Low track power

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jkinder
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Low track power

Post by jkinder » Tue Jun 26, 2018 11:27 am

I am new to the forum. Looking for a good contact for figuring out the movement trouble on my JD450 crawler loader.

I have a transmission pressure gauge attached to the plug hole in between the steering levers. When engine first starts
up I have no pressure until I let go of the clutch it then bounces to 130 psi. The machine will move in L,H, and R and when moving I have 130 psi. As soon as I load the machine down the pressure drops to 0 or at least next to nothing.

Last year when I purchased the machine, it would do this only in L, so I did all my work in H. I blew a hose in front of the radiator by the oil filter and since then I have no H power either. Reverse is a bit more responsive but I also notice it has lost some power can't back up on a hillside like before.

I consider loading the crawler by sticking the bucket to the ground or pushing into a dirt pile to scoop. Or if i fill the
bucket and try to go up and incline - no power. The engine never stalls, it just stop moving.


I know to check those pressures and I have drained the transmission fluid and pulled the screen on right side of transmission it was clean in fact spotless. My next step was to play with the shims at top of the transmission but I think
if I am getting 130 psi at times than that may not do any good.

Any help is aprreciated,
Jeff Kinder
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psprague
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Re: Low track power

Post by psprague » Tue Jun 26, 2018 5:36 pm

Howdy!

My 'b' book says 170 to 180 PSI warmed up to temp @1800 RPM and you already sound familiar with the shims in the clutch valve.

There also should be a pressure differential across the cooler as well.

-paul

p.s. all bets are off if there is any acorns or blue goo around.
JD 450c forestry, JD 440A cable skidder

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jkinder
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Re: Low track power

Post by jkinder » Sat Jul 14, 2018 11:31 am

I installed gauges at the cooler this morning. I have 110 in 60 out at about 1/2 throttle. At full throttle 120 and 70. That seems to function ok.

I added all the shims I could and still get the cap back on at the top of transmission. I am at 150 when moving, There is oil at the 1/4 in pipe nipple for my gauge connection that I cannot stop from coming out it pools at the top around the bung hole. When the machine stops moving and the pressure at the top of transmission goes to 0 the oil at the plug pulls into a suction back in the transmission case.

Still don't know where to go from this point.

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psprague
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Re: Low track power

Post by psprague » Sat Jul 14, 2018 12:09 pm

Oil pressure at the bung hole.

Did you remove and re-install a 1/4 inch plug under the bung plug where you had the pressure gauge? That should not fountain oil with just the big plug out.
JD 450c forestry, JD 440A cable skidder

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jkinder
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Re: Low track power

Post by jkinder » Sun Jul 15, 2018 10:00 am

I kept the connection for the oil pressure gauge in place when testing. The oil was pooling around it from my connection I did not put the pipe plug back in the pressure gauge hole. As I was testing the pressure, oil was pooling around it and then sucking back in at 0 psi.

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psprague
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Re: Low track power

Post by psprague » Sun Jul 15, 2018 10:14 am

The pressure regulator, cooler bypass and the lube dump valve seem to be giving you fairly regulated pressure readings. So dropping to 0 indicates a blockage or starvation...

When you say 'load the machine down' you mean as in pushing hard at operating RPM, yes? While doing this, the engine RPMs remain constant or bogs down or revs up when pressure drops?

Care to take a quick video? I have one with the pressure gauge installed and I shift and drive it around. LMK and I'll find the link.
JD 450c forestry, JD 440A cable skidder

Cle Elum John
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Re: Low track power

Post by Cle Elum John » Sun Jul 15, 2018 2:06 pm

I just went through a lot of that. The pooling oil may not be leakage from the pressure fitting. If you look just below the 1/8in pipe fitting there is a vent on top of the transmission case. The pool of fluid you are seeing may be the result of internal splash coming up through the vent. Take a careful look the vent is hard to see. Mine had a fine mist coming out of it and it did pool. This is normally contained by the bung cover.

About the pressure. I have two manuals, both are for the 450(). The first was an early version of the manual bought off Ebay and it says 120psi. The second is a very tattered copy of the manual that came with the dozer, it recommends 140-150psi at 2500rpm when the trans is hot. It also includes the note and I will quote exactly "Note: Early units ( -13869) were set for a lower pressure (120psi). Increase the pressure to 140-150 for extra torque capacity". I am not sure if this is even the latest version of the manual so there may be some later information out there. I also searched around and saw a number of recommendations for 160psi. I don't know if these were based on someone's personal experience, a later version of the manual, a different model of the 450(?) or just people misremembering.

Mine is set a little high (155psi) but it seems fine. It does not hit 155psi until about 2200rpm. At 1000 or 1200rpm it is 130-140 or so. I was thinking of pulling a shim out. At full pressure you can see the pressure relief valve popping on the gauge once or twice a second.

Lastly, this is a new machine to me. There are guys will a lot more practical experience with this machine than me. All I know is what I have read and seen on my dozer. If an expert tells you something different, he may have better information.

It's all I know and I hope it helps
John
Reporting from the Peoples Republic of Washington State.

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jkinder
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Re: Low track power

Post by jkinder » Wed Jul 18, 2018 11:44 pm

I have set up a couple you tube videos to show me power trouble.
https://youtu.be/Edvkbk824xU
https://www.youtube.com/watch?v=6TejW1hmfm8

Take a look, a picture is worth a thousand words, a video maybe a million.

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psprague
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Re: Low track power

Post by psprague » Thu Jul 19, 2018 6:59 am

Sorry, I meant to come back and post this.

I made a vid a while back with a gauge on my test port.
JD 450c forestry, JD 440A cable skidder

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psprague
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Re: Low track power

Post by psprague » Thu Jul 19, 2018 11:04 am

Some quick questions.

What model is this? I think I hear you say 60's and from the serial numbers listed here, it would be a straight model?

If you tip the bucket and bury the teeth in the ground, will it pull backward?

-paul
JD 450c forestry, JD 440A cable skidder

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