Posted by Janicholson on January 24, 2009 at 06:36:25 from (68.112.156.69):
In Reply to: TA question posted by The F.N.G. on January 23, 2009 at 22:14:43:
The following is basically true. Exceptions can be found, and the blur at the transition to high HP, European, and CaseIH tractors is not included.
There are three clutches in a TA drive (and a PTO clutch)train in SMTA, X00, X50 and X60 tractors. They are the main tractor clutch controlled by the foot clutch pedal. The TA Direct drive clutch (looks, and is like a smaller regular disk clutch with a pressure plate. It is controlled by both the TA lever, and by the master clutch pedal motion. The third "clutch" is a one way clutch. (think of a quiet ratchet that allows turning one way but locks the other) it is not controlled by the operator. The main clutch is just that it operates just like a normal every day friction disk clutch. If worn, it slips, if greasy it slips/chatters, if good it holds well. it can be either composite friction material, or ceramic puck style (spider/puck). The TA direct clutch is used when the TA lever is forward. It is composite, and when engaged, it locks the TA assembly together causing it to turn as a unit. this provides direct drive. The TA direct clutch can be smaller because the torque applied to it is much smaller than total drive line torque. The one way (ramp and rollers, or sprag type)clutch operates when the TA direct clutch is disengaged. The TA planetary gears (like in an auto trans)are free to turn when they do the TA gear housing trys to turn backwards (in reaction to gear reduction inside)this retro turning is stopped b the one way clutch being attached to the frame casting of the tractors transmission. This causes the gears to turn the transmission input shaft at a reduced (~30%)speed.
If the master clutch is weak the tractor drive will slip when loaded, or starting in higher gears.
If the TA direct clutch is weak, it will slip in direct drive and seem like it goes into TA "automatically" because it will still pull like it is in TA low. (this will happen for a short time because the TA direct clutch will be toast, then it will seem like it is in TA low all the time.
If the one way clutch is getting bad, it will either sometimes work in TA low, or slip out of TA low into a neutral like don drive condition. It can also just not move in TA low when the one way clutch is toast.
The higher HP newer tractors use a four clutch system also, but the TA direct and rear TA hold clutches are hydraulically operated. This change does not affect the concept of operation.
Always move the TA lever (all kinds) rapidly into and out of TA; prettymuch as fast as possible W/O letting go of the lever.
Never use any TA to try to ues engine braking to slow. The mechanical TA is only able to free wheel in TA low and will destroy itself if coasted down a hill in gear faster than direct speed in that gear (the TA housing will spin up faster than the engine and can come unglued with explosive deterioration!!) Further, the coasting is dangerous and un controlled. The hydraulic TA will hold back on down hill coasting, and is OK to use that way!!---But-- only if you are at that speed in TA low already, never put it in TA low to try to slow down. It can slide the tires and wear out the clutches as well as break parts. Not good. This is all there is to it at a basic level.
They are 10,000 hour devices if used often and correctly. Their reputation (with good operators and proper adjustment/maintenance is golden and they are a great feature.
If ignored or used by slow lever motion or speeding down hills, they die. Then the owner blames the TA. It is exactly the same as using any sophisticated equipment. Do it well maintain it properly, and it will serve. I hope this works for you. Let me know, JimN
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