JD400 Reverser - No Forward

All linkage and mechanical is good - I have replaced all the clutch pedal shaft parts and adjusted the shaft to clutch control valve so that the hydraulic tap pressure is max (150 psi) when pedal is released at stop.

I probably should have stated that when I began the restoration process, this tractor had been sitting out in a field for about six (6) years. Just before teardown, I ran it and exercised all hydraulics in an effort to identify everything that was broken - everything worked albeit the tractor looked terrible, felt loose and worn, and only ran on 3 cylinders (broken rod but still ran).

Tractor now has a freshly rebuilt 4219 diesel with a rebuilt injection pump, new flywheel clutch, and a clean fresh paint job (at least from the transmission forward). Maybe I'm OCD but I have disassembled every single nut & bolt & part and cleaned/painted or repaired/replaced as necessary. From the transmission forward, it looks and runs like a brand new tractor.

After a great deal of cleaning and flushing, all the hydraulics work great; everything except that the tractor will not move forward (but it will move in reverse just fine). Transmission pump pressure seems to be fine, pressure tap at the rear of the reverser control valve reads 150 psi. The 'reverse' pressure tap on the top of the RCV reads 150 psi when clutch is released (goes to 0 when clutch depressed). The 'forward' pressure tap on the top of the RCV does not show any appreciable pressure at all.

I am guessing that there is either a stuck valve or channel or something inside the RCV that prevents flow of oil to the forward disc pack, or maybe something blown or open in the oil line to the fwd disc pack or the fwd clutch drum itself. When I had the tractor broken in half to replace the engine, I removed/disassembled the forward clutch/disc drum for inspection and it looked very good (even replaced the oil bushings inside of it just for good measure). At least what I could see inside the transmission case from there looked good.

Next step I guess I will remove and clean/inspect the reverser control valve and look for 'something wromg'.

This has been a fun project - when I am completely done, I will have a clean, like-new 40+ year old tractor. I'm even thinking about the 1968 Plymouth Barracude that I am also restoring and painting it John Deere green.

Thanks for your confirmation - makes me feel better about hoping the problem is in the reverser control valve, something more easily fixed. I wasn't looking forward to breaking the tractor in half again.

Only question I have at the moment (I'll find out soon enough I guess) is will I have to drain all the hydraulic oil from the transmission when I pull this valve assy off? Or is this cavity in the transmission case isolated so that won't happen?

Actually, I do have another question: Is there any 'interaction' between the brakes and the reverser control valve? I can't find anything in the manuals that suggest this, but I only considered it since the brake control valve assy mounts onto the outside of the reverser control valve and I began to wonder what happens (hydraulically speaking) when brake pedal is depressed if clutch pedal is not.???

Thanks for your input.

Thanks, jd110, for your help and advice.
(yes, the tractor did operate in forward & reverse before the teardown - and did so with a gaping hole in the side of the engine block where the #4 rod went through it and the #3 piston was severely cracked)[Nothing runs like a Deere!!!]

Here's what I have found so far. I removed the reverser control valve assy from the tractor, exercising care to not break loose the valve plate from the side of the clutch housing so the oil tubes don't fall out. I only dropped about 4 gallons of fluid.

I disassembled the valve assy, noting that it was full of sludge, but otherwise everything appeared to not be excessively worn or scored; except there was one valve that was stuck - see attached diagram (hoping I uploaded correctly): the pin, item 18 (the one associated with spring item 19) was stuck in - had to pry out with screwdriver (did not damage it). I have not yet figured out if this fault would cause problem for sure (but I'm hopful).

I also tried a little experiment to make a guess on the integrity of the oil tubes and fwd clutch pack inside the clutch housing (I have considered possibility of sealing rings or tubes or anything else in fwd clutch being damaged). I took a rubber hose and alternately blew some pressure into each the fwd & rev oil tubes at the side of the case. I know this is air vs. oil and they will not be airtight, but I would expect some resistance - and since reverse side is believed to be good, I figured I could relatively compare the amount of resistance/backpressure on the reverse side to that of the fwd side, expecting them to be 'about' the same. I could feel considerable resistance blowing into the reverse side, I could feel some resistance blowing into the forward side but not as much. Bummer! But perhaps this may be partially explained by the fact that the reverse parts should be well soaked/lubricated which would make then seal better, while the forward parts are probably near dry since no/little oil has been pumping there, making them seal not so well.(?)

Right now I am inclined to reassemble/reinstall the RCV Assy and try it out. If it still doesn't work, then I guess its back to the jacks to split the tractor in half again to check out the inside of the clutch housing.

So, what do you think?

I thought I'd check in to post update, in case anyone is interested and to solicit further comment/advice on how I'm doing.

