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Alberta | This is just an information post for those who own equipment with Twin-Disk transmissions such as the dreaded Case 4994 and this may be useful if and when the original controller dies. I've had our controller sent out to be repaired twice and unless there is some way to improve them they seem to be doomed to fail again. Good luck fixing it. It is claimed that the original is engineered for exact overlap and that is great as long as the transmission is in new condition. BUT there is NO feedback into the controller to compensate for wear and altering the shift parameters (as is found in automotive applications) . FYI, after I installed a decelerater pedal, it never shifted so smooth.
This transmission is really quite simple in its operation and shifting. The original solid state controller supplied by case had quite a few complexities involving shift timing and clutch engagement overlapping as well a low engine oil pressure disengagement and more.
This controller, which can be made to replace the original when it will no longer work, is actually fairly simple.
To understand how the controller works, you need to know how the transmission works. This “Twin Disk” tranny works similar to (but not the same) as an 18 speed truck tranny . R, 1, 2 & 3 are all in a group. So you can start out 1,2,3 then it shifts into the next range and uses those three clutches again so you get 4,5,6. Then in another part of the transmission it goes into high range and starts over again. Shifting from 3 to 4 is a double shift so is going from 9 to 10. Going from 6 to 7 is a triple shift (see chart).
Basically the controller has to engage three different clutch packs to get a gear engagement. If you use a 3 pole rotary switch you can do just that. I have found and created a list of some of the major parts needed to build one. Why? Because some people have asked for this info and I hope this helps.
I have built a few controllers so far, one for myself and some for other owners. Mine is the prototype and is very complex compared to the ones that can be made with the parts listed here. The rotary switch http://www.electro-nc.com/rotaryus/d8.pdf is heavy enough to take the 1 amp load of each solenoid it controls. Also you can search eBay "Switch, Rotary, Ceramic, Open, 4P, 17 Pos." I've used 3 of them. The enclosure should be big enough to contain all the relays and the switch with room left over. To plug into the tractor’s existing plug that goes to the transmission is also listed and available online. It is the smaller plug that goes into the original controller. The only thing that still needs to be connected to the original controller from the original plug is the output speed sensor and that is only useful for the speedometer on the dash if it still works. Otherwise you don’t even need that. The rear steering will not be affected by this controller, but if the original controller fails in that area I would suggest using a steering controller from a 4890 to run it.
The wiring diagram really isn’t that complicated once you follow the individual circuits. The worst part is understanding the relays in the diagram. Here's how they work: The second one down is labeled "hold relay" once it is initiated by pushing the button, it feeds power back into itself until the power supply is interrupted. It stays live while in operation holding pole 2 engaged. It can be interrupted (stopping the tractor) by either putting in the clutch thus interrupting the power from coming through the hold disable relay. OR when going into neural and the hold disable relay is energized. (this is so that if you turn the selector switch from forward and accidentally pass neutral, it will not engage into reverse until the initiate button is pushed again, safety feature) Note that this relay uses the 87a circuit of the relay. The bottom relay just controls the power to pole 2. If you build one, make sure you bench test it to see that it works (using a test light on the connector plug pins). Follow the circuit numbers and run the wires into the appropriate locations on the connector as listed in the chart. You will also need to get a fused power source (probably 10amp is ok) as well as a ground.
For best results use a pencil type soldering gun and fine solder. Please don’t be insulted but you may want to practice on something less expensive than the rotary switch before starting.
For an optional gear selection indicator, you can buy the 4 pole switch listed and use the extra layer for indicator lights showing which gear you are in.
The parts list shows part numbers and where to order them from. You can get some of the stuff such as relay sockets and wire at many auto parts stores. I would recommend about 20 gauge wire.
I mounted my initiate switch remotely on the side of the throttle lever. Put it wherever you want though.
