8 speed Powershift is this true?

[SmalltimeJd]

I don't know all that much about the PS. My problem is C3 pressure is low. System pressure is good. Lube pressure is good. I was told, if lube pressure is good while the C3 element is engaged, there is no leaks in the C3 pack. So that rules out shaft seals, clutch drum piston seals, C3 oil line, fittings and bearing quill.
Is that true? [/b]

 

[Hay maker2]

C3 is worn out.
Needs new drive and driven plates. Might as well do C1, C2, the PTO pack.
I had the same issues on my 4020

 

[SmalltimeJd]

(quoted from post at 10:02:46 02/10/22) C3 is worn out.
Needs new drive and driven plates. Might as well do C1, C2, the PTO pack.
I had the same issues on my 4020

You're full of good news.
I did C1 C2 and pto couple years ago, so at least they're good.

Where does the lube pressure come from? I was told it's the left over oil from the what ever element is engaged. C1 C2 ect. So if you have a leak in C3, you would have very low or no lube pressure. I'm guessing that's not true?

This post was edited by SmalltimeJd on 02/10/2022 at 09:41 am.

 

[Hay maker2]

C3 is worn out.
Needs new drive and driven plates. Might as well do C1, C2, the PTO pack.
I had the same issues on my 4020

 

[Hay maker2]

If you had low live pressure you would have low pressure on all the clutches and brakes.
My 4020 had the save issues on C1andC2.
The issue was the plates were worn thin and there was not enough travel in the piston to clamp the plates and create the required pressure to lock them together

 

[WTW]

You are correct in your thinking. There is only one transmission pump that supplies all the transmission system pressure including lube circuit. Transmission pressure regulating valve
works like a priority valve controlling system pressure to all transmission clutches and brake elements. When they are satisfied / meet pressure requirements, the excess oil from
transmission pump open pressure control valve and spills over / supplies lube circuit. When lube pressure meets it limit, there is a lube relief valve that can open and dump to sump which
doesn't happen often usually with very cold oil. So if there was a leak in C3 there should also be a drop in lube pressure when C3 is engaged. The only reason lube may not of dropped is
that you were checking pressures at too high of engine RPM which will produce more transmission pump flow and miss lead test. Set engine RPM to only have low lube pressure 5-10 psi. then
shift through transmission speed to see if lube pressure is lost at any given gear. It is normal to see lube pressure dip and then it should come back to same or near same lube pressure
once the selected element has filled. If lube pressure is good / same in every gear and C3 pressure is low I would question a shift valve possibly hanging up?? DW

 

[SmalltimeJd]

(quoted from post at 14:51:32 02/10/22) You are correct in your thinking. There is only one transmission pump that supplies all the transmission system pressure including lube circuit. Transmission pressure regulating valve
works like a priority valve controlling system pressure to all transmission clutches and brake elements. When they are satisfied / meet pressure requirements, the excess oil from
transmission pump open pressure control valve and spills over / supplies lube circuit. When lube pressure meets it limit, there is a lube relief valve that can open and dump to sump which
doesn't happen often usually with very cold oil. So if there was a leak in C3 there should also be a drop in lube pressure when C3 is engaged. The only reason lube may not of dropped is
that you were checking pressures at too high of engine RPM which will produce more transmission pump flow and miss lead test. Set engine RPM to only have low lube pressure 5-10 psi. then
shift through transmission speed to see if lube pressure is lost at any given gear. It is normal to see lube pressure dip and then it should come back to same or near same lube pressure
once the selected element has filled. If lube pressure is good / same in every gear and C3 pressure is low I would question a shift valve possibly hanging up?? DW

Thank you for your response. I understand the system a little more clear now.
When I check lubed pressure, I set the rpms so I had 10psi. Which was right around 1100 rpms. I shifted through every gear. Like you said, the pressure went down then came back up to within 2-3psi of the original 10psi.
I too, thought of the C3 shift valve hanging up. I have the housing off the tractor now and the shift valve moves freely in its bore without any binding. This is really turning into a mystery.

 

[WTW]

Good work. Even with C3 wore out, and if it did not effect the piston seal (which it should not) pressure in C3 test port should not be effected?? Take a look if C3 pressure port is
before or after the shift valve to see if we are seeing true element pressure. There is a couple element ports that can miss lead on some versions of 8 speed shift valves?? It is not
uncommon to see a bit more lube pressure loss when C3 is engaged because there is more rotating sealing rings used to get pressure oil to revolving c3 clutch located in the back of
planetary pack. DW

 

[SmalltimeJd]

(quoted from post at 15:20:22 02/10/22) Good work. Even with C3 wore out, and if it did not effect the piston seal (which it should not) pressure in C3 test port should not be effected?? Take a look if C3 pressure port is
before or after the shift valve to see if we are seeing true element pressure. There is a couple element ports that can miss lead on some versions of 8 speed shift valves?? It is not
uncommon to see a bit more lube pressure loss when C3 is engaged because there is more rotating sealing rings used to get pressure oil to revolving c3 clutch located in the back of
planetary pack. DW

I never thought of that, you're right. There is an early and later housing. I have the early housing, the test port is before the shift valve.
The test port is just an inch away from the left accumulator.
So that means be have low pressure before the shift valve?

