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Discussion Starter #1 (Edited)
A primer on PTO’s

Many a post of users having troubles engaging or keeping a Gravely pre Pro series PTO working properly.

Some knowledge and a visual of the components involved will always help in trouble shooting a problem. A fancy little guy called a ‘shipper shaft’ moves the dog gear into and out of engagement with a safety clutch drive plate. The total 'throw' of the shipper shaft is 5/8" and the depth of the drive dog plate cogs is slightly less the 1/2" Some photos, click any to enlarge.


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For Gravely newbies, it is a quick jerk required to engage the dog gear into the safety clutch drive plate, never try to 'baby it' into engagement.

Loose components and wear between the shipper shaft often cause shifting problems.

Gravely introduced a remote shifter and the first linkage components were not the best design. Many improvements in remote shifting were made, and mostly right at the main PTO components.

The very first PTO shipper shafts moved a dog gear without a trunnion block and the tip of the shipper shaft wore from use, causing problems. There is a very different style of dog gear between new and old. If a dog gear has a 'nose' in front of its cogs, then that is old style. If the dog gears shifting cogs are flush with the front face, that is new style and requires a trunion block on the tip of the shipper shaft. Old style dog gears can be replaced with new style along with a trunion block, if the tip of the shipper shaft still fits the trunion block without any slop.

Roger,
 

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Discussion Starter #3
Here is an early style dog gear, one which did not used a trunion block. The tip of the shipper shaft moved the dog gear in and out. The dog gear always turns with the engine running in H/L and there was wear on the tip of the shipper shaft, sometimes enough wear to cause shifting problems.

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Roger,
 

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Roger, since this is a sticky, can your add in pics of your mod that you did to improve the engagement on the outside?
 

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