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andy.jobcorps

Member
Joined
Apr 24, 2018
Messages
5
Location
White Swan, WA
Hello all, I've got a 1978 CAT 130G 9Y series grader with the 3304 engine that will not shift into either forward or reverse at any speed. Main Hydraulics work fine. So far I have checked:
Transmission Oil - Full
Transmission Filter - Replaced
Transmission pump pressure - low 250 PSI, added another spacer to relief valve group, now 300 psi
Shift cable - connected at both ends
Manual Modulation Cable - connected at both ends
Forward/Reverse Cable - connected at both ends

Any ideas you have would be appreciated. Thanks.
 

r20d12

Well-Known Member
Joined
Nov 29, 2009
Messages
123
Location
oklahoma
Occupation
heavy equipment field tech since July 1990
If the modulation pedal is malfunctioning. It will not let clutches engage. Make sure everything moves free. Actually take the cable loose on both ends and slide it back and forth by hand and make sure pedal is all the way up. Then check clutch pressures.

Hope this helps
 

20/80

Senior Member
Joined
Jul 29, 2013
Messages
881
Location
nova scotia canada
Occupation
operator
Hello all, I've got a 1978 CAT 130G 9Y series grader with the 3304 engine that will not shift into either forward or reverse at any speed. Main Hydraulics work fine. So far I have checked:
Transmission Oil - Full
Transmission Filter - Replaced
Transmission pump pressure - low 250 PSI, added another spacer to relief valve group, now 300 psi
Shift cable - connected at both ends
Manual Modulation Cable - connected at both ends
Forward/Reverse Cable - connected at both ends

Any ideas you have would be appreciated. Thanks.
What were you doing when you lost your gears? did this happen while grading or working your machine? or was the machine sitting for awhile and now your gears don't work?
 

andy.jobcorps

Member
Joined
Apr 24, 2018
Messages
5
Location
White Swan, WA
What were you doing when you lost your gears? did this happen while grading or working your machine? or was the machine sitting for awhile and now your gears don't work?

Operator reported that it came to stop on its own while grading, put it in reverse where it sluggishly rolled a bit then was dead in the water.
 

r20d12

Well-Known Member
Joined
Nov 29, 2009
Messages
123
Location
oklahoma
Occupation
heavy equipment field tech since July 1990
Sounds like you need to check pressures and then inspect the magnetic screen.
 

andy.jobcorps

Member
Joined
Apr 24, 2018
Messages
5
Location
White Swan, WA
Ok, we think we figured it out. it appears the pilot pressure tap plug at the top of the XMSN valve bank fell out in operation and is allowing the pressure to dump out of the valve.

Troubleshooting steps to date:
-Oil level checked - full
-XMSN Filter changed - old filter relatively clean
-checked all pressure taps except pilot pressure tap (difficult to access)
-Pressures - see table
-drained oil and dragged a magnet through it - clean
-the tap P2 for the direction clutch was 0 psi when it should have been approx. 200-250 psi (our pressure gauges had 30 psi error) that led us to valve level three to check the differential, safety and check valve - everything was fine
-since we had it out we disassembled and inspected the entire valve bank. - everything was fine
-at this point we were running out of easy checks and took another look at the book. forgot to check the debris screens.
-bottom debris screen had the plug for the pilot tap in it as shown in pics below - should have checked debris screen first.

it also looks like the speed clutch is starting to wear out as there were a number of bronze flakes in the screen as well.
We're still putting it back together and have yet to test it; should know tomorrow. Thanks for the help everyone.
130G XMSN Pressure Readings.JPG
IMG_5975[1].JPG IMG_5976[1].JPG IMG_5977[1].JPG
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
29,769
Location
G..G..G..Granville.........!! Fetch your cloth.
The dark pieces appear to be clutch material. Not sure about the source of the brass ones though. Could even be differential. Just to be clear, on this machine there are two identical screens, one (upper) for the differential & bevel gear compartment, the other (lower) for the transmission. Which of the two did these particles come from..?

Maybe run the machine for a while and pull the screens again to see what has accumulated.
 
Last edited:

HARRIS*1

New Member
Joined
Apr 4, 2024
Messages
1
Location
HERMISTON, OREGON
Ok, we think we figured it out. it appears the pilot pressure tap plug at the top of the XMSN valve bank fell out in operation and is allowing the pressure to dump out of the valve.

Troubleshooting steps to date:
-Oil level checked - full
-XMSN Filter changed - old filter relatively clean
-checked all pressure taps except pilot pressure tap (difficult to access)
-Pressures - see table
-drained oil and dragged a magnet through it - clean
-the tap P2 for the direction clutch was 0 psi when it should have been approx. 200-250 psi (our pressure gauges had 30 psi error) that led us to valve level three to check the differential, safety and check valve - everything was fine
-since we had it out we disassembled and inspected the entire valve bank. - everything was fine
-at this point we were running out of easy checks and took another look at the book. forgot to check the debris screens.
-bottom debris screen had the plug for the pilot tap in it as shown in pics below - should have checked debris screen first.

it also looks like the speed clutch is starting to wear out as there were a number of bronze flakes in the screen as well.
We're still putting it back together and have yet to test it; should know tomorrow. Thanks for the help everyone.
View attachment 182417
View attachment 182414 View attachment 182415 View attachment 182416
When you removed the pilot selector and pressure control valve group was there a gasket? or when you re-install it do you put any sealant between it and the transmission where it is a machined surface? it just seems strange to have nothing there?
 
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