Craig C

Member
I've got a 4440 PS that I'm having issues with 7th gear. Tractor has just over 5000 original hours. I've got more experience and history with a 15spd, and this thing has me scratching my head. First of all it Has good system pressure and no pressure drops in any of the gears. I even bumped the pressure a little higher to see if it would act different. It is a little soft going from neutral to gear at any rpm, which could be modulation. Once In gear everything shifts tight and snaps tight until 7th gear. I realize a lot is going on to make that shift, but if it don't take, you can throttle it down and cycle the inching pedal and it will take every time. It will also pull in 7th just fine. Temp seems to make 7th a little worse. If you skip 7th and shift from 6th directly to 8th it will take gear every time. Ive studied the elements engaged chart and was hoping it was a C2 slip in the front pack, but I'm not convinced that's what it is. I hooked it to a sled and it spun the wheels in 4th gear at 17000lbs in 4th gear so that kinda rules out the dry disc on the flywheel or does it? Anyway what do you guys think it most likely is. I'm thinking about tearing into it when I get the 955 MoCo project back into one big piece instead of looking like I'm parting it out.
 
It's not the dry disc...but possibly a shift valve hanging up a bit,,when you pump the clutch that could be pulsing that valve a bit aiding the shift...I'm just thinking out loud ...The engagement of C3 is most likely where your issue is...
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Tim, are you thinking that the C3 pack is going down or not getting oil from the shift valve. I was kinda thinking I would have had it stuck to the ground tight enough in 4th to have slipped the pack when hooked to the sled. I guess that would be considered a redneck field test. I had a similar issue with a 15 speed with the C2 a few years ago. You could stall the tractor with the brake in 12th and up, but would pull in the low gears that used C2. In an 8 speed I would think that 4th would be high enough to slip it. I don't know, probably be exploratory surgery. 7th isn't that big of a deal, but I want it right because it is supposed to be there when you click into it.
 
No, I don't think C3 is failed, because it pulls when used in the other elements,,I'm thinking the shift valve is sticky, my thoughts are based on when you pump the inching pedal it seemed to help it shift,,doing that "could" kinda let things jiggle a bit to let the valve continue to go into place..and to be sure to let you know it's a bit of a guessing game from here,,I'm just sharing my long distance thoughts...removing and cleaning the valve assembly up and going back together with clean fresh gaskets may make a difference...
 
Thanks Tim, that sounds better than having to lay hands on that clutch pack. I will look into checking out the shift valve.
 
Been doing this for over 40 years..and still doing it every day...should be getting the Nack of it...I want to share all that I have learned before my brain starts to Fuzz over ...
 
I have similar issue with my 4620. Modulation is not working, shift very bad, get better when hot. Was shifting fine before putting into a container to go to Eu. Was out of oil for 2 months.

Do you think I got sticky calves too? Or poor oil? Is it possible to get a sticky accumulator piston or broken springs?
How difficult it is to clean up the shift valves?

Someone recommends me to work it hot and and the hot oil will loose the valves again, but this is not feasible right now.
 
FYI,I had a PST (power shift transmission) on a 4440 throw me a curve a few years back that would occasional slip when shifted into 7th gear. When it slipped, of coarse you had a hesitation in shift time. When testing I learned it was more likely to do this when transmission oil was up to operating temperature. I also found that when it would slip lube pressure revealed a 5 psi pressure loss indicating a element leak at that moment. When it did not slip lube pressure did not have the lube pressure drop indicating it was not leaking at that moment??. At the time I had over 25 years experience working on 8 speed PST's and never seen an intermittent element leak that would come and go like this. Being only 7th gear having this problem I was suspecting C3. Long story short it was C3 and it was not sealing rings or piston seals leaking.
The first clutch plate that lays against C3 clutch piston is flat, different than the remaining "wavy" separator plates in C3. The reason this plate is flat is it acts as a valve to block/cover C3 piston bleed holes when contacting C3 piston. Bleed holes in piston are to add cooling oil and control engagement time during C3 shifts but, must to be blocked off by flat plate when clutch plates tighten/fully engage. Problem was the flat plate had a slight .020 "dinner plate type warp. With warm oil the bleed hole would cause element to bleed/leak too long, warped plate could not flatten itself out to seal before full clutch engagement could be accomplished, and C3 would go into a full blown slipping clutch. When oil was cold the restriction in bleed holes was greater and piston had the ability to flatten warped plate faster, blocking bleed holes and engage C3 clutch before it went into a slipping condition. The slight warp in the first C3 flat plate can and was overlooked during a previous repair and created this condition. Another factor to this problem was, tractor had HP turned up giving it more ability to power through this momentary slipping C3 clutch. If you go to your John Deere dealer and have them search old service bulletins archives, this problem is published in a SIB (service information bulletin). Hope this helps. DW
 
I never thought about that possibility,,and it seems to describe this problem..good line of thought WTW,, I will keep this in mind...
 

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