Powerquad Forward Cluch Problem

[JohnS1970]

Have a 2002 6420 with a Powerquad 24 speed that lost forward clutch pressure baling 2nd cut late last summer. Should have 205 psi had 80 psi. Reverse had 205
worked fine all 1-2-3-4 shifts worked fine. Pulled transmission this winter rebuilt forward clutch, all new seals, all new gaskets, oil pump gears and clutch
housing that it mates to were scored up more than I liked replaced housing and pump gears put it in same thing 80 psi. Checked the shift valves above the shift
solenoids don't see a problem there. Before I pull it back out is there something I'm missing? I'm sure it's possible I overlooked something in forward clutch
when I had is apart but I find it strange I have the same problem before and after. I pulled the B!,B2,B3 brakes and C4 clutch apart and they looked good. I
wasn't happy with the reverse brake clutches and replaced them. Before reverse was a bit soft on engagement compared to forward now it is nice and firm without
being harsh just the way you would want it. The only housing I really didn't go through was the front valve body. I'm thinking my next step is pull the valve body
and inspect for possible issue there or is there something I overlooked when I had it apart? And I have and used the factory manuals and pressure gauges.

 

[rockcreek4630]

What does lube pressure do. If lube is good did you check modulation valves.

 

[JohnS1970]

Lube pressure checks out when you shift to reverse drops and then gradually recovers as it routes cooling oil to brake. In forward there is a bigger pressure drop and it takes longer to recover. What do you mean by modulation valves?

 

[rockcreek4630]

Do you have mechanical or electrical reverser there's modulation valves for engaging so when you shift it doesn't slam in.

 

[JohnS1970]

Electric reverser the shift solenoids and shift valves have been interchanged forward to reverse problem remains on the forward side. My understanding is the enable proportion solenoid pulses the apply oil to gradually apply oil pressure to shift valve. If it was the issue shouldn't I have trouble with reverse also?

 

[rockcreek4630]

Are you hooked up to forward clutch testport or system test port.if lube and system pressure recover you don't have a leak. I don't have any books working of of 6 year old memory. You said you have books go through the valves they name them there's an accumulator piston and they would have seals go bad and the clutch cooling valves went bad and caused problems.

 

[JohnS1970]

80 psi on forward clutch test port 205 psi on reverse brake port. Didn't check system pressure as reverse brake pressure was at 205 so I assumed system pressure was good. Lube pressure recovered on both forward and reverse shift as per manual however on the forward shift the pressure drop was greater and took longer to recover. I pulled the clutch cooling valve and clutch control valves and didn't physically see any trouble. When I installed a new clutch housing I changed all the valves from the old housing to the new one and didn't see anything unusual. The valve body was cleaned and a new front seal installed no valves were removed. The shift valves and forward/reverse solenoids have been swapped side to side with no change. The cooler relief valve and lube relief valve haven't been touched but I can't see them causing a problem. I'm thinking my next step is pulling the valve body and inspecting as it is really the only thing I didn't have apart.

 

[rockcreek4630]

Check system pressure if it is good in in forward you have a valve problem and your next step is Wright. When you're hooked to forward test port you are reading after valving so you don't know if it is valves or a leak.

 

[JohnS1970]

Gotcha now I see what you're getting at. Am I correct in thinking a problem with the cooler relief or lube relief valve would affect system pressure? And would therefore affect reverse brake pressure also?

 

[rockcreek4630]

Those valves would show up on lube side it might affect system pressure but not that much. Yes you are looking for something just in forward any valves in common would affect both

 

[JohnS1970]

Okay thanks for your help.

 

[reuer]

Not sure how similar the transmissions are but when we lost forward gears on our 7510 with lh reverser several years ago it ended up being some broken springs. I dont recall the name of the valve but it had 3 springs under a cap held in with a snap ring on the bottom shift valve. Our springs were all broken and new springs fixed it.