The solenoid chart shows which solenoids are engaged in which gear. You have to click on the attachment below labeled 4994 chart
The rotary switch contacts go “open” between selections so you may have to get used to switching it from gear to gear without going into neutral as well as skipping a few gears.
Once in operation, you can start in 1,2, or 3 with the foot clutch. But if you try start in 4,5, or 6 it will just slam into gear when the clutch is released an inch or two. Foot clutch only works with circuit T54.
The initiate button (normally open intermittent switch) makes it so you can turn the selector from N to 1 without the tractor taking off. Push the clutch in, turn the switch to the desired gear push the initiate button. When you start to release the pedal part way, and you get partial engagement the initiate button can be released. Release the clutch pedal and you can shift as normal. To stop, push the clutch pedal in all the way and release. Be sure to install a master switch and turn it off if you leave the cab with the engine running!!
If you build one please let me know how it goes, or if you need help let me know too. Before building or using this please assume all responsibility for its operation. E-mail is [email protected]
To see the chart click on the attachment labeled "4994 Transmission Chart" it is in microsoft word format
Edited by VTG 1/30/2016 10:05
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 y 4994 transmission chart.doc (85KB - 1677 downloads)
4994.jpg (70KB - 1172 downloads)
controller 1.jpg (144KB - 1073 downloads)
controller 2.jpg (106KB - 1016 downloads)
controller 3.jpg (102KB - 1053 downloads)
4994 newer version.jpg (99KB - 1024 downloads)
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| Splendid idea and solution for these controllers. I've oftened wondered when someone will come up with a mechanical controller for MX magnum trannies, so you can at least run the thing when electronic gremlins are giving you fits. |
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Texas/New Mexico Stateline | Probably would be a good idea to post this in the Wiki over on AgTalk+. It would be easier to find later.
Wish I was smart enough to come up with stuff like this. Good job. |
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MN | Pretty cool, I've been building a shift controller for our old Steiger that we installed an allison automatic in. The shift handle Steiger used is about $600, and took up a lot of space. The pictures are of the uninstalled controller. We're mounting it on the armrest. I'm using an arduino microcontroller and a pololu motor driver to run the actuator.
The upper toggle is a lift up style that will lock in forward, neutral and reverse, the same style toggle as the header and separator control in the John Deere combines. The lower rocker switch changes gears when you're in forward. The allison automatic has only 1 reverse.
The lights on the left side of the box show the gear you've requested. If you start the tractor with the top toggle selected in forward or reverse it will flash all the lights and won't go into forward or reverse until you've put it in neutral.
The box controls a linear actuator on the transmission that does the shifting. The transmission is still the old mechanical shift automatic.
The pictures show it in neutral, and 4th.
If you wanted to you could probably make something similar to control the twin disc. Could program it to minimize the "open/neutral" spots when you're shifting, and would be able to program it to shift through the gears automatically. It'd be kind of a fun project.
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Alberta | btruck you're the man!! I just googled "arduino microcontroller" and that looks even better. What would that cost to manufacture? (ballpark figure) I mean to run a twin-disk. How many output can it handle? The twin-disk needs 8 for the clutch solenoids.
Edited by VTG 1/20/2010 00:55
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MN | Arduino has 14 digital input/output pins, and 6 analog input pins that can be used as digital. To run a solenoid you'd need some more circuitry to handle the current, and the voltage spikes when you turn on/off the solenoids and some pull up/down resistors for the switches. On my controller I'm using 4 inputs for the switches, 7 outputs for the LED's and controlling the motor controller over a serial connection.
What are the bottom clutch switch and power (t77, t78) for? Are the speed sensors the transmission output RPM?
Kind of a swag for a basic setup.
Arduino $30
I'm having a hard time finding a transistor board that's already built, could probably make one for about $20.
Locking For/Neut/Rev switch $20 (Cheapest I could find, they are ridiculously expensive)
Shift Toggle Switch body $4.06, Switch actuator $1.16. A little different than the switch I'm using now, but lots cheaper.
