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Magnum 305 transmission pressure


CaseIH 305

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We have a 2008 Magnum 305 tractor that is giving a warning for low transmission psi, I believe anything under 270#. I have seen in other posts that it should be ~ 315#, the only time the A pillar says it’s that high is when the tractor is on park. We have cleaned the suction screen and changed the filters many times. Is there a port to install an analog gauge to confirm somewhere or pull the pressure sensor from the left side valve body between the fuel tank and transmission?

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What is the trans. pressure when the park brake is on? How much does it drop when the park brake is released? Unfortunately, its not uncommon to have park brake problems on these. 

Look over on the RH side of the transmission case in front of the rear axle. There will be a plate with a hydraulic line/plumbing going through a side cover....should be a test port there as well. Unhook the line and cap both sides. Start the engine and release the park brake....if the pressure does not drop very much now, more than likely the park brake has excessive leakage internally. The line is item #20.

 

305 park brake plumbing.png

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When I engaged the 4WD the pressure on the A pillar fluttered a few psi, I couldn’t really see how much then it would settle. So no change there. I also noticed when I apply both brake pedal’s that the 4WD light comes on no matter where the switch is or the where the F-N-R lever is. 
The transmission pressure on the A pillar is 335# while in neutral and 265# in forward or reverse. The test port only has pressure on it when in gear and appears to be the difference of the two, 75#. I removed the line and capped both sides as directed, that made no difference. The pressures remained the same and engine rpm didn’t seem to affect much either. I didn’t warm the hydraulics up before checking, I figured hotter oil would make the pressure lower. 

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41 minutes ago, CaseIH 305 said:


The transmission pressure on the A pillar is 335# while in neutral and 265# in forward or reverse. 

#335 in neutral.....or in park? Makes a big difference here. With the FNRP in park, the park brake solenoid is off, and you should more or less have full regulated/transmission system pressure here unless you would happen to have a leak in another regulated circuit like MFD disengage, diff lock engage, or PTO circuit, which it doesn't sound like you have any problems at any of these other areas. When you put the FNRP in neutral, the park brake release solenoid is powered up, but no other transmission solenoids should be powered up; you may see a small pressure drop when the park brake is released, but should be less than 5-10 psi. Putting the transmission into an operating gear will probably see the pressure drop a little bit again, nowhere close to 70 psi, though.

The MFD applying with both brake pedals pushed is normal operation....gives you 4 wheel braking that way.

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Plug the park line off like was suggested -- but does sound like the leak is in that clutch pack

park needs oil pressure to release
also is part of the 4x4 drive -- so you will be splitting the tractor

Real problem rolling the tractor apart when the park has failed
I made a fitting with a grease zerk to pump up the park brake so the tractor will roll when assembling
Shop air won't quite get the pack released

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20 minutes ago, HydroTek said:

Plug the park line off like was suggested -- but does sound like the leak is in that clutch pack

park needs oil pressure to release
also is part of the 4x4 drive -- so you will be splitting the tractor

Real problem rolling the tractor apart when the park has failed
I made a fitting with a grease zerk to pump up the park brake so the tractor will roll when assembling
Shop air won't quite get the pack released

If the tractor is going to be split that is going to be the dealers problem then. When the line was capped and put in gear I released the clutch some and I felt the park brake was engaged, I think that is the way it should’ve been working. 

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2 hours ago, HydroTek said:

Plug the park line off like was suggested -- but does sound like the leak is in that clutch pack

park needs oil pressure to release
also is part of the 4x4 drive -- so you will be splitting the tractor

Real problem rolling the tractor apart when the park has failed
I made a fitting with a grease zerk to pump up the park brake so the tractor will roll when assembling
Shop air won't quite get the pack released

I use a porta power pump to release park when needed

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There is a check valve in the park circuit for the suction of the hand pump that releases the park. Cap the line that runs from tee 19 over to the hand pump.  Seen several of those checks fail.  Regulated psi drops when pulled out of park.  

