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Farmall 400 TA questions

N

Nebraska Kirk

Well-known Member
I was adjusting the TA on my Farmall 400 when it dawned on me that if I have everything adjusted correctly, then the TA clutch throwout bearing will always be touching the clutch fingers and spinning whenever the engine is running and main clutch engaged. Is this the way it is supposed to be?
 
No, if it is adjusted properly the throwout bearing will not be touching fingers when in direct drive, they will be when in TA but then the TA clutch will not be turning. Back to the drawing board.
 
Thanks, Pete. I read through the adjust procedure in my manual again and found out where I went wrong. I will readjust it in the morning.

Another observation.
Power from the engine goes through the main clutch and when in direct drive, through the TA clutch. Now, the 7" TA clutch pressure/backing plate is fastened to the clutch carrier with 6, 1/4" bolts, whereas the 12" main clutch pressure/backing plate is bolted to the flywheel with 6, 1/2" bolts, it seems to me that the 6, 1/4" bolts on the TA clutch are somewhat inadequate.
 
Looking at the difference in sizes of the two clutches would make one wonder how come the TA can get by with a smaller disk.

The reason is that the TA clutch does not have to hold as much torque as the main clutch because of the gear reduction in the TA. The power is transmitted through the TA gears to the input shaft of the transmission. As the TA reduces the output shaft speed the torque entering the transmission is greater than the torque coming through the main clutch. Since torque is increased as speed is decreased, the opposite is also true. The gearing in the TA has the effect of trying to increase the speed of the TA clutch assembly and thus reducing the torque available. The result is that the TA clutch, even though it is smaller, is able to handle as much HP as the main clutch.
 
I have never heard of them breaking. I have the opposite problem. Hard to keep the bearing off the fingers on the main clutch on my 460. Some slop in the linkage requires the adjustment to be close. They do not touch at idle, but centrifugal force puts them against the fingers at operating rpm. Check every connection for too much play. One thing you can do is replace all the pins. I also had some of the holes in the clevices filled -- did not completely cure the problem. Although not recommended, you can adjust the fingers, also. You may have to deviate from "by the book" to get it to adjust it right. Just be sure the TA disengages when the main clutch is disengaged. And that it releases when you pull the TA lever back.
 

Owen, but the TA clutch is disengaged when the TA is in low. With the TA clutch engaged, there is no gear reduction through the TA. Maybe I am missing something but it seems to me that the same amount of torque is going through the TA clutch as the main clutch.
 
My brain is old and tired, but, the TA unit spins as a whole when in direct, so the main clutch and the TA clutch are turning the same speed in direct?
 
(quoted from post at 22:34:02 02/11/10)
Owen, but the TA clutch is disengaged when the TA is in low. With the TA clutch engaged, there is no gear reduction through the TA. Maybe I am missing something but it seems to me that the same amount of torque is going through the TA clutch as the main clutch.
Click to expand...

Ah, that is where it gets a little tricky. The power coming into the TA is on the sun (small input) shaft. It is meshed with the three planetary gears which are also meshed with the transmission input shaft. As the sun shaft rotates, the planetary gears are also forced to rotate. The planetary gears are fastened to the carrier by the three small shafts. The resistance of the transmission input shaft causes the planetary gears to try to turn the carrier instead of the them turning transmission input shaft. With the TA clutch released, as long as the ramp and rollers hold the carrier, the planetary gears will turn the transmission input shaft with a geared reduction in speed.

The TA clutch connects the sun gear with the carrier assembly. That give two paths of power transmission through the TA assembly, one through the sun gear to the planetary gears, the other through the carrier to the planetary gears. The force is split between them so that there is only about half the torque going through the TA clutch as there is through the main clutch.
 
Thank you for the explanation, Owen. I still don't understand it fully, but IH spent a lot of $$ in research and development on the TA and it obviously works and does the job it was designed to do.
 
I have seen them throw that 7 inch clutch right through the top cover, however this happens when you are appling the torque from the other end like in pull starting the tractor. You know, pulling it while in ta, realizing it isn't turning the engine and then dropping the ta lever ahead, bang.
 
The original disk had a lining that was riveted to the disk. If you allow the tractor to free wheel down a hill you can easily over speed the disk to the point where the ling will be thrown off. When that happens you will lose the high, direct, side of the TA.
 
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