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Hello to all,

This is my first post so bear with me !

I have a 1987 684 which has developed problems with the TA over recent months, when first starting the engine the machine will "usually" drive ok in either direct or TA mode but after a very short distance or if the TA lever is moved between ranges the drive will stop, moving the lever after this point does not sort the problem but pressing clutch pedal down will mostly restore drive! whenever the drive is lost it is nearly always pressing the clutch pedal that restores it (there is no problem with the clutch itself, drives and clears ok) 

I fitted a pressure gauge to the tapping in the bottom plate and got about 210 psi (230-270 required) so I added shims to the pressure regulator to get it up to 270 psi.

None of the above has altered anything! I would have thought if the TA unit was worn or damaged the fault would be constant ie no drive in TA.

Any suggestions before splitting the tractor would be most helpful.

Blastapest.

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4 hours ago, Blastapest said:

I have a 1987 684

You can't.  IH built the 684 and production stopped in 1983.  If it is a 1987, it is a 685.  If it is a 684, it isn't a 1987.  So, do you have a 684, or 685?  Not much difference, but you need to know what you have.  The year of the machine is completely irrelevant anyway. 

The T/A in that series was backwards.  T/A (lever back) was direct drive and forward was a gear increase, or overdrive.  Anyway, what does the gauge do as you are driving it and it stops?  Your description of using the clutch and then it goes back to working makes me think a sprag is not holding, but I do not recall if it uses a sprag in both low and high.  Does steering quit when it stops moving? 

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85's had a switch not a lever. There is one sprag two clutches one piston. Lockup clutches are applied by return spring on hydraulic piston. Sprag and lock ups on ta side. At least I think so. Won't argue with anyone who says different.

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24 minutes ago, snoshoe said:

85's had a switch not a lever.

I thought they still had a lever? I don't think I ever worked on an 85 with a T/A, but did work on them with the shuttle.  Pretty sure it still had the lever, but that's been 20 years ago. I won't argue either.  I would have to look it all up. 

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5 hours ago, J-Mech said:

I thought they still had a lever? I don't think I ever worked on an 85 with a T/A, but did work on them with the shuttle.  Pretty sure it still had the lever, but that's been 20 years ago. I won't argue either.  I would have to look it all up. 

I had to look this up myself as I've never seen a lever TA 85 series, but have driven toggle switch shift ones.  

The EARLY 685s could have a lever TA, I suspect these ones have the offset driveshaft ZF axle

https://www.messicks.com/cas/97545?sectionId=236046&diagramId=4088BD68-8FBF-E111-9FCE-005056875BD6

The later ones were the electric switch

https://www.messicks.com/cas/97545?sectionId=236024&diagramId=1989BA70-8FBF-E111-9FCE-005056875BD6

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Am I correct, that there were early 685's with Z-shift pattern and lever T/A's? Later ones had H-shift pattern and electric shift T/A's with the 4 wire clutch safety switch that 2 wires were to shift the T/A into LO when the clutch was depressed. I know my brother's 3230 with electric T/A works that way, his 495 has H-shift but no T/A. I don't believe the electric T/A shift have the separate T/A pump in the bottom of the torque tube but use the a supply from MCV like the fast reverse option? Is this correct? I don't have a service manual for the 3230 only the 684 and older.

Here is my experience with a 684 with Z-shift and Lever T/A with a bad T/A:
HI would always drive or hold back on a hill but if you shut the tractor off with T/A in HI and transmission in a low gear on a hill after a period of time the tractor would start to roll down the hill. My theory was the check valve in the T/A pump was leaking. 
LO, if you pulled T/A into LO going up a hill it would lockup and pull but when over the hill and you shifted back into HI sometimes HI would not lockup and you had to push the clutch in and out and then it would lockup in HI, eventually got so bad you had to come to a complete stop, clutch, shift T/A LO to HI to get it to lockup.

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8 hours ago, jimb2 said:

Am I correct, that there were early 685's with Z-shift pattern and lever T/A's? 

All 685 had H shift. The change from Lightning Bolt / Z shift to H shift occurred in the 84 series around 1982/1983, or when the side panels went solid red (IH called these the 85 series in UK, but still 84 series here) 

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