On 12/28/2023 at 10:36 PM, SDman said:

What is the trans. pressure when the park brake is on? How much does it drop when the park brake is released? Unfortunately, its not uncommon to have park brake problems on these. 

Look over on the RH side of the transmission case in front of the rear axle. There will be a plate with a hydraulic line/plumbing going through a side cover....should be a test port there as well. Unhook the line and cap both sides. Start the engine and release the park brake....if the pressure does not drop very much now, more than likely the park brake has excessive leakage internally. The line is item #20.

 

305 park brake plumbing.png

 

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1 hour ago, HydroTek said:

Yeah that would work fine -- but one porta power and six guys in the shop -- grease gun was easier in my case

We have the luxury of three OTC pumps and a larger portable hand pump with a lever that sticks straight up and pumps in both directions.

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Thanks for the parking brake information. As far I can tell the parking brake works fine and releases as it should, we don’t operate on hilly ground or pull trailers where we’ve seen it roll away. 
I’m assuming when I removed the U line (20) and capped the fittings that was checking to see if the park brake was leaking excessive pressure causing the transmission pressure to be low. This discussion has steered me away from thinking we have a pump problem and more of a valve or something internal failing. 

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7 hours ago, CRutt said:

There is a check valve in the park circuit for the suction of the hand pump that releases the park. Cap the line that runs from tee 19 over to the hand pump.  Seen several of those checks fail.  Regulated psi drops when pulled out of park.  

 

 

5 hours ago, CaseIH 305 said:

Thanks for the parking brake information. As far I can tell the parking brake works fine and releases as it should, we don’t operate on hilly ground or pull trailers where we’ve seen it roll away. 
I’m assuming when I removed the U line (20) and capped the fittings that was checking to see if the park brake was leaking excessive pressure causing the transmission pressure to be low. This discussion has steered me away from thinking we have a pump problem and more of a valve or something internal failing. 

 

4 hours ago, CaseIH 305 said:

Yes all the gears, R and 1-18 have the same low pressure, give or take a couple of pounds. 

Cap off line 10 and fitting 18 that connects the hand pump to the park release circuit.  Then see if the regulated pressure increases when in out of park.
Also, item 2 is a relief for the park brake system, not a common problem but a possibility of a leak there as well.

In the second illustration item 8 is the park check valve that can be problematic. MXMagnumParkBrakeSystem.JPG.95e10b6f00ee50b646f5098a7cdac312.JPGMXMagnumParkBrakeCheck.JPG.c5016d56c620fc95a0d3cfc2bd58dbdb.JPG

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  • 1 month later...
  • 3 months later...

Four months later,

We made an appointment with the local dealer and went over the low trans psi problem then took the tractor in February because they said they’d get it in, mid March they started on it (guess dealer time). The following is a summary of the invoice, they started off by replacing the hi psi pump because the steering psi was #1700 and wouldn’t adjust up to #1800, ok need steering. They then moved to the signal checks and cleaned them out, then to the priority valve on top of the transmission and found that the regulated spool was stuck but they had made no progress on transmission psi yet. At this point we decided to trade the tractor off for a JD but part of the deal was that the JD dealer wanted to see the invoice. They then moved to the park brake/MFD clutch circuit and found a small leak there but did not resolve the problem. (THD) who ever that is, suggested that the priority stack be replaced because the signal spool maybe sticking. Cleaned all checks and such then said it was good and called us to come pick it up.
Except while driving it home it threw the LOW TRANS PSI warning at #265 or whatever, made a call and they came over and cranked the psi to #325 and we took the tractor to the JD dealer. End result was 4 months and $36k for a problem that probably still exists. 

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  • 2 weeks later...
On 12/28/2023 at 9:04 PM, HydroTek said:

Pressure come up when you turn the 4wd on ?

I have the same problem low transmission pressure in all gears except when the 4x4 in on. When 4x4 is off I have 1900kp and when 4x4 is on I have 2400+. Can the 4x4 package leak inside?

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