I have completely rebuilt the Reverser Control Valve (called RCV henceforth), and reinstalled it - clean as a whistle, all valves/spools move freely, all lands smooth, etc - I still have the same problem: everything works fine, except the tractor will not move forward. Now I'm looking to the clutch/reverser housing, but want to make absolutely sure before I break the tractor in half again, so I checked a bunch of things (all measurements with tractor warm @ about 2,000 RPM):

1. Rechecked all pressures: 155psi at RCV accummulator; 0-155psi at reverse tap (clutch depressed to engaged); 0-0psi at forward tap (not 10, not 5, not 2, but 000).

2. Connected tubing to each port to verify flow: get really good strong flow from reverse tap as clutch is engaged; get just a trickle from forward tap as clutch is engaged.

OK, I understand this is still not conclusive - if fluid is being dumped back to sump inside the housing, fluid will still follow path of least resistance, not building pressure/flow at the tap.

I am inclined to try one more experiment before I give up and put tractor back on jacks, and am curious what anyone might think about this: I have fashioned a plate from 1/8" thick aluminum and have cut all holes in it so it looks exactly like the gasket between RCV and housing, except that the holes that go to the rev & fwd oil lines are just tiny pinholes (guaranteed to create back pressure and identical to do comparative testing) [should be OK since lube lines are separate, will still limit to short durations for safety]. I will again be looking for same pressure at fwd & rev taps. If pressures are significantly different, then has to be problem in RCV (although wouldn't preclude multiple problems). If pressures are about the same, then RCV has to be OK and problem is definitely in housing.

Only other thing I've considered, remembering from when I rebuilt automatic transmissions: In some freshly reman auto trans, there can be e pressure spike at first run that can crack the aluminum pistons in the clutch packs (happenned to me once, had to tear down again and replace w/ steel piston). I think the pistons in the reverse brake and fwd clutch pack are aluminum. Is anything like this ever known to happen in tractor hydraulic clutches?

Any thoughts or suggestions???

Thanks for reply, and I appreciate your response.

Your suggestion that there must "be a sizeable leak to have zero pressure" is my top interest and biggest concern at the moment; almost makes me think that something must have come completely loose to be that bad. The thing that puzzles me the most, is that it worked (it moved fwd and rev) before I replaced the engine - if problem is in housing, maybe I damaged something putting back together, or is it possible that 5 years of freezing/thawing with much moisture inside may have broken something loose.?.

and I am about 99.4% sure that the problem is not in the valve since pressure and flow are both good in reverse - only thing different between fwd and rev is the tail end of the oil path as is being directed into either the fwd or rev oil tubes to respective disk packs. I would think that if any problem in the valve could cause that, it would have been obvious during inspection when I had it out.

My idea behind trying the experiment with the plate may be more of an attempt to prove the obvious, but I guess I was hoping it would either:
1) get me from 99.4% to 100% sure of problem source in housing, or
2) reveal by some miracle that problem is in valve & easily fixed.
Here's how it would work: the plate, in essence, would be nothing more than a spacer (like a 1/8" thick gasket), allowing normal operation - with exception of not having holes in it where the fwd & rev oil lines are (or actually pinholes that would simulate normal leakage in/around disk packs). The goal/purpose is to "eliminate" what seems to be an apparenly huge leak in the fwd circuit by blocking/plugging the fwd oil line (may be another way, but this seemed easy to implement and undo - imagine putting a plug or something inside the fwd tube to "eliminate" the leak and oil pressure pushed the plug way up inside the tubing...). Obviously, the tractor could not move, but I could repeat all the pressure/flow checks and prove with 100% certainty where problem is. The expectation would be to see good pressure/flow at both fwd & rev pressure taps on top of valve since now both would be presented with equal and adequate restriction - making 100% conclusive of housing problem. Yet, there'd still be a small glimmer of hope that test results might be same as they are now, which will prove a valve problem (something overlooked during disassembly/inspection), and easily fixed.

Work is going slow during these winter months; the tractor is outside and I keep it well covered - I avoid all the effort to uncover/recover unless I know it'll be dry/warm for several days in a row.

I may have a new development or just a new revelation. I took tthe reverser control valve back off, and I paid closer attention to the two oil tubes in the side of the housing going to the rev & fwd clutches. The tube going to the fwd clutch was sticking out a little, maybe 1/8", while the tube to the reverse brake was recessed in the plate by about 1/8". At first, I thought this might be normal, like it functioned as an 'alignment pin' or something (the tube from the transmission pump also sticks out just a little). But now I'm questioning it - I played with it a little, it seemed a little loose, so I took the plunge and removed the side plate, making sure that none of the tubes came out with it. All the rest of the tubes seem fairly snug, except the tube going to the fwd clutch. It is really loose and sloppy. I can't see the other end of it, but I'm guessing that it has either come out of it's hole on the other end, or maybe has a crack or break in it. I have not yet tried to pull it out - I thought I would educate myself a bit more before trying that.

