1984 jd 640 transmission problem

[Branson1822]

OK this is my first post here so any help would be appreciated. I have a 1984 John Deere 640 and ran perfect no problems shifted fine. Everything was fine finished The job went back a couple weeks later to get the skidder to move to the next job and I have no gears, lost all the gears, it jerks when you put it in gear but no gears i check the filter check the screen checked the fuild level but still nothing. Thanks again for any help.

 

[mg2361]

Welcome to HEF Branson!

Is the clutch disconnect engaged? That would be the lever under your main clutch pedal, IIRC.

 

[Branson1822]

No it’s not I pulled motor thinking that something happen there but it is fine

 

[Diesel Dave]

Maybe an issue with the inching pedal linkage (roll pin #1 may have sheared) or sticking internal valve at the transmission clutch valve. https://partscatalog.deere.com/jdrc/sidebyside/equipment/66805/referrer/navigation/pgId/5959 .
.

 

[Branson1822]

Ok thanks I’ll take a look I just thought it’s weird that is was fine and then all the gears went

 

[Branson1822]

can I check the pressure here

 

[Diesel Dave]

Yes.
Clutch, brake engagement chart below.
.

 

[Branson1822]

thank you I’m assuming where it says just for example 1st forward and then it got an X c one and XB one and an XC3 check all three of them separately while in first gear I’m assuming that’s what I’m supposed to do

 

[Branson1822]

Also, do you know what the pressures are supposed to be? Thanks again for your help

 

[Diesel Dave]

Also, do you know what the pressures are supposed to be? Thanks again for your help

175-185 psi.

 

[Branson1822]

Ok thank you very much

 

[Branson1822]

OK, so do I check the two I have circled for pressure or I think there’s four of them on the bottom of it. I’m just getting around to checking.

 

[Diesel Dave]

 

[Diesel Dave]

Not sure if you are able to physically reach the transmission clutch valve.
There is a test port marked “ CLUTCH “. The port is regulated pressure after the transmission pump. 175-185 psi.…
.

 

[Branson1822]

Ok thank you that’s a big help

 

[Branson1822]

Last question and I won’t bug you no more shift valve position up down What does that exactly mean? Sorry the transmission thing new to me.

 

[Diesel Dave]

Last question and I won’t bug you no more shift valve position up down What does that exactly mean? Sorry the transmission thing new to me.

The chart is showing the various shift valve position combinations to direct the pressure oil to the required clutch and or brake packs for the selected gear…
.
Interested to see the results of the pressure tests.

 

[Branson1822]

Yea me to I’ll let you know tomorrow. I didn’t have the right fitting for my gauge

 

[Branson1822]

Do I check with brake on or off and clutch in or out

 

[Diesel Dave]

Do I check with brake on or off and clutch in or out

Brake off, clutch pedal out.
Under normal operation with the clutch valve in , the pressure is cut off to clutches C1 and C2.