Enclosure either $13 or $26 depending on how big the parts end up being
Serial LED display $13. To save IO pins, I'd ditch the individual LED's to show the selected gear and Just show the gear on the display.
You'd need the same connector and wiring as your setup, about $15?
About $125 in parts. I usually double that to account for shipping/screwups/extra parts needed.
You could get way more complex than the basic setup, but this should be able to almost eliminate shifting into neutral during gear changes, could program it to delay shifting out of the current gear before shifting into the next, just a few milliseconds to account for the oil flow through the transmission. Should be able to program it to skip-shift to speed, etc.
First one may not be real "pretty".
It would take a bit of playing around to get the parameters all set right.
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Alberta | Speed sensors are transmission output speed/ground speed. but not necessary for controller operation just speed readout on dash.
Bottom clutch switch is a pressure switch that goes open when the the foot clutch is pressed in almost all the way, it closes as you release the pedal and the pressure builds up in the clutch hydraulic circuit. It also is open when there is no trans input speed (no oil pumping). I used that (T77,T78)circuit to deactivate the 'hold' relay (which keeps the T53,T54 circuits engaged).
You are talking about the "high cost" of some of the parts. They all seem reasonable considering what it will do in the end. Factory controllers are in the thousands, though not even available anymore for the 4994. I think it's going to be labour that will be the cost factor.
Do you program it with your PC? |
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MN | I was thinking that to make it skip shift you'd need a transmission RPM to compare your requested gear to how fast the tractor was moving, then it would determine whether the transmission could skip shift or not. Not sure if that's needed or not.
We have an early 9170 caseih that doesn't skip shift, I understand the later ones do. I know very little about the 4994. I've been in a Case crab steer once in my life.
I think I have about 10 hours of actually figuring out programming for the Steiger controller, and 2-3 hours of putting it together on my desk. My 3 year old daughter sat on my lap and "tested" it for 1/2 an hour by making the actuator move back and forth while I was doing something else. Making a circuit board to run the solenoids would take a couple of hours.
Arduino has software you can download for free to program the controller. It's kind of like programming in C if you're familiar with computer programming. The steiger controller was the first controller I'd programmed in a long time.
You could spend a bunch of time perfecting a controller, but getting it working wouldn't take much. Getting smooth shifts and skip shift working would take some experimenting.
I've always been paranoid about costs. Too many years of getting chewed out by the bosses because something costs too much. Now the only boss I have is my wife.
If you're interested, I probably have time to get some thing going. Shoot me an email at sbeetfarmer nospam @yahoo.com remove the nospam to email if you're interested. I'm not sure what sending stuff to Canada entails, but I could find out. |
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Alberta | The shift overlap is not all that critical, the original controller made some bad shifts. Going from 6 to 7 was quite nasty. Felt like someone hit the back of the tractor with a 5 ton rubber mallet. I installed a foot operated decelerator on the throttle cable and now it shifts better than our new JD9630.
I just had to say that in response to some of the "you'll be sorry" type of comments that follow below, 1) The faulty factory controller we had running the transmission would occasionally engage all the clutches and stalling the tractor but the transmission survived. My replacement controller never failed to work properly. 2) The transmission will unfortunately not shift like a race car (LOL). The clutch fill volumes are larger than a race car and the transmission is built differently. 3) Yes my controller does indeed "just throw full voltage on the solenoid" because that's what the original one did. No (pulse width) modulation. Newer tractors do this, these ones don't. You may want to research as to whether or not the solenoids are designed to take modulation.
The "some junk rotary switches" shown in the pictures sure are robust but supply of them are limited, I made some with lighter rotary switches and added relays to accommodate for the load.
I've added a picture and wiring diagram of a control box that I made to get a tractor mobile. Do whatever you want, make one like this, make one with a rotary switch, make one with an Arduino (check out what tall35 made), try get it fixed, buy the one that doesn't have the price of it mentioned except that it isn't cheap, it's up to you.