What can I do now? Is there any way that I can inspect the other end of that tube? (mirrors, laproscope, endoscope, ?) Is there anyway to reinsert that tube back to its home without tearing down the tractor? And if I tear down the tractor, does only the engine need to come off (access from front of clutch housing in the fwd clutch cavity), or engine & clutch housing together (access from back/inside of clutch housing)?

Given your (jd110) comments and what I have experienced, I am pretty much convinced there is a problem with that line. I do not have a borescope (but it would sure be nice), I have tried to put a small mirror up in there to see (that fwd oil tube goes around a blind corner) but there are so many tubes that I can't see anything. I have tried to pull that tube out, but can't; its seems to be still attached/inserted to wherever it goes, so I can't tell exactly what has happenned to bring about the looseness. There is a bar behind the bend in the tube to keep it in place when installing the side plate, which also seems to keep me from removing the tube through that side opening.

Looks like I must split the tractor to go any further. There has to be a problem with that tube.

I guess I'm down to one final question, do I need to split the engine from the clutch/reverser housing first, then remove the clutch/reverser from the transmission? Or can I just split the tractor between clutch/reverser housing and transmission? The procedure in the manual calls for the double split, but it seems to me that as long as I have adequate support for the engine/reverser assy, I should be able to split it between clutch/reverser and transmission housings. (However, I understand that if I want to inspect the fwd disk pack, the engine must be separated from the clutch housing.)

Update:
I have split the tractor between reverser and transmission housings, and I have "gutted" the reverser housing to gain access for inspection inside. The hole where the fwd oil line goes looks fine except that the o-ring inside it looks pretty raggedy and flattenned (see photo). The tube itself looked fine. But what got my attention was how loose the fwd oil line was and how easily it fell out once I got inside. I still have some checking to do, but it seems as if the tube was either not pressed inside the hole all the way or the tube was a bit too small for the hole or both. I have even been a bit suspicious that the tube may have been a bit too short and consequently may have moved around so much over 35+ years of use that the circumference of the tip of the tube may have been compressed just enough that it did not seal in the hole.

1. I need to do a "compression" test at the hole to see if there may be additional leakage further inside or in the fwd clutch drum (subjective, looking for back-pressure at least as tight as the rev clutch pack was and better than fwd line test was before).

2. I need to repeat "compression" test with tube inserted (and new o-ring replaced) to see if any additional leakage is occuring at the hole seal (again subjective, looking for back-pressure at least as tight as before). Should do this with side plate attached so tube is in proper position.

Depending on how these tests work out, I am considering lengthening the fwd oil tube a bit by splicing it with a compression/bite hydraulic union, making it long enough that I can cut the end of the tube off that has become compressed. I could just buy a new tube for about $35; the fitting would cost about $9.

Of course, if I determine that there is more problem inside the fwd clutch pack, then that changes everything.

And I have considered that as long as I have this much torn down, I may as well go ahead and completely overhaul the reverser housing (which includes all the steering system). We'll see...

I'll keep you posted.
Thanks.

Now, its a done deal. The tractor is back on-line, running great.

I completely overhauled the reverser unit, except for replacing the actual disks/plates (they looked to be in great shape); replaced all seals, bushings, o-rings, etc, and polished ends of all oil tubes. The inside end of the fwd oil tube had become just a little bit out of shape, so I tweaked it a bit to get it perfectly round and polished for a good seal on the o-ring. It still seemed a bit floppy, but I did pressure tests and it seemed to hole well (must have been that way from the factory). Got it all put back together, adjusted clutch and pressures, it runs very good.

And oh by the way, I did experiment with the fwd oil tube a bit; everybody kept telling me that if it falls out, there is no way to get it back in without spliting the tractor - I found that it is possible to get that tube reinserted back into its hole from outside the housing, but it is very hard and time consuming. Now, the tube won't come out thru the opening in the side of the housing - there is a bracket behind it to keep it in place when repositioning the side plate. So if the tube must be replaced, the tractor must be split. But if it merely fell out when servicing the reverser control valve, it can be put back in. The real difficulty is that you can't see up in there and there is very little room to maneuver. But since the hole that the tube inserts into faces toward the rear of the tractor, I found it possible to to keep blindly poking the tube forward until it just happens to go right into the hole. You only need to find a way to get a firm grip on the outer end of the tube (I did with a wooden dowel stuck inside it and vise-grips with a rubber sheet to cushion it on the outside) and to possess a lot of patience - it may take a long time and many bruised knuckles to happen upon the right poke that lands in the hole, and then enough force applied forward to get it inserted all the way to seal with the o-ring. (even though I didn't need to do this, I just wanted to prove whether it could be done)

THANKS FOR ALL HELP AND ADVICE......