Could there be something wrong with the accumulator? Not letting oil to the shift valve? But it seems odd, that accumulator allows oil to c3 b3 and b4. Wouldn't I also have problems with b3 and b4 if for some reason the accumulator was sticking?
And yes, you're right again, all other elements I had 1- 2psi lube loss, c3 I had 3psi

 

[WTW]

Thinking some more on your symptoms and test pressures here is what I think you have going on. All clutch elements including C3 have the first clutch steel plate that is flat. Then a
disk and then a wavy plates between remaining disk. The reason the first plate is flat is that it lays flat on clutch piston face to cover piston bleed holes in piston face when fully
engaged. (Plate act like a valve) Bleed holes in piston are factory man made / controlled leaks in clutch element piston to control fill times. If in event the first steel / plate plate
becomes warped from slippage it can allow the clutch element to constantly leak when it should not and result in a lower engagement pressure in that element. The bleed holes size is not
big enough to effect lube pressure enough to be obvious but enough to drop clutch pressure. This plate can cause this condition with warp in the .020 or more range. Seen this years ago and
at the time had me scratching my head but this is what I found and if you could get into old JD SIB's (Service Information Bulletins) there is a service bulletin written about this
condition. DW

 

[SmalltimeJd]

(quoted from post at 16:40:54 02/10/22) Thinking some more on your symptoms and test pressures here is what I think you have going on. All clutch elements including C3 have the first clutch steel plate that is flat. Then a
disk and then a wavy plates between remaining disk. The reason the first plate is flat is that it lays flat on clutch piston face to cover piston bleed holes in piston face when fully
engaged. (Plate act like a valve) Bleed holes in piston are factory man made / controlled leaks in clutch element piston to control fill times. If in event the first steel / plate plate
becomes warped from slippage it can allow the clutch element to constantly leak when it should not and result in a lower engagement pressure in that element. The bleed holes size is not
big enough to effect lube pressure enough to be obvious but enough to drop clutch pressure. This plate can cause this condition with warp in the .020 or more range. Seen this years ago and
at the time had me scratching my head but this is what I found and if you could get into old JD SIB's (Service Information Bulletins) there is a service bulletin written about this
condition. DW

This definitely makes sense. It's not something I wanted to hear, I was really hoping I wouldn't have to split, remove cab, ect.
I will search for old SIB's and see what I can find.
Thank you for all your time and help, it is greatly appreciated.


I found an old thread that you posted in 2017 about this exact problem. You said it happened on a 4440. What are the chances, this is also a 4440.
I see in your old post you said 7th slipped. My 7th does not slip. On the road you hit 7th, you can hear the torsion damper squeal for a split second and you're gone. But I do believe I'm having the problem you described.
Thanks again.

This post was edited by SmalltimeJd on 02/10/2022 at 04:40 pm.

 

[WTW]

I found an old thread that you posted in 2017 about this exact problem. You said it happened on a 4440.
What are the chances, this is also a 4440.
I see in your old post you said 7th slipped. My 7th does not slip. On the road you hit 7th, you can hear
the torsion damper squeal for a split second and you're gone. But I do believe I'm having the problem you
described.
I been involved in many 4440 PS transmission repairs. I set up many new 4440's in the late 70's and early
80's. I always said the 4440 was more tractor than it had transmission when it was a PS because they were
prone to slip under load and during shifting. You saying it does not slip in 7th kind of rules out C3
because 7th gear is direct drive and uses all 3 clutches in transmission to drive tractor, C1, C2 and C3.
In the early days of the 4440 I had new ones and many sense then that would slip under load when roading
grain wagons, I worked with the company at the time (1982) through the dealership I worked at and fitted
new tractors with the improved clutch disk & plates that are now current service part clutch disk and
plates. Service disk and plates different than the original and are not wavy plates rather ground flat
plates. Disk are not the original diamond pattern rather grooved pattern. The later design disk & plates
was changed to increase clutch capacity and stop slippage. If you have a 4440 with good torque or set up
on its HP It is very common C1 and C2 will slip if equipped with original clutch plates and disk. If you
have an old tractor and the torsional dampener slips this too will cause transmission to slip / fail
because when it does slip, transmission pump slows down dropping system pressure, transmission slips, When
transmission slips then torsional damper comes back in driving pump again and slips transmission clutch
back in which just raises havoc with the transmission clutches when tractor is under load.

 

[SmalltimeJd]

I been involved in many 4440 PS transmission repairs. I set up many new 4440's in the late 70's and early
80's. I always said the 4440 was more tractor than it had transmission when it was a PS because they were
prone to slip under load and during shifting. You saying it does not slip in 7th kind of rules out C3
because 7th gear is direct drive and uses all 3 clutches in transmission to drive tractor, C1, C2 and C3.
In the early days of the 4440 I had new ones and many sense then that would slip under load when roading
grain wagons, I worked with the company at the time (1982) through the dealership I worked at and fitted
new tractors with the improved clutch disk & plates that are now current service part clutch disk and
plates. Service disk and plates different than the original and are not wavy plates rather ground flat
plates. Disk are not the original diamond pattern rather grooved pattern. The later design disk & plates
was changed to increase clutch capacity and stop slippage. If you have a 4440 with good torque or set up
on its HP It is very common C1 and C2 will slip if equipped with original clutch plates and disk. If you
have an old tractor and the torsional dampener slips this too will cause transmission to slip / fail
because when it does slip, transmission pump slows down dropping system pressure, transmission slips, When
transmission slips then torsional damper comes back in driving pump again and slips transmission clutch
back in which just raises havoc with the transmission clutches when tractor is under load.[/quote]


It's safe to say you're not just an average person on this forum, your resume is very impressive!
I know of the wavy plates you speak of, c1&2 were slipping, you could see the high spots on the plates where the disk was contacting. I put a new torsion damper in at that time as well. I put one washer under each spring, as suggested on this forum.
And a new trans oil pump.

That's what I find odd, shouldn't 7th slip just as easy if not easier than 1-4th gears?
Jd should have the gaskets needed to get this housing back on today. Once I get it together I will try to slip 7th again. And I will see if it's easier to slip 1-4 once the oil gets warm or if it slips the same cold or warm.