put our heads together and keep the means of production running and producing so we can raise the next generation to carry the torch and stay off the welfare.

Helping people fix their junk is my ministry. God gave me an unusual brain so i could get attention with it and give Him the credit for all Hes done for me.

C5C Tree Farmer · February 12, 2022, 08:46:04 AM

So when you had your charge pump rebuilt what exactly did they do? Unless they machined the housing and installed oversize gears you may not have gained much. When I do JD tractor transmission repair the charge pumps are always replaced with new. There is nothing left to fix on the old ones.
If possible flow rate your charge pump first to verify if it's actually moving oil at pressure.

DJake · June 25, 2022, 05:59:13 AM

Sorry I didn't respond to this sooner C5S, somehow I didn't notice it.
So, yes, the charge pump was machined and the pressure is fine now from the charge pump. I narrowed down most of the problem to the steering valve. It was shot and not rebuildable so a new one was installed and most of the problem is resolved. I still occasionally loose steering but not nearly as often as before. I've been using an ir thermometer when it acts up and have found the pressure relief valve gets hotter than everything else so that's the next replacement.
Winch is acting up again. Out of the blue it won't hold a hitch so tried the adjustment, no luck. A while back the special nut pushed completely out of the housing so I'm thinking the springs are bad. (I had pushed it back in and it worked fine for a while). I understand the 4 11/16 measurement but can't seem to find the measurement for the special nut. It seems that depending on how far it's threaded into the eyebolt it can really affect the band adjustment. Any suggestions would be appreciated.

teakwood · June 25, 2022, 07:21:57 AM

what winch? if its a 3305 i can help, the valve is somewhat complicated and has some tricks to repair

DJake · June 26, 2022, 05:31:15 AM

I was wondering that myself, but can't seem to locate any identification numbers. I'm headed over to look it over again this morning. I'll take some pictures of it if that would help.

DJake · June 26, 2022, 05:40:14 AM

DJake · June 26, 2022, 05:43:01 AM

Here's the brake cylinder Teakwood. Not sure if it's specific to the 3305. I preset the locking nut to 4 11/16 and the eyebolt is threaded about halfway into the special nut. I'll have pics of the winch housing in a few hours.

DJake · June 26, 2022, 03:42:28 PM

BargeMonkey · June 27, 2022, 01:41:38 AM

I need to take some clearer pictures of the book because this has come up before, and been a couple years since I've touched a band but it's like riding a bicycle. I HATE a 3325 winch with a passion.

Since your that far into it, pop the cover off your clutch, DONT pull the puck out of the clutch, wipe it off, slide the disc's out and CHECK the inner bolts. If they loosen up your going to think it's your band and chase it.

That piston is there more for release, doesn't really hold the band tight, what the springs are for. I've got cut wrenches

4-11/16 is the measurement, measured from the bottom off the pins, again my picture blows.

If you over adjust it your going to bend the bolt and stretch the springs and then chase it the whole way. ALL the parts can be bought from Harold's in Maine, "Randy Nason", where I get mine. I always clean my drum up with some rough paper, hard to explain to someone without standing there. Once you get them set up you don't touch them, check the cover for leaks at the pipe 2x a yr. Bands don't last forever, springs, if the band gets worn or wet forget it, I've cleaned them, burned, baked in an oven and nothing brings them back.

DJake · June 27, 2022, 06:25:54 AM

Yep, you helped me through this a year ago and I'm in the same position now. I made the wrenches, just what's needed.
I've emailed and called you about the book but haven't heard back from you. I'll try to call later if your going to be around. Thanks!

teakwood · June 27, 2022, 07:47:43 AM

Quote from: BargeMonkey on June 27, 2022, 01:41:38 AMcheck the cover for leaks at the pipe 2x a yr. Bands don't last forever, springs, if the band gets worn or wet forget it, I've cleaned them, burned, baked in an oven and nothing brings them back.

X2 , i put new bands on after not believing and fooled around for a lot of time. open the clutch and take out all the disks, are they full of oil? check if the seal of the housing and shaft is still good, inside is the wet side and outside the dry side.

post a foto of your valve, mine always has the problem there, the small brass valves need some slight polishing every 2 years

I can't find the picture in the gallery, but the two brass valves in front of the pic, which are more elevated than the other 2, (they have two special spring washer and not just one) get a glass and a 400 or 600 sandpaper, wet the sandpaper with diesel or water and slightly slide over the paper in a 8 figure pattern, very slightly until they shine like new brass, that's all it takes

DJake · June 28, 2022, 01:30:18 PM

Hello Teakwood, I got some help yesterday and had checked the things you suggested. All seems ok. Noticed that the band was shot, as well as one spring. Looks like the lock nut on the cylinder had come loose and helped cause the wear.
All put back together now but will keep your valve info handy just in case. Off to try a few hitches. Thank you all again for the help.