640 PTO Lever Disengages

First, thanks to all who helped with the steering issue on my 640. Pretty much got that one licked except I think I'm one gear off on the sectors. Turns left tighter than right.

My new question is about the PTO lever disengaging while brush hogging grass. I checked the archives but not a whole lot that I could find. Suggestions were 1. Loose snap ring for PTO shaft; 2. Loose tranny bearings; 3. Something about a spring loaded ball valve!?

Any help would be much appreciated. Thanks!

check for thrust play at the ptoi shaft.

engine off. grab shaft stub and see if there is in/out play ( or side to side too. )

Hi Soundguy. Thanks for getting back. So if there is play, then what? Check the snap ring? Thanks!

if there is side play.. beairng is going... this will hog the seal out, and if allowed to go out will cause other problems... if no thrust play yet.. just wait.

if there is thrust play, could be bearing going. or could be slipepd seal wear ring. or could be broke split ring, or could be popped out split ring, or could be damaged bearing carrier.

Take yer pic. any of those can cause the pto shaft to walk out of engagement. A bad detent could do it too , thru vibration..e tc... I've seen more broke split rings than bad detents... just sayin..

Now. if the split ring popped out.. you may or may not be able to just pop back in and go. sometiems the bearing carrier is visibly damaged with a ridge of metal removed so there is no land for the ring left. other times there is just an edge removed where the ring shoved out.. and while it may hold a bit.. it will push out easier next time... sometiems you are just living right and you put it back in and it's fine..

causes for this can be that the telescoping pto shaft on a mower, etc was either too log so that when collapsed it shoved the tractor pto stub into the bearing carrier, .. or that the shafts were rusted and when it needed to extend, instead it tugged on the pto stub. either will pop snap rings.

gain. bearing could be worn and allow the play.

shaft passes thru hyds and diffy sump.. so drain both to pull shaft.

4 bolt job and should slide right out. be carefull removing it and reinstalling. as said there is a mid sump seal.. so try to support the shaft going in and coming out so you don't hog the seal out.. they usualy leak a bit anyway.. but if you pop the lip.. it will allow mixing straight thru.. most people use utf in both sumps due to this.

once you pull here.. it is a 15m job to pull split rings.. drop bearing carrier off shaft assy, drive seal out. clean.. inspect.. reseal.. reseat wear ring if needed, if it moved, inspect bearing.. etc.

reassemble.. and clean gasket surface. regasket and go.

replacing the bearing and wear ring would add another 10m maybee.. or less if you've done 20 of them.. etc..

now the complications.

1, do check the detend.. if should be somewhat positive. if it's sloppy. fix that too.

2, if it has been allowed to walk out of engagement often / for years. the splines and couple will wear and not play nice together at some point.. requiring a front of rear end split.. walking out of engagement is bad. you may have seen some people bunji a pto selector in. this is a bandaid.. but at least keeps a shaft from walking out even if it is way out of spec on thrust paly. IMHO.. a bunji to hold one in, is only to finish that dayus mowing after that. pull and fix or don't use it.

post back if you hit a snag.

Thanks for the quick reply soundguy! I'll check all of that out and post back. I've had the tractor for about 4 years now and it's pretty much done that the whole time. So...wanting to get the task at hand accomplished, naturally, I used a heavy copper wire to hold it and mowed. The heavier the mowing, the more it's apt to pop out. I will inspect everything in your outstanding answer and post back. Congratulations! You have now provided the most detailed answer for the archives on this subject for this tractor than anyone else! Thanks!

Doug (OH)

the data is probably all inthe archives.. it's just difficult to keyword search.

good luck.

if you have been holding it in and not letting it pop out.. i hope the splines are good.

rear pto bearing carrier will be the only other major player in the game.. lets hope you find thrust play and it's a snapring or 110$ shaft assy at worst, and it slides in and is positive.

that's a best case scenerio IMHO. IE. simple thrust play correction with no extra damage.

best of luck, post back

The data might be all in the archives, but I'm not sure if it's all in one place! Thanks. I'll check it out. Fingers crossed. I feel much more prepared to attack it now. BTW, Tom Petty's a florida boy, isn't he? Talk about sound. His concerts and Discs are mixed to perfection! Yeh for the apple sound folks out there!

Doug (OH)

gainesville area.. about 45-60m north of me.

hi doug in OHIO I have 2 640s and both are doing the disengage thing.I have had the stop out of the shifter and found it worn pretty much.so I changed it helped some but didn,t fix the problem.Let us know what fixes yours and I will do the same when mine is fixed.