installing pto

[brian s]

i am getting ready to install a pto for a front winch and i see that they sell gaskets to mount it to the trans in .010'' thickness.
do you have to shim the pto for proper gear mesh ??
thanks

 

[zebedee]

Yes - you are looking to get a 'fit' of the gears that is not 'tight'. There is supposed to be some "backlash" which means a slight gap between the teeth when going from drive to overrun. Too much gap will create noisy operation and premature wear of the teeth and too little gap means friction and constant loading of the shaft bearings and premature wear there.
You can get away with 'feel' of the back lash. Fit the pto with just one gasket or shim, then with the pto engaged, operate the pto output with your hand. Rotate the output as if you were trying to turn the drive with the engaged pto. If you cannot feel any slack as you rotate the output back and forth, then you need to remove the pto and add one shim. Repeat the test until you can feel a little slack between drive and overrun. It's like wheel bearings - not tight, just a tiny bit of 'free play'.

 

[brian s]

sounds good that was what i was thinking but was not sure.
thank you

 

[zebedee]

Look at the space on the back side of the teeth that are in contact with each other. That space is back lash and only needs to be "perceptible" to feel.

There are plenty of pictures on google - "gears meshing backlash". Good luck.

 

[m16ty]

It's all but impossible to set backlash with a dial indicator (as the tm says) with the trans in the truck. There's just not enough room between the frame and PTO to get the indicator in there.
I always do it by feel, you just need a little movement but you also have to take into account the backlash already inside the PTO. It's better to be a little too loose than too tight.