Cat D9G Wont Move

David Greenwood · Dec 19, 2020

Hi New member here. D9G Caterpillar, we changed the oil in the transmission and now the old girl will not move. Searched the forums and found a similar situation on a D9H with a portion of a manual in a pdf on the flow of oil through the tranny, would the system be the same in the D9G? Does anyone have any perspectives on what could be causing the issue? The d9h guy resolved his issue by cleaning the priority valve and swapping out the pressure control valve. Wanted to check here before changing parts.
I have posted the manual portion the other fellow on the d9h posted
I don't know if this is allowed but if you can call my guy please do. In Saskatchewan Canada Al 13062228527
Serial number of the unit is 66A5164 Series G
Thank you

d9gdon · Dec 19, 2020

Sounds like you have an air-locked transmission pump on the right hand rear of the engine. I think there's a little plug on the back of the pump that you can take out and it should prime when you turn the engine over. If there's not a plug in the pump, take the pressure line loose at the pump and turn over the engine to prime. It will spray like hell when it primes, so be careful. I'm going by memory and it's been a while...

farmerlund · Dec 19, 2020

Not to hy-jack, but we have one that looses prime when it sits for a while. like 2-3 months. always goes after bleeding, but how do i stop it from loosing prime?

d9gdon · Dec 19, 2020

farmerlund said:
Not to hy-jack, but we have one that looses prime when it sits for a while. like 2-3 months. always goes after bleeding, but how do i stop it from loosing prime?

The little sections of rubber hoses on the suction lines get hard and brittle, then start leaking air into the system...or you could just have loose clamps. Use 2 good quality heavy duty hydraulic hose clamps on each end of the rubber section, not the light duty clamps.

Also, put new o-rings in at the pump flanges.

Shimmy1 · Dec 19, 2020

When we changed out the oil in our 7G this summer, it took a couple minutes until it primed up. Didn't expect it to not move after refilling, but eventually it did and never had any problems.

David Greenwood · Dec 20, 2020

Bled the pump I am advised oil was shooting way up in the air. What should we try next?

John C. · Dec 20, 2020

You need to check pressures in the system. I usually just plumbed a 1,000 PSI gauge into the port on the pump.

David Greenwood · Dec 20, 2020

Thanks to D9G Don and everyone else, my friend hooked up a hose to the pump prime port and after removing close to 3, 5 gallon pails of hydraulic fluid while turning the motor over it primed and now moves fine. Thanks for the help.

d9gdon · Dec 23, 2020

Sometimes we deserve an easy fix.

John C. · Dec 23, 2020

Maybe this isn't so easy yet. Why did it lose prime? Why didn't it pick it up on its own without having to vent off about 15 gallons of oil before it primed?

nicky 68a · Dec 28, 2020

Something is abit strange here.
Extremely common to loose prime after been sitting a while and I like to overfill them by a few gallon,fire them up on low idle,then walk away and leave them for half an hour.
If your chap has primed around 15 gallons off,I’m breaking out into a sweat.
Something more is wrong if that’s the case.
Is it possible your chap may be exaggerating abit?It may well have pumped a fair bit onto the moon if he tried to put the blead screw back in and failed,but 15g????

Jonas302 · Dec 28, 2020

We had an 8K that took a long time to prime had a hole in the suction strainer under the clamp never leaked a drop once it pulled up it would push good all day till you shut if off

nicky 68a · Dec 28, 2020

I had a D6C like that that never leaked either!
I fitted constant prime lines to my later D8H’s

David Greenwood · Jan 14, 2021

Hi All.
Original poster on this thread.
More troubles we are having. My friend advises he changed the hydraulic pump as the pump failed. Now the drive shaft wont turn, the engine is sluggish and wont rev up like something is binding. He did try bleeding it again. Any thoughts on this?

.RC. · Jan 14, 2021

Did he pull both clutch levers to isolate the final drives?

David Greenwood · Jan 15, 2021

I have been asked to ask how you do this, thank you

Dave Neubert · Jan 15, 2021

Just pull both steering clutch levers

David Greenwood · Jan 15, 2021

The steering clutches were tried, he thinks it may be the transmission, are there any other ideas to try
Thank you, BTW May be seeking a transmission for a d9 if anyone knows of one in Western Canada
Thanks again for any and all responses, your thought are appreciated

Simon C · Jan 15, 2021

d9gdon said:
Sounds like you have an air-locked transmission pump on the right hand rear of the engine. I think there's a little plug on the back of the pump that you can take out and it should prime when you turn the engine over. If there's not a plug in the pump, take the pressure line loose at the pump and turn over the engine to prime. It will spray like hell when it primes, so be careful. I'm going by memory and it's been a while...

View attachment 230369

Started a D7G with that plug out and the oil hit the ceiling in 1 Second when it started. Best to have small hose hooked up into 20 liter pail instead.

Simon C · Jan 15, 2021

David Greenwood said:
The steering clutches were tried, he thinks it may be the transmission, are there any other ideas to try
Thank you, BTW May be seeking a transmission for a d9 if anyone knows of one in Western Canada
Thanks again for any and all responses, your thought are appreciated

If it is air locked put air to the Tank Filler port with a rag ball over as 1 PSI of oil will push oil to pumps very well especially if the discharge side of the pump has a hose or something loosened. If it is not air locked you will have to verify if the pump is turning. Be careful or you will have a bath.

Cat D9G Wont Move

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