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Late 8 Speed PS dampening valve

F

fdt860

Well-known Member
On the late graders 570B, 670B, 770B that were still using the 8 speeds PS, Deere added this valve at the end of the accumulators.
What is the benefits of this? Would a 4620 benefits from having this? I have the opportunity to buy this plate from a 570B at a salvage yard, and I wander if this would benefits a 4620 that is a fairly rude ride.

RXP021457______UN20FEB96.gif


Deere also added a C1-C2 modulator assembly, on the 670B and 770B to 772BH, behind the clutch valve. This would requires to redo the routing of the main hydraulic lines from the hydraulic filte, but again, what is the benefit of this appendix?

0000404760____________A1.gif


To be noted that 772BH is last application of the 8 speeds PS and Deere HFWD, in about 1994!
 
That is an interesting idea,,I have thought about adding an accumulator to a test port to cushion the shift in a couple speeds.
 
Both of these make the shift smoother on the grader. I think that they would do the same on your JD 4620 PS.
 
Thanks for the inputs. In all my wandering on the 7020 PS project idea, I saw that Deere installed an accumulator on the shift valve.
That accumulator is used on all the graders, that can go from F7 to R7 in theory... It looks similar to what they had on the 55 series tractor, but I may be total wrong.

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Tims, can you explain what an accumulator with 2 lines feeding each side would do?
 
I also figured out that the 4620 does not have the accumulator in the clutch housing that the 4520 has. It seems to me that the tractors with the accumulator in the control valve does not shift as smooth as earlier design with accumulator in clutch housing.
So I should install an extra accumulator in the clutch housing, the 4620 wllow for it anyway. It is just blocked.
 
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