Edited by VTG 3/25/2023 15:36
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controller 2018 1 (full).jpg (223KB - 155 downloads)
trans controller updated more 2 (full).png (143KB - 241 downloads)
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MN | Not having shift overlap makes the programming easier.
How common are these twin disc transmissions? I've heard of a few different equipment makers using them |
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| Vince,
I know it has been a long time since you posted the info about the 4994, but I recently bought one of these tractors and literally the day I picked it up from the dealer, the tractor failed and will not shift/move with any pulling power. The dealer has had the tractor for 1 year now and can not figure it out. I bought a tranny pump from the guys over at Gran Coulee and put that on, checked every solenoid and still nothing. Would there be any possible way I could ever contact you in person to ask a few questions about what you did with your control box?
My name is Steve Dziver and I am from Winnipeg, Manitoba. I noticed your address was Alberta, so I'm hopeful we might be able to talk some day. My cell number is (204) 794-7757.
Thanks in advance if you are able to reply or call. |
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Odessa, Washington | Hi just wondering if you solved the 4994 transmission issue you were having, I have 4 of these tractors
and done alot of work on them, rebuilt trany's and built my own controllers, drop me a not at [email protected]
I can give you ideas if you need it. |
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Minnesota | Since you wrote that post, Arduino compatible boards are cheaper. You can also get a power driver board (the transistor board you mentioned) http://www.cedarlakeinstruments.com/blog/archives/219 here at a pretty reasonable price. |
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North Dakota USA | If you go with this solution to fix your 4994, you may want to take note that parts for you transmission are available from Palmer Johnson Power Systems.
If you want to fix your tractor the correct way.. Anderson Custom Solutions 701-680-7122 has original re-manufactured controls available. |
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Manitoba | NT |
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Odessa, Washington | The original are just that, old 1980's tech. and they are not going to keep working by putting old
parts together . My controllers are new technology new sensors much lower cost, much better shifting
And if you need to work on the engine I can get you parts at about 10% the cost you can get them, Case wont even have them.. Hit me up [email protected] |
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Jeffersonville, OH | I will say that I can appreciate taking the time to build something to replace older controllers, but not everything is as simple as that. It may be fine for some folks, but others don't have the right "mindset" for parts that don't work 100% the same or better than the originals. From reading your description, it doesn't sound like your "controller" has any shift modulation at all? That will shift like a race car, so if you think your 6-7 shift is rough now, this will make it pretty much brutal. I won't say shift modulation is necessary for the transmissions life and parts, but most operators will not like a controller without any modulation to help smooth the shifts a bit.
I will add though, Versatile used the Twin Disc in many tractors up until about 2010 or so. They offer a "replacement" controller, and while it is not cheap, it is an option that to me is better than rigging up some junk rotary switches and throwing full voltage to your clutches when you shift. Is it worth it for a 4994, probably not for most folks, but for a 435 Versatile that failed a controller, it could be well worth it.
Chris
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MN | That's one reason I love the internet. These guys have given 3 different methods they've used to solve their problem. And then their's the one guy who isn't involved at all saying "You can't do that!"
Salesman can be a funny crew. |
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Jeffersonville, OH | If you're talking about me, I did not say "you can't do that"
I gave some reasons why I would not want to do that, or why some of my customers would not like his option for replacement...but also, the beauty of the internet, is that people can say and do whatever the heck they feel like doing.
This site is for information, and since NOTHING was said in his post about modulation of spools in a powershift, I brought it up so that folks might have that part of the information. Make your own decisions from that.
Chris |
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MN | Ha!
Spend some time reading these guys threads. They're doing more than you think.
Versy must be as worried about their secondary market going away as deere is.
Rather than fighting right to repair, and strategically nla'ing parts, companies should consider embrace new distributed repair technology, or else a subset of their customers will do it for them.
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For Case 4994 owners, "Twin Disc" transmission controller solutions
