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1256 Losing lube pressure in T/A


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Got a question I'd like to hear some ideas on. A fellow mechanic friend of mine recently put a new T/A in a 1256. Lube pressure is 19psi in Direct and T/A. Take the tractor out and run it for a while (an hour maybe) and he'll lose lube pressure completely. He's replaced the T/A again, tried another MCV and new mcv pump off an 86 series, blocked off the brake and hydraulic seat circuits and it still does it.  

That's pretty much all I know about it now. We just had a quick conversation about it this morning and I wasn't for sure what to tell him. Any ideas?

Travis

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I had a torque housing one  time that the outside oring on a jumper leaked because the transmission housing was not thick enough, I often use a light and mirror to look and make sure i don't see oring inside, on that tractor i installed a 5/16 lock washer in the torque where jumper tube goes to shim tube out a little Steve

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9 hours ago, 3588pfcred said:

I had a torque housing one  time that the outside oring on a jumper leaked because the transmission housing was not thick enough, I often use a light and mirror to look and make sure i don't see oring inside, on that tractor i installed a 5/16 lock washer in the torque where jumper tube goes to shim tube out a little Steve

I once had a jumper tube that, although it looked the same, was actually shorter.  This caused the same problem that 3588pfred experienced. 

Even though that was over 30 years ago, I still always compare the length of the jumper tubes to each other. 

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I have saw a few times over the years where the spring loaded lube baffle for the input shaft ball bearing had came out of place or got warped . This will create a lube pressure leak . The thin brass lube baffle can come out of place during installation of a TA if the hose clamp that is put around the input shaft either slips or is taken off prior to installation allowing the input shaft to slide through the TA unit housing if the housing sticks while the TA unit is being lowered into the Speed Trans housing .

Not a common thing but have seen it happen over the years .

Bob

 

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Loss of lube pressure,  FARMALL FIXER mention the brass lube baffle.  If somebody would air test the TA (top jumper tube) with shop air pressure it will warp the lube baffle and then no lube pressure.

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6 hours ago, Charlieu said:

Loss of lube pressure,  FARMALL FIXER mention the brass lube baffle.  If somebody would air test the TA (top jumper tube) with shop air pressure it will warp the lube baffle and then no lube pressure.

Yeppers , can happen with pressurizing the lube jumper tube too ,  good point I forgot to mention that one .

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What's lube pressure when TA  spool is in the middle position. If lube pressure rises in mid. position and 0 in TA or DD you have a leak in the TA unit. I would check this before doing anything.

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1 hour ago, mrfred54 said:

What's lube pressure when TA  spool is in the middle position. If lube pressure rises in mid. position and 0 in TA or DD you have a leak in the TA unit. I would check this before doing anything.

Well, as mentioned, he's already tried another T/A, and another MCV with a new pump....I'm not sure what the pressure is in the mid position, but I will pass it on to check.

On 7/6/2019 at 12:04 PM, Charlieu said:

Loss of lube pressure,  FARMALL FIXER mention the brass lube baffle.  If somebody would air test the TA (top jumper tube) with shop air pressure it will warp the lube baffle and then no lube pressure.

Considering he has lube pressure and then loses it about an hour after running the tractor, I doubt this is the issue.

 

Travis

 

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  • 1 year later...
On 7/2/2019 at 10:02 AM, Sparky said:

Got a question I'd like to hear some ideas on. A fellow mechanic friend of mine recently put a new T/A in a 1256. Lube pressure is 19psi in Direct and T/A. Take the tractor out and run it for a while (an hour maybe) and he'll lose lube pressure completely. He's replaced the T/A again, tried another MCV and new mcv pump off an 86 series, blocked off the brake and hydraulic seat circuits and it still does it.  

That's pretty much all I know about it now. We just had a quick conversation about it this morning and I wasn't for sure what to tell him. Any ideas?

Travis

So what did it turn out to be?

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Pull the MCV and and give the MCV pump a quick test . Put parts solvent or diesel fuel in the pump on the suction side , turn it over by hand and hold your thumb over the small port , if you can’t hold your thumb on the psi port the pump is good , if you hold your thumb on there the pump is bad . Just had a friend of mine with a 1086 with a new TA a year ago and a new MCV pump , the pump was ok when the oil was cold but just after a few min the lube would drop and if he he turned the steering g to the stop the steering would lock up . He capped off the brake valve , diff lock and finally figured out the pump was week .

‘Danny 

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Nice 😳 I didn’t see that 😕

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14 hours ago, jass1660 said:

This is an almost two year old post.....

But since it was never reported back what fixed it. We have a ending in that we have a very simple test, and the fix for it. Hopefully the next guy has a good starting point.

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28 minutes ago, ray54 said:

But since it was never reported back what fixed it. We have a ending in that we have a very simple test, and the fix for it. Hopefully the next guy has a good starting point.

If he can remember, I don’t recall last week....

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I don't know if Josh  needed this information or just stumbled on it, but had dug it up.  Their are some smart (lucky) (or pick some other description) that can get the search function to work and get real use from information given here. 

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I think this was in reference to our tractor, if so I removed the brake valve assembly off a parts tractor we had, he rebuilt it, and no more problems.  He thought it likely that there was an internal crack in the housing itself.  I hated that the tractor gave him such problems, I really appreciated that he kept on with it until the end.

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