Re: Durability of TA

Posted by joe on June 19, 2002 at 09:51:40 from (66.43.207.226):

In Reply to: Durability of TA posted by Hugh MacKay on June 19, 2002 at 01:48:39:

the sprag is basically the roller clutch in the TA, from what i understand. I have rebuilt one of these, so i know a teeny bit about this. I will try to give a quick overview:
In high range, there is a disk clutch, like your flywheel clutch, that engages. This causes the entire TA unit to spin, and produces a ratio of 1:1.
In low range, the disk clutch become disengaged. This causes the planetary gears and sun gears and whatnot to do their thing. EXCEPT - if you just let a planetary unit sit there with power through it, the inner gears will rotate like they are supposed to, but if there is any load on the output shaft, the outside of the planetary unit will just spin backwards. This is why the sprag is needed - it is a roller clutch, that keeps the outside of the planetary unit from rotating backwards. This causes it to be held still in the low range, and to freely rotate in the high range, to get your 1:1 ratio. In low range, there is about a 1.4:1 ratio, I believe. But in any case, since the sprag allows the whole TA to rotate forwards in high range, it does the same in low range, if you are going down a hill where there is no load on the TA output - thus, freewheeling.

I sincerely hope you can follow this, LOL. Sorry for the long post.

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